skin care model essay

• Research article
• Open access
• Published: 12 June 2019

The impact of skin care products on skin chemistry and microbiome dynamics

• Amina Bouslimani 1   na1 ,
• Ricardo da Silva 1   na1 ,
• Tomasz Kosciolek 2 ,
• Stefan Janssen 2 , 3 ,
• Chris Callewaert 2 , 4 ,
• Amnon Amir 2 ,
• Kathleen Dorrestein 1 ,
• Alexey V. Melnik 1 ,
• Livia S. Zaramela 2 ,
• Ji-Nu Kim 2 ,
• Gregory Humphrey 2 ,
• Tara Schwartz 2 ,
• Karenina Sanders 2 ,
• Caitriona Brennan 2 ,
• Tal Luzzatto-Knaan 1 ,
• Gail Ackermann 2 ,
• Daniel McDonald 2 ,
• Karsten Zengler 2 , 5 , 6 ,
• Rob Knight 2 , 5 , 6 , 7 &
• Pieter C. Dorrestein 1 , 2 , 5 , 8  

BMC Biology volume  17 , Article number:  47 ( 2019 ) Cite this article

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Use of skin personal care products on a regular basis is nearly ubiquitous, but their effects on molecular and microbial diversity of the skin are unknown. We evaluated the impact of four beauty products (a facial lotion, a moisturizer, a foot powder, and a deodorant) on 11 volunteers over 9 weeks.

Mass spectrometry and 16S rRNA inventories of the skin revealed decreases in chemical as well as in bacterial and archaeal diversity on halting deodorant use. Specific compounds from beauty products used before the study remain detectable with half-lives of 0.5–1.9 weeks. The deodorant and foot powder increased molecular, bacterial, and archaeal diversity, while arm and face lotions had little effect on bacterial and archaeal but increased chemical diversity. Personal care product effects last for weeks and produce highly individualized responses, including alterations in steroid and pheromone levels and in bacterial and archaeal ecosystem structure and dynamics.

Conclusions

These findings may lead to next-generation precision beauty products and therapies for skin disorders.

The human skin is the most exposed organ to the external environment and represents the first line of defense against external chemical and microbial threats. It harbors a microbial habitat that is person-specific and varies considerably across the body surface [ 1 , 2 , 3 , 4 ]. Recent findings suggested an association between the use of antiperspirants or make-up and skin microbiota composition [ 5 , 6 , 7 ]. However, these studies were performed for a short period (7–10 days) and/or without washing out the volunteers original personal care products, leading to incomplete evaluation of microbial alterations because the process of skin turnover takes 21–28 days [ 5 , 6 , 7 , 8 , 9 ]. It is well-established that without intervention, most adult human microbiomes, skin or other microbiomes, remain stable compared to the differences between individuals [ 3 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].

Although the skin microbiome is stable for years [ 10 ], little is known about the molecules that reside on the skin surface or how skin care products influence this chemistry [ 17 , 18 ]. Mass spectrometry can be used to detect host molecules, personalized lifestyles including diet, medications, and personal care products [ 18 , 19 ]. However, although the impact of short-term dietary interventions on the gut microbiome has been assessed [ 20 , 21 ], no study has yet tested how susceptible the skin chemistry and Microbiome are to alterations in the subjects’ personal care product routine.

In our recent metabolomic/microbiome 3D cartography study [ 18 ], we observed altered microbial communities where specific skin care products were present. Therefore, we hypothesized that these products might shape specific skin microbial communities by changing their chemical environment. Some beauty product ingredients likely promote or inhibit the growth of specific bacteria: for example, lipid components of moisturizers could provide nutrients and promote the growth of lipophilic bacteria such as Staphylococcus and Propionibacterium [ 18 , 22 , 23 ]. Understanding both temporal variations of the skin microbiome and chemistry is crucial for testing whether alterations in personal habits can influence the human skin ecosystem and, perhaps, host health. To evaluate these variations, we used a multi-omics approach integrating metabolomics and microbiome data from skin samples of 11 healthy human individuals. Here, we show that many compounds from beauty products persist on the skin for weeks following their use, suggesting a long-term contribution to the chemical environment where skin microbes live. Metabolomics analysis reveals temporal trends correlated to discontinuing and resuming the use of beauty products and characteristic of variations in molecular composition of the skin. Although highly personalized, as seen with the microbiome, the chemistry, including hormones and pheromones such as androstenone and androsterone, were dramatically altered. Similarly, by experimentally manipulating the personal care regime of participants, bacterial and molecular diversity and structure are altered, particularly for the armpits and feet. Interestingly, a high person-to-person molecular and bacterial variability is maintained over time even though personal care regimes were modified in exactly the same way for all participants.

Skin care and hygiene products persist on the skin

Systematic strategies to influence both the skin chemistry and microbiome have not yet been investigated. The outermost layer of the skin turns over every 3 to 4 weeks [ 8 , 9 ]. How the microbiome and chemistry are influenced by altering personal care and how long the chemicals of personal care products persist on the skin are essentially uncharacterized. In this study, we collected samples from skin of 12 healthy individuals—six males and six females—over 9 weeks. One female volunteer had withdrawn due to skin irritations that developed, and therefore, we describe the remaining 11 volunteers. Samples were collected from each arm, armpit, foot, and face, including both the right and left sides of the body (Fig.  1 a). All participants were asked to adhere to the same daily personal care routine during the first 6 weeks of this study (Fig.  1 b). The volunteers were asked to refrain from using any personal care product for weeks 1–3 except a mild body wash (Fig.  1 b). During weeks 4–6, in addition to the body wash, participants were asked to apply selected commercial skin care products at specific body parts: a moisturizer on the arm, a sunscreen on the face, an antiperspirant on the armpits, and a soothing powder on the foot (Fig.  1 b). To monitor adherence of participants to the study protocol, molecular features found in the antiperspirant, facial lotion, moisturizer, and foot powder were directly tracked with mass spectrometry from the skin samples. For all participants, the mass spectrometry data revealed the accumulation of specific beauty product ingredients during weeks 4–6 (Additional file  1 : Figure S1A-I, Fig.  2 a orange arrows). Examples of compounds that were highly abundant during T4–T6 in skin samples are avobenzone (Additional file  1 : Figure S1A), dexpanthenol (Additional file  1 : Figure S1B), and benzalkonium chloride (Additional file  1 : Figure S1C) from the facial sunscreen; trehalose 6-phosphate (Additional file  1 : Figure S1D) and glycerol stearate (Additional file  1 : Figure S1E) from the moisturizer applied on arms; indolin (Additional file  1 : Figure S1F) and an unannotated compound ( m/z 233.9, rt 183.29 s) (Additional file  1 : Figure S1G) from the foot powder; and decapropylene glycol (Additional file  1 : Figure S1H) and nonapropylene glycol (Additional file  1 : Figure S1I) from the antiperspirant. These results suggest that there is likely a compliance of all individuals to study requirements and even if all participants confirmed using each product every day, the amount of product applied by each individual may vary. Finally, for weeks 7–9, the participants were asked to return to their normal routine by using the same personal care products they used prior to the study. In total, excluding all blanks and personal care products themselves, we analyzed 2192 skin samples for both metabolomics and microbiome analyses.

Study design and representation of changes in personal care regime over the course of 9 weeks. a Six males and six females were recruited and sampled using swabs on two locations from each body part (face, armpits, front forearms, and between toes) on the right and left side. The locations sampled were the face—upper cheek bone and lower jaw, armpit—upper and lower area, arm—front of elbow (antecubitis) and forearm (antebrachium), and feet—in between the first and second toe and third and fourth toe. Volunteers were asked to follow specific instructions for the use of skin care products. b Following the use of their personal skin care products (brown circles), all volunteers used only the same head to toe shampoo during the first 3 weeks (week 1–week 3) and no other beauty product was applied (solid blue circle). The following 3 weeks (week 4–week 6), four selected commercial beauty products were applied daily by all volunteers on the specific body part (deodorant antiperspirant for the armpits, soothing foot powder for the feet between toes, sunscreen for the face, and moisturizer for the front forearm) (triangles) and continued to use the same shampoo. During the last 3 weeks (week 7–week 9), all volunteers went back to their normal routine and used their personal beauty products (circles). Samples were collected once a week (from day 0 to day 68—10 timepoints from T0 to T9) for volunteers 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, and 12, and on day 0 and day 6 for volunteer 8, who withdraw from the study after day 6. For 3 individuals (volunteers 4, 9, 10), samples were collected twice a week (19 timepoints total). Samples collected for 11 volunteers during 10 timepoints: 11 volunteers × 10 timepoints × 4 samples × 4 body sites = 1760. Samples collected from 3 selected volunteers during 9 additional timepoints: 3 volunteers × 9 timepoints × 4 samples × 4 body sites = 432. See also the “ Subject recruitment and sample collection ” section in the “ Methods ” section

Monitoring the persistence of personal care product ingredients in the armpits over a 9-week period. a Heatmap representation of the most abundant molecular features detected in the armpits of all individuals during the four phases (0: initial, 1–3: no beauty products, 4–6: common products, and 7–9: personal products). Green color in the heatmap represents the highest molecular abundance and blue color the lowest one. Orange boxes with plain lines represent enlargement of cluster of molecules that persist on the armpits of volunteer 1 ( b ) and volunteer 3 ( c , d ). Orange clusters with dotted lines represent same clusters of molecules found on the armpits of other volunteers. Orange arrows represent the cluster of compounds characteristic of the antiperspirant used during T4–T6. b Polyethylene glycol (PEG) molecular clusters that persist on the armpits of individual 1. The molecular subnetwork, representing molecular families [ 24 ], is part of a molecular network ( http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=f5325c3b278a46b29e8860ec5791d5ad ) generated from MS/MS data collected from the armpits of volunteer 1 (T0–T3) MSV000081582 and MS/MS data collected from the deodorant used by volunteer 1 before the study started (T0) MSV000081580. c , d Polypropylene glycol (PPG) molecular families that persist on the armpits of individual 3, along with the corresponding molecular subnetwork that is part of the molecular network accessible here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=aaa1af68099d4c1a87e9a09f398fe253 . Subnetworks were generated from MS/MS data collected from the armpits of volunteer 3 (T0–T3) MSV000081582 and MS/MS data collected from the deodorant used by volunteer 3 at T0 MSV000081580. The network nodes were annotated with colors. Nodes represent MS/MS spectra found in armpit samples of individual 1 collected during T0, T1, T2, and T3 and in personal deodorant used by individual 1 (orange nodes); armpit samples of individual 1 collected during T0, T2, and T3 and personal deodorant used by individual 1 (green nodes); armpit samples of individual 3 collected during T0, T1, T2, and T3 and in personal deodorant used by individual 3 (red nodes); armpit samples of individual 3 collected during T0 and in personal deodorant used by individual 3 (blue nodes); and armpit samples of individual 3 collected during T0 and T2 and in personal deodorant used by individual 3 (purple nodes). Gray nodes represent everything else. Error bars represent standard error of the mean calculated at each timepoint from four armpit samples collected from the right and left side of each individual separately. See also Additional file  1 : Figure S1

To understand how long beauty products persist on the skin, we monitored compounds found in deodorants used by two volunteers—female 1 and female 3—before the study (T0), over the first 3 weeks (T1–T3) (Fig.  1 b). During this phase, all participants used exclusively the same body wash during showering, making it easier to track ingredients of their personal care products. The data in the first 3 weeks (T1–T3) revealed that many ingredients of deodorants used on armpits (Fig.  2 a) persist on the skin during this time and were still detected during the first 3 weeks or at least during the first week following the last day of use. Each of the compounds detected in the armpits of individuals exhibited its own unique half-life. For example, the polyethylene glycol (PEG)-derived compounds m/z 344.227, rt 143 s (Fig.  2 b, S1J); m/z 432.279, rt 158 s (Fig.  2 b, S1K); and m/z 388.253, rt 151 s (Fig.  2 b, S1L) detected on armpits of volunteer 1 have a calculated half-life of 0.5 weeks (Additional file  1 : Figure S1J-L, all p values < 1.81e−07), while polypropylene glycol (PPG)-derived molecules m/z 481.87, rt 501 s (Fig.  2 c, S1M); m/z 560.420, rt 538 s (Fig.  2 c, S1N); m/z 788.608, rt 459 s (Fig.  2 d, S1O); m/z 846.650, rt 473 s (Fig.  2 d, S1P); and m/z 444.338, rt 486 s (Fig.  2 d, S1Q) found on armpits of volunteers 3 and 1 (Fig.  2 a) have a calculated half-life ranging from 0.7 to 1.9 weeks (Additional file  1 : Figure S1M-Q, all p values < 0.02), even though they originate from the same deodorant used by each individual. For some ingredients of deodorant used by volunteer 3 on time 0 (Additional file  1 : Figure S1M, N), a decline was observed during the first week, then little to no traces of these ingredients were detected during weeks 4–6 (T4–T6), then finally these ingredients reappear again during the last 3 weeks of personal product use (T7–T9). This suggests that these ingredients are present exclusively in the personal deodorant used by volunteer 3 before the study. Because a similar deodorant (Additional file  1 : Figure S1O-Q) and a face lotion (Additional file  1 : Figure S1R) was used by volunteer 3 and volunteer 2, respectively, prior to the study, there was no decline or absence of their ingredients during weeks 4–6 (T4–T6).

Polyethylene glycol compounds (Additional file  1 : Figure S1J-L) wash out faster from the skin than polypropylene glycol (Additional file  1 : Figure S1M-Q)(HL ~ 0.5 weeks vs ~ 1.9 weeks) and faster than fatty acids used in lotions (HL ~ 1.2 weeks) (Additional file  1 : Figure S1R), consistent with their hydrophilic (PEG) and hydrophobic properties (PPG and fatty acids) [ 25 , 26 ]. This difference in hydrophobicity is also reflected in the retention time as detected by mass spectrometry. Following the linear decrease of two PPG compounds from T0 to T1, they accumulated noticeably during weeks 2 and 3 (Additional file  1 : Figure S1M, N). This accumulation might be due to other sources of PPG such as the body wash used during this period or the clothes worn by person 3. Although PPG compounds were not listed in the ingredient list of the shampoo, we manually inspected the LC-MS data collected from this product and confirmed the absence of PPG compounds in the shampoo. The data suggest that this trend is characteristic of accumulation of PPG from additional sources. These could be clothes, beds, or sheets, in agreement with the observation of these molecules found in human habitats [ 27 ] but also in the public GNPS mass spectrometry dataset MSV000079274 that investigated the chemicals from dust collected from 1053 mattresses of children.

Temporal molecular and bacterial diversity in response to personal care use

To assess the effect of discontinuing and resuming the use of skin care products on molecular and microbiota dynamics, we first evaluated their temporal diversity. Skin sites varied markedly in their initial level (T0) of molecular and bacterial diversity, with higher molecular diversity at all sites for female participants compared to males (Fig.  3 a, b, Wilcoxon rank-sum-WR test, p values ranging from 0.01 to 0.0001, from foot to arm) and higher bacterial diversity in face (WR test, p  = 0.0009) and armpits (WR test, p  = 0.002) for females (Fig.  3 c, d). Temporal diversity was similar across the right and left sides of each body site of all individuals (WR test, molecular diversity: all p values > 0.05; bacterial diversity: all p values > 0.20). The data show that refraining from using beauty products (T1–T3) leads to a significant decrease in molecular diversity at all sites (Fig.  3 a, b, WR test, face: p  = 8.29e−07, arm: p  = 7.08e−09, armpit: p  = 1.13e−05, foot: p  = 0.002) and bacterial diversity mainly in armpits (WR test, p  = 0.03) and feet (WR test, p  = 0.04) (Fig.  3 c, d). While molecular diversity declined (Fig.  3 a, b) for arms and face, bacterial diversity (Fig.  3 c, d) was less affected in the face and arms when participants did not use skin care products (T1–T3). The molecular diversity remained stable in the arms and face of female participants during common beauty products use (T4–T6) to immediately increase as soon as the volunteers went back to their normal routines (T7–T9) (WR test, p  = 0.006 for the arms and face)(Fig.  3 a, b). A higher molecular (Additional file  1 : Figure S2A) and community (Additional file  1 : Figure S2B) diversity was observed for armpits and feet of all individuals during the use of antiperspirant and foot powder (T4–T6) (WR test, molecular diversity: armpit p  = 8.9e−33, foot p  = 1.03e−11; bacterial diversity: armpit p  = 2.14e−28, foot p  = 1.26e−11), followed by a molecular and bacterial diversity decrease in the armpits when their regular personal beauty product use was resumed (T7–T9) (bacterial diversity: WR test, p  = 4.780e−21, molecular diversity: WR test, p  = 2.159e−21). Overall, our data show that refraining from using beauty products leads to lower molecular and bacterial diversity, while resuming the use increases their diversity. Distinct variations between male and female molecular and community richness were perceived at distinct body parts (Fig.  3 a–d). Although the chemical diversity of personal beauty products does not explain these variations (Additional file  1 : Figure S2C), differences observed between males and females may be attributed to many environmental and lifestyle factors including different original skin care and different frequency of use of beauty products (Additional file  2 : Table S1), washing routines, and diet.

Molecular and bacterial diversity over a 9-week period, comparing samples based on their molecular (UPLC-Q-TOF-MS) or bacterial (16S rRNA amplicon) profiles. Molecular and bacterial diversity using the Shannon index was calculated from samples collected from each body part at each timepoint, separately for female ( n  = 5) and male ( n  = 6) individuals. Error bars represent standard error of the mean calculated at each timepoint, from up to four samples collected from the right and left side of each body part, of females ( n  = 5) and males ( n  = 6) separately. a , b Molecular alpha diversity measured using the Shannon index from five females (left panel) and six males (right panel), over 9 weeks, from four distinct body parts (armpits, face, arms, feet). c , d Bacterial alpha diversity measured using the Shannon index, from skin samples collected from five female (left panel) and six male individuals (right panel), over 9 weeks, from four distinct body parts (armpits, face, arms, feet). See also Additional file  1 : Figure S2

Longitudinal variation of skin metabolomics signatures

To gain insights into temporal metabolomics variation associated with beauty product use, chemical inventories collected over 9 weeks were subjected to multivariate analysis using the widely used Bray–Curtis dissimilarity metric (Fig.  4 a–c, S3A). Throughout the 9-week period, distinct molecular signatures were associated to each specific body site: arm, armpit, face, and foot (Additional file  1 : Figure S3A, Adonis test, p  < 0.001, R 2 0.12391). Mass spectrometric signatures displayed distinct individual trends at each specific body site (arm, armpit, face, and foot) over time, supported by their distinct locations in PCoA (principal coordinate analysis) space (Fig.  4 a, b) and based on the Bray–Curtis distances between molecular profiles (Additional file  1 : Figure S3B, WR test, all p values < 0.0001 from T0 through T9). This suggests a high molecular inter-individual variability over time despite similar changes in personal care routines. Significant differences in molecular patterns associated to ceasing (T1–T3) (Fig.  4 b, Additional file 1 : Figure S3C, WR test, T0 vs T1–T3 p  < 0.001) and resuming the use of common beauty products (T4–T6) (Additional file  1 : Figure S3C) were observed in the arm, face, and foot (Fig.  4 b), although the armpit exhibited the most pronounced changes (Fig.  4 b, Additional file 1 : Figure S3D, E, random forest highlighting that 100% of samples from each phase were correctly predicted). Therefore, we focused our analysis on this region. Molecular changes were noticeable starting the first week (T1) of discontinuing beauty product use. As shown for armpits in Fig.  4 c, these changes at the chemical level are specific to each individual, possibly due to the extremely personalized lifestyles before the study and match their original use of deodorant. Based on the initial use of underarm products (T0) (Additional file  2 : Table S1), two groups of participants can be distinguished: a group of five volunteers who used stick deodorant as evidenced by the mass spectrometry data and another group of volunteers where we found few or no traces suggesting they never or infrequently used stick deodorants (Additional file  2 : Table S1). Based on this criterion, the chemical trends shown in Fig.  4 c highlight that individuals who used stick deodorant before the beginning of the study (volunteers 1, 2, 3, 9, and 12) displayed a more pronounced shift in their armpits’ chemistries as soon as they stopped using deodorant (T1–T3), compared to individuals who had low detectable levels of stick deodorant use (volunteers 4, 6, 7, and 10), or “rarely-to-never” (volunteers 5 and 11) use stick deodorants as confirmed by the volunteers (Additional file  1 : Figure S3F, WR test, T0 vs T1–T3 all p values < 0.0001, with greater distance for the group of volunteers 1, 2, 3, 9, and 12, compared to volunteers 4, 5, 6, 7, 10, and 11). The most drastic shift in chemical profiles was observed during the transition period, when all participants applied the common antiperspirant on a daily basis (T4–T6) (Additional file  1 : Figure S3D, E). Finally, the molecular profiles became gradually more similar to those collected before the experiment (T0) as soon as the participants resumed using their personal beauty products (T7–T9) (Additional file  1 : Figure S3C), although traces of skin care products did last through the entire T7–T9 period in people who do not routinely apply these products (Fig.  4 c).

Individualized influence of beauty product application on skin metabolomics profiles over time. a Multivariate statistical analysis (principal coordinate analysis (PCoA)) comparing mass spectrometry data collected over 9 weeks from the skin of 11 individuals, all body parts, combined (first plot from the left) and then displayed separately (arm, armpits, face, feet). Color scale represents volunteer ID. The PCoA was calculated on all samples together, and subsets of the data are shown in this shared space and the other panels. b The molecular profiles collected over 9 weeks from all body parts, combined then separately (arm, armpits, face, feet). c Representative molecular profiles collected over 9 weeks from armpits of 11 individuals (volunteers 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12). Color gradient in b and c represents timepoints (time 0 to time 9), ranging from the lightest orange color to the darkest one that represent the earliest (time 0) to the latest (time 9) timepoint, respectively. 0.5 timepoints represent additional timepoints where three selected volunteers were samples (volunteers 4, 9, and 10). PCoA plots were generated using the Bray–Curtis dissimilarity matrix and visualized in Emperor [ 28 ]. See also Additional file  1 : Figure S3

Comparing chemistries detected in armpits at the end timepoints—when no products were used (T3) and during product use (T6)—revealed distinct molecular signatures characteristic of each phase (random forest highlighting that 100% of samples from each group were correctly predicted, see Additional file  1 : Figure S3D, E). Because volunteers used the same antiperspirant during T4–T6, molecular profiles converged during that time despite individual patterns at T3 (Fig.  4 b, c, Additional file  1 : Figure S3D). These distinct chemical patterns reflect the significant impact of beauty products on skin molecular composition. Although these differences may in part be driven by beauty product ingredients detected on the skin (Additional file  1 : Figure S1), we anticipated that additional host- and microbe-derived molecules may also be involved in these molecular changes.

To characterize the chemistries that vary over time, we used molecular networking, a MS visualization approach that evaluates the relationship between MS/MS spectra and compares them to reference MS/MS spectral libraries of known compounds [ 29 , 30 ]. We recently showed that molecular networking can successfully organize large-scale mass spectrometry data collected from the human skin surface [ 18 , 19 ]. Briefly, molecular networking uses the MScluster algorithm [ 31 ] to merge all identical spectra and then compares and aligns all unique pairs of MS/MS spectra based on their similarities where 1.0 indicates a perfect match. Similarities between MS/MS spectra are calculated using a similarity score, and are interpreted as molecular families [ 19 , 24 , 32 , 33 , 34 ]. Here, we used this method to compare and characterize chemistries found in armpits, arms, face, and foot of 11 participants. Based on MS/MS spectral similarities, chemistries highlighted through molecular networking (Additional file  1 : Figure S4A) were associated with each body region with 8% of spectra found exclusively in the arms, 12% in the face, 14% in the armpits, and 2% in the foot, while 18% of the nodes were shared between all four body parts and the rest of spectra were shared between two body sites or more (Additional file  1 : Figure S4B). Greater spectral similarities were highlighted between armpits, face, and arm (12%) followed by the arm and face (9%) (Additional file  1 : Figure S4B).

Molecules were annotated with Global Natural Products Social Molecular Networking (GNPS) libraries [ 29 ], using accurate parent mass and MS/MS fragmentation patterns, according to level 2 or 3 of annotation defined by the 2007 metabolomics standards initiative [ 35 ]. Through annotations, molecular networking revealed that many compounds derived from steroids (Fig.  5 a–d), bile acids (Additional file  1 : Figure S5A-D), and acylcarnitines (Additional file  1 : Figure S5E-F) were exclusively detected in the armpits. Using authentic standards, the identity of some pheromones and bile acids were validated to a level 1 identification with matched retention times (Additional file  1 : Figure S6B, S7A, C, D). Other steroids and bile acids were either annotated using standards with identical MS/MS spectra but slightly different retention times (Additional file  1 : Figure S6A) or annotated with MS/MS spectra match with reference MS/MS library spectra (Additional file  1 : Figure S6C, D, S7B, S6E-G). These compounds were therefore classified as level 3 [ 35 ]. Acylcarnitines were annotated to a family of possible acylcarnitines (we therefore classify as level 3), as the positions of double bonds or cis vs trans configurations are unknown (Additional file  1 : Figure S8A, B).

Underarm steroids and their longitudinal abundance. a – d Steroid molecular families in the armpits and their relative abundance over a 9-week period. Molecular networking was applied to characterize chemistries from the skin of 11 healthy individuals. The full network is shown in Additional file  1 : Figure S4A, and networking parameters can be found here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=284fc383e4c44c4db48912f01905f9c5 for MS/MS datasets MSV000081582. Each node represents a consensus of a minimum of 3 identical MS/MS spectra. Yellow nodes represent MS/MS spectra detected in armpits samples. Hexagonal shape represents MS/MS spectra match between skin samples and chemical standards. Plots are representative of the relative abundance of each compound over time, calculated separately from LC-MS1 data collected from the armpits of each individual. Steroids detected in armpits are a , dehydroisoandrosterone sulfate ( m/z 369.190, rt 247 s), b androsterone sulfate ( m/z 371.189, rt 261 s), c 1-dehydroandrostenedione ( m/z 285.185, rt 273 s), and d dehydroandrosterone ( m/z 289.216, rt 303 s). Relative abundance over time of each steroid compound is represented. Error bars represent the standard error of the mean calculated at each timepoint from four armpit samples from the right and left side of each individual separately. See also Additional file  1 : Figures S4-S8

Among the steroid compounds, several molecular families were characterized: androsterone (Fig.  5 a, b, d), androstadienedione (Fig.  5 c), androstanedione (Additional file  1 : Figure S6E), androstanolone (Additional file  1 : Figure S6F), and androstenedione (Additional file  1 : Figure S6G). While some steroids were detected in the armpits of several individuals, such as dehydroisoandrosterone sulfate ( m/z 369.19, rt 247 s) (9 individuals) (Fig.  5 a, Additional file  1 : Figure S6A), androsterone sulfate ( m/z 371.189, rt 261 s) (9 individuals) (Fig.  5 b, Additional file  1 : Figure S6C), and 5-alpha-androstane-3,17-dione ( m/z 271.205, rt 249 s) (9 individuals) (Additional file  1 : Figure S6E), other steroids including 1-dehydroandrostenedione ( m/z 285.185, rt 273 s) (Fig.  5 c, Additional file  1 : Figure S6B), dehydroandrosterone ( m/z 289.216, rt 303 s) (Fig.  5 d, Additional file 1 : Figure S6D), and 5-alpha-androstan-17.beta-ol-3-one ( m/z 291.231, rt 318 s) (Additional file  1 : Figure S6F) were only found in the armpits of volunteer 11 and 4-androstene-3,17-dione ( m/z 287.200, rt 293 s) in the armpits of volunteer 11 and volunteer 5, both are male that never applied stick deodorants (Additional file  1 : Figure S6G). Each molecular species exhibited a unique pattern over the 9-week period. The abundance of dehydroisoandrosterone sulfate (Fig.  5 a, WR test, p  < 0.01 for 7 individuals) and dehydroandrosterone (Fig.  5 a, WR test, p  = 0.00025) significantly increased during the use of antiperspirant (T4–T6), while androsterone sulfate (Fig.  5 b) and 5-alpha-androstane-3,17-dione (Additional file  1 : Figure S6E) display little variation over time. Unlike dehydroisoandrosterone sulfate (Fig.  5 a) and dehydroandrosterone (Fig.  5 d), steroids including 1-dehydroandrostenedione (Fig.  5 c, WR test, p  = 0.00024) and 4-androstene-3,17-dione (Additional file  1 : Figure S6G, WR test, p  = 0.00012) decreased in abundance during the 3 weeks of antiperspirant application (T4–T6) in armpits of male 11, and their abundance increased again when resuming the use of his normal skin care routines (T7–T9). Interestingly, even within the same individual 11, steroids were differently impacted by antiperspirant use as seen for 1-dehydroandrostenedione that decreased in abundance during T4–T6 (Fig.  5 c, WR test, p  = 0.00024), while dehydroandrosterone increased in abundance (Fig.  5 d, WR test, p  = 0.00025), and this increase was maintained during the last 3 weeks of the study (T7–T9).

In addition to steroids, many bile acids (Additional file  1 : Figure S5A-D) and acylcarnitines (Additional file  1 : Figure S5E-F) were detected on the skin of several individuals through the 9-week period. Unlike taurocholic acid found only on the face (Additional file  1 : Figures S5A, S7A) and tauroursodeoxycholic acid detected in both armpits and arm samples (Additional file  1 : Figures S5B, S7B), other primary bile acids such as glycocholic (Additional file  1 : Figures S5C, S7C) and chenodeoxyglycocholic acid (Additional file  1 : Figures S5D, S7D) were exclusively detected in the armpits. Similarly, acylcarnitines were also found either exclusively in the armpits (hexadecanoyl carnitines) (Additional file  1 : Figures S5E, S8A) or in the armpits and face (tetradecenoyl carnitine) (Additional file  1 : Figures S5F, S8B) and, just like the bile acids, they were also stably detected during the whole 9-week period.

Bacterial communities and their variation over time

Having demonstrated the impact of beauty products on the chemical makeup of the skin, we next tested the extent to which skin microbes are affected by personal care products. We assessed temporal variation of bacterial communities detected on the skin of healthy individuals by evaluating dissimilarities of bacterial collections over time using unweighted UniFrac distance [ 36 ] and community variation at each body site in association to beauty product use [ 3 , 15 , 37 ]. Unweighted metrics are used for beta diversity calculations because we are primarily concerned with changes in community membership rather than relative abundance. The reason for this is that skin microbiomes can fluctuate dramatically in relative abundance on shorter timescales than that assessed here. Longitudinal variations were revealed for the armpits (Fig.  6 a) and feet microbiome by their overall trend in the PCoA plots (Fig.  6 b), while the arm (Fig.  6 c) and face (Fig.  6 d) displayed relatively stable bacterial profiles over time. As shown in Fig.  6 a–d, although the microbiome was site-specific, it varied more between individuals and this inter-individual variability was maintained over time despite same changes in personal care routine (WR test, all p values at all timepoints < 0.05, T5 p  = 0.07), in agreement with previous findings that individual differences in the microbiome are large and stable over time [ 3 , 4 , 10 , 37 ]. However, we show that shifts in the microbiome can be induced by changing hygiene routine and therefore skin chemistry. Changes associated with using beauty products (T4–T6) were more pronounced for the armpits (Fig.  6 a, WR test, p  = 1.61e−52) and feet (Fig.  6 b, WR test, p  = 6.15e−09), while little variations were observed for the face (Fig.  6 d, WR test, p  = 1.402.e−83) and none for the arms (Fig.  6 c, WR test, p  = 0.296).

Longitudinal variation of skin bacterial communities in association with beauty product use. a - d Bacterial profiles collected from skin samples of 11 individuals, over 9 weeks, from four distinct body parts a) armpits, b) feet, c) arms and d) face, using multivariate statistical analysis (Principal Coordinates Analysis PCoA) and unweighted Unifrac metric. Each color represents bacterial samples collected from an individual. PCoA were calculated separately for each body part. e , f Representative Gram-negative (Gram -) bacteria collected from arms, armpits, face and feet of e) female and f) male participants. See also Additional file  1 : Figure S9A, B showing Gram-negative bacterial communities represented at the genus level

A significant increase in abundance of Gram-negative bacteria including the phyla Proteobacteria and Bacteroidetes was noticeable for the armpits and feet of both females (Fig.  6 e; Mann–Whitney U , p  = 8.458e−07) and males (Fig.  6 f; Mann–Whitney U , p  = 0.0004) during the use of antiperspirant (T4–T6), while their abundance remained stable for the arms and face during that time (Fig.  6 e, f; female arm p  = 0.231; female face p value = 0.475; male arm p = 0.523;male face p  = 6.848751e−07). These Gram-negative bacteria include Acinetobacter and Paracoccus genera that increased in abundance in both armpits and feet of females (Additional file  1 : Figure S9A), while a decrease in abundance of Enhydrobacter was observed in the armpits of males (Additional file  1 : Figure S9B). Cyanobacteria, potentially originating from plant material (Additional file  1 : Figure S9C) also increased during beauty product use (T4–T6) especially in males, in the armpits and face of females (Fig.  6 e) and males (Fig.  6 f). Interestingly, although chloroplast sequences (which group phylogenetically within the cyanobacteria [ 38 ]) were only found in the facial cream (Additional file  1 : Figure S9D), they were detected in other locations as well (Fig.  6 e, f. S9E, F), highlighting that the application of a product in one region will likely affect other regions of the body. For example, when showering, a face lotion will drip down along the body and may be detected on the feet. Indeed, not only did the plant material from the cream reveal this but also the shampoo used for the study for which molecular signatures were readily detected on the feet as well (Additional file  1 : Figure S10A). Minimal average changes were observed for Gram-positive organisms (Additional file  1 : Figure S10B, C), although in some individuals the variation was greater than others (Additional file  1 : Figure S10D, E) as discussed for specific Gram-positive taxa below.

At T0, the armpit’s microflora was dominated by Staphylococcus (26.24%, 25.11% of sequencing reads for females and 27.36% for males) and Corynebacterium genera (26.06%, 17.89% for females and 34.22% for males) (Fig.  7 a—first plot from left and Additional file  1 : Figure S10D, E). They are generally known as the dominant armpit microbiota and make up to 80% of the armpit microbiome [ 39 , 40 ]. When no deodorants were used (T1–T3), an overall increase in relative abundance of Staphylococcus (37.71%, 46.78% for females and 30.47% for males) and Corynebacterium (31.88%, 16.50% for females and 44.15% for males) genera was noticeable (WR test, p  < 3.071e−05) (Fig.  7 a—first plot from left), while the genera Anaerococcus and Peptoniphilus decreased in relative abundance (WR test, p  < 0.03644) (Fig.  7 a—first plot from left and Additional file  1 : Figure S10D, E). When volunteers started using antiperspirants (T4–T6), the relative abundance of Staphylococcus (37.71%, 46.78% females and 30.47% males, to 21.71%, 25.02% females and 19.25% males) and Corynebacterium (31.88%, 16.50% females and 44.15% males, to 15.83%, 10.76% females and 19.60% males) decreased (WR test, p  < 3.071e−05) (Fig.  7 a, Additional file  1 : Figure S10D, E) and at the same time, the overall alpha diversity increased significantly (WR test, p  = 3.47e−11) (Fig.  3 c, d). The microbiota Anaerococcus (WR test, p  = 0.0006018) , Peptoniphilus (WR test, p  = 0.008639), and Micrococcus (WR test, p  = 0.0377) increased significantly in relative abundance, together with a lot of additional low-abundant species that lead to an increase in Shannon alpha diversity (Fig.  3 c, d). When participants went back to normal personal care products (T7–T9), the underarm microbiome resembled the original underarm community of T0 (WR test, p  = 0.7274) (Fig.  7 a). Because armpit bacterial communities are person-specific (inter-individual variability: WR test, all p values at all timepoints < 0.05, besides T5 p n.s), variation in bacterial abundance upon antiperspirant use (T4–T6) differ between individuals and during the whole 9-week period (Fig.  7a —taxonomic plots per individual). For example, the underarm microbiome of male 5 exhibited a unique pattern, where Corynebacterium abundance decreased drastically during the use of antiperspirant (82.74 to 11.71%, WR test, p  = 3.518e−05) while in the armpits of female 9 a huge decrease in Staphylococcus abundance was observed (Fig.  7 a) (65.19 to 14.85%, WR test, p  = 0.000113). Unlike other participants, during T0–T3, the armpits of individual 11 were uniquely characterized by the dominance of a sequence that matched most closely to the Enhydrobacter genera . The transition to antiperspirant use (T4–T6) induces the absence of Enhydrobacter (30.77 to 0.48%, WR test, p  = 0.01528) along with an increase of Corynebacterium abundance (26.87 to 49.74%, WR test, p  = 0.1123) (Fig.  7 a—male 11).

Person-to-person bacterial variabilities over time in the armpits and feet. a Armpit microbiome changes when stopping personal care product use, then resuming. Armpit bacterial composition of the 11 volunteers combined, then separately, (female 1, female 2, female 3, male 4, male 5, male 6, male 7, female 9, male 10, male 11, female 12) according to the four periods within the experiment. b Feet bacterial variation over time of the 12 volunteers combined, then separately (female 1, female 2, female 3, male 4, male 5, male 6, male 7, female 9, male 10, male 11, female 12) according to the four periods within the experiment. See also Additional file  1 : Figure S9-S13

In addition to the armpits, a decline in abundance of Staphylococcus and Corynebacterium was perceived during the use of the foot powder (46.93% and 17.36%, respectively) compared to when no beauty product was used (58.35% and 22.99%, respectively) (WR test, p  = 9.653e−06 and p  = 0.02032, respectively), while the abundance of low-abundant foot bacteria significantly increased such as Micrococcus (WR test, p  = 1.552e−08), Anaerococcus (WR test, p  = 3.522e−13), Streptococcus (WR test, p  = 1.463e−06), Brevibacterium (WR test, p  = 6.561e−05), Moraxellaceae (WR test, p  = 0.0006719), and Acinetobacter (WR test, p  = 0.001487), leading to a greater bacterial diversity compared to other phases of the study (Fig.  7 b first plot from left, Additional file  1 : Figure S10D, E, Fig.  3 c, d).

We further evaluated the relationship between the two omics datasets by superimposing the principal coordinates calculated from metabolome and microbiome data (Procrustes analysis) (Additional file  1 : Figure S11) [ 34 , 41 , 42 ]. Metabolomics data were more correlated with patterns observed in microbiome data in individual 3 (Additional file  1 : Figure S11C, Mantel test, r  = 0.23, p  < 0.001), individual 5 (Additional file  1 : Figure S11E, r  = 0.42, p  < 0.001), individual 9 (Additional file  1 : Figure S11H, r  = 0.24, p  < 0.001), individual 10 (Additional file  1 : Figure S11I, r  = 0.38, p  < 0.001), and individual 11 (Additional file  1 : Figure S11J, r  = 0.35, p  < 0.001) when compared to other individuals 1, 2, 4, 6, 7, and 12 (Additional file  1 : Figure S11A, B, D, F, G, K, respectively) (Mantel test, all r  < 0.2, all p values < 0.002, for volunteer 2 p n.s). Furthermore, these correlations were individually affected by ceasing (T1–T3) or resuming the use of beauty products (T4–T6 and T7–T9) (Additional file  1 : Figure S11A-K).

Overall, metabolomics–microbiome correlations were consistent over time for the arms, face, and feet although alterations were observed in the arms of volunteers 7 (Additional file  1 : Figure S11G) and 10 (Additional file  1 : Figure S11I) and the face of volunteer 7 (Additional file  1 : Figure S11G) during product use (T4–T6). Molecular–bacterial correlations were mostly affected in the armpits during antiperspirant use (T4–T6), as seen for volunteers male 7 (Additional file  1 : Figure S11G) and 11 (Additional file  1 : Figure S11J) and females 2 (Additional file  1 : Figure S11B), 9 (Additional file  1 : Figure S11H), and 12 (Additional file  1 : Figure S11K). This perturbation either persisted during the last 3 weeks (Additional file  1 : Figure S11D, E, H, I, K) when individuals went back to their normal routine (T7–T9) or resembled the initial molecular–microbial correlation observed in T0 (Additional file  1 : Figure S11C, G, J). These alterations in molecular–bacterial correlation are driven by metabolomics changes during antiperspirant use as revealed by metabolomics shifts on the PCoA space (Additional file  1 : Figure S11), partially due to the deodorant’s chemicals (Additional file  1 : Figure S1J, K) but also to changes observed in steroid levels in the armpits (Fig.  5A, C, D , Additional file 1 : Figure S6G), suggesting metabolome-dependant changes of the skin microbiome. In agreement with previous findings that showed efficient biotransformation of steroids by Corynebacterium [ 43 , 44 ], our correlation analysis associates specific steroids that were affected by antiperspirant use in the armpits of volunteer 11 (Fig.  5 c, d, Additional file 1 : Figure S6G) with microbes that may produce or process them: 1-dehydroandrostenedione, androstenedione, and dehydrosterone with Corynebacterium ( r  = − 0.674, p  = 6e−05; r  = 0.671, p  = 7e−05; r  = 0.834, p  < 1e−05, respectively) (Additional file  1 : Figure S12A, B, C, respectively) and Enhydrobacter ( r  = 0.683, p  = 4e−05; r  = 0.581, p  = 0.00095; r  = 0.755, p  < 1e−05 respectively) (Additional file  1 : Figure S12D, E, F, respectively).

Despite the widespread use of skin care and hygiene products, their impact on the molecular and microbial composition of the skin is poorly studied. We established a workflow that examines individuals to systematically study the impact of such lifestyle characteristics on the skin by taking a broad look at temporal molecular and bacterial inventories and linking them to personal skin care product use. Our study reveals that when the hygiene routine is modified, the skin metabolome and microbiome can be altered, but that this alteration depends on product use and location on the body. We also show that like gut microbiome responses to dietary changes [ 20 , 21 ], the responses are individual-specific.

We recently reported that traces of our lifestyle molecules can be detected on the skin days and months after the original application [ 18 , 19 ]. Here, we show that many of the molecules associated with our personal skin and hygiene products had a half-life of 0.5 to 1.9 weeks even though the volunteers regularly showered, swam, or spent time in the ocean. Thus, a single application of some of these products has the potential to alter the microbiome and skin chemistry for extensive periods of time. Our data suggests that although host genetics and diet may play a role, a significant part of the resilience of the microbiome that has been reported [ 10 , 45 ] is due to the resilience of the skin chemistry associated with personal skin and hygiene routines, or perhaps even continuous re-exposure to chemicals from our personal care routines that are found on mattresses, furniture, and other personal objects [ 19 , 27 , 46 ] that are in constant contact. Consistent with this observation is that individuals in tribal regions and remote villages that are infrequently exposed to the types of products used in this study have very different skin microbial communities [ 47 , 48 ] and that the individuals in this study who rarely apply personal care products had a different starting metabolome. We observed that both the microbiome and skin chemistry of these individuals were most significantly affected by these products. This effect by the use of products at T4–T6 on the volunteers that infrequently used them lasted to the end phase of the study even though they went back to infrequent use of personal care products. What was notable and opposite to what the authors originally hypothesized is that the use of the foot powder and antiperspirant increased the diversity of microbes and that some of this diversity continued in the T7–T9 phase when people went back to their normal skin and hygiene routines. It is likely that this is due to the alteration in the nutrient availability such as fatty acids and moisture requirements, or alteration of microbes that control the colonization via secreted small molecules, including antibiotics made by microbes commonly found on the skin [ 49 , 50 ].

We detected specific molecules on the skin that originated from personal care products or from the host. One ingredient that lasts on the skin is propylene glycol, which is commonly used in deodorants and antiperspirants and added in relatively large amounts as a humectant to create a soft and sleek consistency [ 51 ]. As shown, daily use of personal care products is leading to high levels of exposure to these polymers. Such polymers cause contact dermatitis in a subset of the population [ 51 , 52 ]. Our data reveal a lasting accumulation of these compounds on the skin, suggesting that it may be possible to reduce their dose in deodorants or frequency of application and consequently decrease the degree of exposure to such compounds. Formulation design of personal care products may be influenced by performing detailed outcome studies. In addition, longer term impact studies are needed, perhaps in multiple year follow-up studies, to assess if the changes we observed are permanent or if they will recover to the original state.

Some of the host- and microbiome-modified molecules were also detected consistently, such as acylcarnitines, bile acids, and certain steroids. This means that a portion of the molecular composition of a person’s skin is not influenced by the beauty products applied to the skin, perhaps reflecting the level of exercise for acylcarnitines [ 53 , 54 ] or the liver (dominant location where they are made) or gallbladder (where they are stored) function for bile acids. The bile acid levels are not related to sex and do not change in amount during the course of this study. While bile acids are typically associated with the human gut microbiome [ 34 , 55 , 56 , 57 , 58 ], it is unclear what their role is on the skin and how they get there. One hypothesis is that they are present in the sweat that is excreted through the skin, as this is the case for several food-derived molecules such as caffeine or drugs and medications that have been previously reported on the human skin [ 19 ] or that microbes synthesize them de novo [ 55 ]. The only reports we could find on bile acids being associated with the skin describe cholestasis and pruritus diseases. Cholestasis and pruritus in hepatobiliary disease have symptoms of skin bile acid accumulation that are thought to be responsible for severe skin itching [ 59 , 60 ]. However, since bile acids were found in over 50% of the healthy volunteers, their detection on the skin is likely a common phenotype among the general population and not only reflective of disease, consistent with recent reports challenging these molecules as biomarkers of disease [ 59 ]. Other molecules that were detected consistently came from personal care products.

Aside from molecules that are person-specific and those that do not vary, there are others that can be modified via personal care routines. Most striking is how the personal care routines influenced changes in hormones and pheromones in a personalized manner. This suggests that there may be personalized recipes that make it possible to make someone more or less attractive to others via adjustments of hormonal and pheromonal levels through alterations in skin care.

Here, we describe the utilization of an approach that combines metabolomics and microbiome analysis to assess the effect of modifying personal care regime on skin chemistry and microbes. The key findings are as follows: (1) Compounds from beauty products last on the skin for weeks after their first use despite daily showering. (2) Beauty products alter molecular and bacterial diversity as well as the dynamic and structure of molecules and bacteria on the skin. (3) Molecular and bacterial temporal variability is product-, site-, and person-specific, and changes are observed starting the first week of beauty product use. This study provides a framework for future investigations to understand how lifestyle characteristics such as diet, outdoor activities, exercise, and medications shape the molecular and microbial composition of the skin. These factors have been studied far more in their impact on the gut microbiome and chemistry than in the skin. Revealing how such factors can affect skin microbes and their associated metabolites may be essential to define long-term skin health by restoring the appropriate microbes particularly in the context of skin aging [ 61 ] and skin diseases [ 49 ] as has shown to be necessary for amphibian health [ 62 , 63 ], or perhaps even create a precision skin care approach that utilizes the proper care ingredients based on the microbial and chemical signatures that could act as key players in host defense [ 49 , 64 , 65 ].

Subject recruitment and sample collection

Twelve individuals between 25 and 40 years old were recruited to participate in this study, six females and six males. Female volunteer 8 dropped out of the study as she developed a skin irritation during the T1–T3 phase. All volunteers signed a written informed consent in accordance with the sampling procedure approved by the UCSD Institutional Review Board (Approval Number 161730). Volunteers were required to follow specific instructions during 9 weeks. They were asked to bring in samples of their personal care products they used prior to T0 so they could be sampled as well. Following the initial timepoint time 0 and during the first 3 weeks (week 1–week 3), volunteers were asked not to use any beauty products (Fig.  1 b). During the next 3 weeks (week 4–week 6), four selected commercial beauty products provided to all volunteers were applied once a day at specific body part (deodorant for the armpits, soothing foot powder between the toes, sunscreen for the face, and moisturizer for front forearms) (Fig.  1 b, Additional file  3 : Table S2 Ingredient list of beauty products). During the first 6 weeks, volunteers were asked to shower with a head to toe shampoo. During the last 3 weeks (week 7–week 9), all volunteers went back to their normal routine and used the personal care products used before the beginning of the study (Fig.  1 b). Volunteers were asked not to shower the day before sampling. Samples were collected by the same three researchers to ensure consistency in sampling and the area sampled. Researchers examined every subject together and collected metabolomics and microbiome samples from each location together. Samples were collected once a week (from day 0 to day 68—10 timepoints total) for volunteers 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, and 12, and on day 0 and day 6 for volunteer 8. For individuals 4, 9, and 10, samples were collected twice a week. Samples collected for 11 volunteers during 10 timepoints: 11 volunteers × 10 timepoints × 4 samples × 4 body sites = 1760. Samples collected from 3 selected volunteers during 9 additional timepoints: 3 volunteers × 9 timepoints × 4 samples × 4 body sites = 432. All samples were collected following the same protocol described in [ 18 ]. Briefly, samples were collected over an area of 2 × 2 cm, using pre-moistened swabs in 50:50 ethanol/water solution for metabolomics analysis or in Tris-EDTA buffer for 16S rRNA sequencing. Four samples were collected from each body part right and left side. The locations sampled were the face—upper cheek bone and lower jaw, armpit—upper and lower area, arm—front of the elbow (antecubitis) and forearm (antebrachium), and feet—in between the first and second toe and third and fourth toe. Including personal care product references, a total of 2275 samples were collected over 9 weeks and were submitted to both metabolomics and microbial inventories.

Metabolite extraction and UPLC-Q-TOF mass spectrometry analysis

Skin swabs were extracted and analyzed using a previously validated workflow described in [ 18 , 19 ]. All samples were extracted in 200 μl of 50:50 ethanol/water solution for 2 h on ice then overnight at − 20 °C. Swab sample extractions were dried down in a centrifugal evaporator then resuspended by vortexing and sonication in a 100 μl 50:50 ethanol/water solution containing two internal standards (fluconazole 1 μM and amitriptyline 1 μM). The ethanol/water extracts were then analyzed using a previously validated UPLC-MS/MS method [ 18 , 19 ]. We used a ThermoScientific UltiMate 3000 UPLC system for liquid chromatography and a Maxis Q-TOF (Quadrupole-Time-of-Flight) mass spectrometer (Bruker Daltonics), controlled by the Otof Control and Hystar software packages (Bruker Daltonics) and equipped with ESI source. UPLC conditions of analysis are 1.7 μm C18 (50 × 2.1 mm) UHPLC Column (Phenomenex), column temperature 40 °C, flow rate 0.5 ml/min, mobile phase A 98% water/2% acetonitrile/0.1% formic acid ( v / v ), mobile phase B 98% acetonitrile/2% water/0.1% formic acid ( v / v ). A linear gradient was used for the chromatographic separation: 0–2 min 0–20% B, 2–8 min 20–99% B, 8–9 min 99–99% B, 9–10 min 0% B. Full-scan MS spectra ( m/z 80–2000) were acquired in a data-dependant positive ion mode. Instrument parameters were set as follows: nebulizer gas (nitrogen) pressure 2 Bar, capillary voltage 4500 V, ion source temperature 180 °C, dry gas flow 9 l/min, and spectra rate acquisition 10 spectra/s. MS/MS fragmentation of 10 most intense selected ions per spectrum was performed using ramped collision induced dissociation energy, ranged from 10 to 50 eV to get diverse fragmentation patterns. MS/MS active exclusion was set after 4 spectra and released after 30 s.

Mass spectrometry data collected from the skin of 12 individuals can be found here MSV000081582.

LC-MS data processing

LC-MS raw data files were converted to mzXML format using Compass Data analysis software (Bruker Daltonics). MS1 features were selected for all LC-MS datasets collected from the skin of 12 individuals and blank samples (total 2275) using the open-source software MZmine [ 66 ]—see Additional file  4 : Table S3 for parameters. Subsequent blank filtering, total ion current, and internal standard normalization were performed (Additional file  5 : Table S4) for representation of relative abundance of molecular features (Fig.  2 , Additional file  1 : Figure S1), principal coordinate analysis (PCoA) (Fig.  4 ). For steroid compounds in Fig.  5 a–d, bile acids (Additional file  1 : Figure S5A-D), and acylcarnitines (Additional file  1 : Figure S5E, F) compounds, crop filtering feature available in MZmine [ 66 ] was used to identify each feature separately in all LC-MS data collected from the skin of 12 individuals (see Additional file  4 : Table S3 for crop filtering parameters and feature finding in Additional file  6 : Table S5).

Heatmap in Fig.  2 was constructed from the bucket table generated from LC-MS1 features (Additional file  7 : Table S6) and associated metadata (Additional file  8 : Table S7) using the Calour command line available here: https://github.com/biocore/calour . Calour parameters were as follows: normalized read per sample 5000 and cluster feature minimum reads 50. Procrustes and Pearson correlation analyses in Additional file  1 : Figures S10 and S11 were performed using the feature table in Additional file  9 : Table S8, normalized using the probabilistic quotient normalization method [ 67 ].

16S rRNA amplicon sequencing

16S rRNA sequencing was performed following the Earth Microbiome Project protocols [ 68 , 69 ], as described before [ 18 ]. Briefly, DNA was extracted using MoBio PowerMag Soil DNA Isolation Kit and the V4 region of the 16S rRNA gene was amplified using barcoded primers [ 70 ]. PCR was performed in triplicate for each sample, and V4 paired-end sequencing [ 70 ] was performed using Illumina HiSeq (La Jolla, CA). Raw sequence reads were demultiplexed and quality controlled using the defaults, as provided by QIIME 1.9.1 [ 71 ]. The primary OTU table was generated using Qiita ( https://qiita.ucsd.edu/ ), using UCLUST ( https://academic.oup.com/bioinformatics/article/26/19/2460/230188 ) closed-reference OTU picking method against GreenGenes 13.5 database [ 72 ]. Sequences can be found in EBI under accession number EBI: ERP104625 or in Qiita ( qiita.ucsd.edu ) under Study ID 10370. Resulting OTU tables were then rarefied to 10,000 sequences/sample for downstream analyses (Additional file  10 Table S9). See Additional file  11 : Table S10 for read count per sample and Additional file  1 : Figure S13 representing the samples that fall out with rarefaction at 10,000 threshold. The dataset includes 35 blank swab controls and 699 empty controls. The blank samples can be accessed through Qiita ( qiita.ucsd.edu ) as study ID 10370 and in EBI with accession number EBI: ERP104625. Blank samples can be found under the metadata category “sample_type” with the name “empty control” and “Swabblank.” These samples fell below the rarefaction threshold at 10,000 (Additional file  11 : Table S10).

To rule out the possibility that personal care products themselves contained the microbes that induced the changes in the armpit and foot microbiomes that were observed in this study (Fig.  7 ), we subjected the common personal care products that were used in this study during T4–T6 also to 16S rRNA sequencing. The data revealed that within the limit of detectability of the current experiment, few 16S signatures were detected. One notable exception was the most dominant plant-originated bacteria chloroplast detected in the sunscreen lotion applied on the face (Additional file  1 : Figure S9D), that was also detected on the face of individuals and at a lower level on their arms, sites where stable microbial communities were observed over time (Additional file  1 : Figure S9E, F). This finding is in agreement with our previous data from the 3D cartographical skin maps that revealed the presence of co-localized chloroplast and lotion molecules [ 18 ]. Other low-abundant microbial signatures found in the sunscreen lotion include additional plant-associated bacteria: mitochondria [ 73 ], Bacillaceae [ 74 , 75 ], Planococcaceae [ 76 ], and Ruminococcaceae family [ 77 ], but all these bacteria are not responsible for microbial changes associated to beauty product use, as they were poorly detected in the armpits and feet (Fig.  7 ).

To assess the origin of Cyanobacteria detected in skin samples, each Greengenes [ 72 ] 13_8 97% OTU table (per lane; obtained from Qiita [ 78 ] study 10,370) was filtered to only features with a p__Cyanobacteria phylum. The OTU maps for these tables—which relate each raw sequence to an OTU ID—were then filtered to only those observed p__Cyanobacteria OTU IDs. The filtered OTU map was used to extract the raw sequences into a single file. Separately, the unaligned Greengenes 13_8 99% representative sequences were filtered into two sets, first the set of representatives associated with c__Chloroplast (our interest database), and second the set of sequences associated with p__Cyanobacteria without the c__Chloroplast sequences (our background database). Platypus Conquistador [ 79 ] was then used to determine what reads were observed exclusively in the interest database and not in the background database. Of the 4,926,465 raw sequences associated with a p__Cyanobacteria classification (out of 318,686,615 total sequences), at the 95% sequence identity level with 100% alignment, 4,860,258 sequences exclusively recruit to full-length chloroplast 16S by BLAST [ 80 ] with the bulk recruiting to streptophytes (with Chlorophyta and Stramenopiles to a lesser extent). These sequences do not recruit non-chloroplast Cyanobacteria full length 16S.

Half-life calculation for metabolomics data

In order to estimate the biological half-life of molecules detected in the skin, the first four timepoints of the study (T0, T1, T2, T3) were considered for the calculation to allow the monitoring of personal beauty products used at T0. The IUPAC’s definition of biological half-life as the time required to a substance in a biological system to be reduced to half of its value, assuming an approximately exponential removal [ 81 ] was used. The exponential removal can be described as C ( t )  =  C 0 e − tλ where t represents the time in weeks, C 0 represents the initial concentration of the molecule, C ( t ) represents the concentration of the molecule at time t , and λ is the rate of removal [ http://onlinelibrary.wiley.com/doi/10.1002/9780470140451.ch2/summary ]. The parameter λ was estimated by a mixed linear effects model in order to account for the paired sample structure. The regression model tests the null hypothesis that λ is equal to zero and only the significant ( p value < 0.05) parameters were considered.

Principal coordinate analysis

We performed principal coordinate analysis (PCoA) on both metabolomics and microbiome data. For metabolomics, we used MS1 features (Additional file  5 : Table S4) and calculated Bray–Curtis dissimilarity metric using ClusterApp ( https://github.com/mwang87/q2_metabolomics ).

For microbiome data, we used rarefied OTU table (Additional file 10 : Table S9) and used unweighted UniFrac metric [ 36 ] to calculate beta diversity distance matrix using QIIME2 (https://qiime2.org). Results from both data sources were visualized using Emperor ( https://biocore.github.io/emperor/ ) [ 28 ].

Molecular networking

Molecular networking was generated from LC-MS/MS data collected from skin samples of 11 individuals MSV000081582, using the Global Natural Products Social Molecular Networking platform (GNPS) [ 29 ]. Molecular network parameters for MS/MS data collected from all body parts of 11 individuals during T0–T9 MSV000081582 are accessible here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=284fc383e4c44c4db48912f01905f9c5 . Molecular network parameters for MS/MS data collected from armpits T0–T3 MSV000081582 and deodorant used by individual 1 and 3 MSV000081580 can be found here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=f5325c3b278a46b29e8860ec57915ad and here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=aaa1af68099d4c1a87e9a09f398fe253 , respectively. Molecular networks were exported and visualized in Cytoscape 3.4.0. [ 82 ]. Molecular networking parameters were set as follows: parent mass tolerance 1 Da, MS/MS fragment ion tolerance 0.5 Da, and cosine threshold 0.65 or greater, and only MS/MS spectral pairs with at least 4 matched fragment ions were included. Each MS/MS spectrum was only allowed to connect to its top 10 scoring matches, resulting in a maximum of 10 connections per node. The maximum size of connected components allowed in the network was 600, and the minimum number of spectra required in a cluster was 3. Venn diagrams were generated from Cytoscape data http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=284fc383e4c44c4db48912f01905f9c5 using Cytoscape [ 82 ] Venn diagram app available here http://apps.cytoscape.org/apps/all .

Shannon molecular and bacterial diversity

The diversity analysis was performed separately for 16S rRNA data and LC-MS data. For each sample in each feature table (LC-MS data and microbiome data), we calculated the value of the Shannon diversity index. For LC-MS data, we used the full MZmine feature table (Additional file  5 : Table S4). For microbiome data, we used the closed-reference BIOM table rarefied to 10,000 sequences/sample. For diversity changes between timepoints, we aggregated Shannon diversity values across groups of individuals (all, females, males) and calculated mean values and standard errors. All successfully processed samples (detected features in LC-MS or successful sequencing with 10,000 or more sequences/sample) were considered.

Beauty products and chemical standards

Samples (10 mg) from personal care products used during T0 and T7–T9 MSV000081580 (Additional file  2 : Table S1) and common beauty products used during T4–T6 MSV000081581 (Additional file  3 : Table S2) were extracted in 1 ml 50:50 ethanol/water. Sample extractions were subjected to the same UPLC-Q-TOF MS method used to analyze skin samples and described above in the section “ Metabolite extraction and UPLC-Q-TOF mass spectrometry analysis .” Authentic chemical standards MSV000081583 including 1-dehydroandrostenedion (5 μM), chenodeoxyglycocholic acid (5 μM), dehydroisoandrosterone sulfate (100 μM), glycocholic acid (5 μM), and taurocholic acid (5 μM) were analyzed using the same mass spectrometry workflow used to run skin and beauty product samples.

Monitoring beauty product ingredients in skin samples

In order to monitor beauty product ingredients used during T4–T6, we selected only molecular features present in each beauty product sample (antiperspirant, facial lotion, body moisturizer, soothing powder) and then filtered the aligned MZmine feature table (Additional file  5 : Table S4) for the specific feature in specific body part samples. After feature filtering, we selected all features that had a higher average intensity on beauty product phase (T4–T6) compared to non-beauty product phase (T1–T3). The selected features were annotated using GNPS dereplication output http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=69319caf219642a5a6748a3aba8914df , plotted using R package ggplot2 ( https://cran.r-project.org/web/packages/ggplot2/index.html ) and visually inspected for meaningful patterns.

Random forest analysis

Random forest analysis was performed in MetaboAnalyst 3.0 online platform http://www.metaboanalyst.ca/faces/home.xhtml . Using LC-MS1 features found in armpit samples collected on T3 and T6. Random forest parameters were set as follows: top 1000 most abundant features, number of predictors to try for each node 7, estimate of error rate (0.0%).

BugBase analysis

To determine the functional potential of microbial communities within our samples, we used BugBase [ 83 ]. Because we do not have direct access to all of the gene information due to the use of 16S rRNA marker gene sequencing, we can only rely on phylogenetic information inferred from OTUs. BugBase takes advantage of this information to predict microbial phenotypes by associating OTUs with gene content using PICRUSt [ 84 ]. Thus, using BugBase, we can predict such phenotypes as Gram staining, or oxidative stress tolerance at each timepoint or each phase. All statistical analyses in BugBase are performed using non-parametric differentiation tests (Mann–Whitney U ).

Taxonomic plots

Rarefied OTU counts were collapsed according to the OTU’s assigned family and genus name per sample, with a single exception for the class of chloroplasts. Relative abundances of each family-genus group are obtained by dividing by overall reads per sample, i.e., 10,000. Samples are grouped by volunteer, body site, and time/phase. Abundances are aggregated by taking the mean overall samples, and resulting abundances are again normalized to add up to 1. Low-abundant taxa are not listed in the legend and plotted in grayscale. Open-source code is available at https://github.com/sjanssen2/ggmap/blob/master/ggmap/snippets.py

Dissimilarity-based analysis

Pairwise dissimilarity matrices were generated for metabolomics and 16S metagenomics quantification tables, described above, using Bray–Curtis dissimilarity through QIIME 1.9.1 [ 71 ]. Those distance matrices were used to perform Procrustes analysis (QIIME 1.9.1), and Mantel test (scikit-bio version 0.5.1) to measure the correlation between the metabolome and microbiome over time. The metabolomics dissimilarities were used to perform the PERMANOVA test to assess the significance of body part grouping. The PCoA and Procrustes plots were visualized in EMPeror. The dissimilarity matrices were also used to perform distance tests, comparing the distances within and between individuals and distances from time 0 to times 1, 2, and 3 using Wilcoxon rank-sum tests (SciPy version 0.19.1) [ 19 ].

Statistical analysis for molecular and microbial data

Statistical analyses were performed in R and Python (R Core Team 2018). Monotonic relationships between two variables were tested using non-parametric Spearman correlation tests. The p values for correlation significance were subsequently corrected using Benjamini and Hochberg false discovery rate control method. The relationship between two groups was tested using non-parametric Wilcoxon rank-sum tests. The relationship between multiple groups was tested using non-parametric Kruskal–Wallis test. The significance level was set to 5%, unless otherwise mentioned, and all tests were performed as two-sided tests.

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Acknowledgements

We thank all volunteers who were recruited in this study for their participation and Carla Porto for discussions regarding beauty products selected in this study. We further acknowledge Bruker for the support of the shared instrumentation infrastructure that enabled this work.

This work was partially supported by US National Institutes of Health (NIH) Grant. P.C.D. acknowledges funding from the European Union’s Horizon 2020 Programme (Grant 634402). A.B was supported by the National Institute of Justice Award 2015-DN-BX-K047. C.C. was supported by a fellowship of the Belgian American Educational Foundation and the Research Foundation Flanders. L.Z., J.K, and K.Z. acknowledge funding from the US National Institutes of Health under Grant No. AR071731. TLK was supported by Vaadia-BARD Postdoctoral Fellowship Award No. FI-494-13.

Availability of data and materials

The mass spectrometry data have been deposited in the MassIVE database (MSV000081582, MSV000081580 and MSV000081581). Molecular network parameters for MS/MS data collected from all body parts of 11 individuals during T0-T9 MSV000081582 are accessible here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=284fc383e4c44c4db48912f01905f9c5 . Molecular network parameters for MS/MS data collected from armpits T0–T3 MSV000081582 and deodorant used by individual 1 and 3 MSV000081580 can be found here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=f5325c3b278a46b29e8860ec5791d5ad and here http://gnps.ucsd.edu/ProteoSAFe/status.jsp?task=aaa1af68099d4c1a87e9a09f398fe253 , respectively. OTU tables can be found in Qiita ( qiita.ucsd.edu ) as study ID 10370, and sequences can be found in EBI under accession number EBI: ERP104625.

Author information

Amina Bouslimani and Ricardo da Silva contributed equally to this work.

Authors and Affiliations

Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, San Diego, USA

Amina Bouslimani, Ricardo da Silva, Kathleen Dorrestein, Alexey V. Melnik, Tal Luzzatto-Knaan & Pieter C. Dorrestein

Department of Pediatrics, University of California, San Diego, La Jolla, CA, 92037, USA

Tomasz Kosciolek, Stefan Janssen, Chris Callewaert, Amnon Amir, Livia S. Zaramela, Ji-Nu Kim, Gregory Humphrey, Tara Schwartz, Karenina Sanders, Caitriona Brennan, Gail Ackermann, Daniel McDonald, Karsten Zengler, Rob Knight & Pieter C. Dorrestein

Department for Pediatric Oncology, Hematology and Clinical Immunology, University Children’s Hospital, Medical Faculty, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany

Stefan Janssen

Center for Microbial Ecology and Technology, Ghent University, 9000, Ghent, Belgium

Chris Callewaert

Center for Microbiome Innovation, University of California, San Diego, La Jolla, CA, 92307, USA

Karsten Zengler, Rob Knight & Pieter C. Dorrestein

Department of Bioengineering, University of California, San Diego, La Jolla, CA, 92093, USA

Karsten Zengler & Rob Knight

Department of Computer Science and Engineering, University of California, San Diego, La Jolla, CA, 92093, USA

Department of Pharmacology, University of California, San Diego, La Jolla, CA, 92037, USA

Pieter C. Dorrestein

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Contributions

AB and PCD contributed to the study and experimental design. AB, KD, and TLK contributed to the metabolite and microbial sample collection. AB contributed to the mass spectrometry data collection. AB, RS, and AVM contributed to the mass spectrometry data analysis. RS contributed to the metabolomics statistical analysis and microbial–molecular correlations. GH, TS, KS, and CB contributed to the 16S rRNA sequencing. AB and GA contributed to the metadata organization. TK, SJ, CC, AA, and DMD contributed to the microbial data analysis and statistics. LZ, JK, and KZ contributed to the additional data analysis. AB, PCD, and RK wrote the manuscript. All authors read and approved the final manuscript.

Corresponding authors

Correspondence to Rob Knight or Pieter C. Dorrestein .

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All participants signed a written informed consent in accordance with the sampling procedure approved by the UCSD Institutional Review Board (Approval Number 161730).

Competing interests

Dorrestein is on the advisory board for SIRENAS, a company that aims to find therapeutics from ocean environments. There is no overlap between this research and the company. The other authors declare that they have no competing interests.

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Additional files

Additional file 1:.

Figure S1. Beauty products ingredients persist on skin of participants. Figure S2. Beauty product application impacts the molecular and bacterial diversity on skin of 11 individuals while the chemical diversity from personal beauty products used by males and females on T0 is similar. Figure S3. Longitudinal impact of ceasing and resuming the use of beauty products on the molecular composition of the skin over time. Figure S4. Molecular networking to highlight MS/MS spectra found in each body part. Figure S5. Longitudinal abundance of bile acids and acylcarnitines in skin samples. Figure S6. Characterization of steroids in armpits samples. Figure S7. Characterization of bile acids in armpit samples. Figure S8. Characterization of Acylcarnitine family members in skin samples. Figure S9. Beauty products applied at one body part might affect other areas of the body, while specific products determine stability versus variability of microflora at each body site. Figure S10. Representation of Gram-positive bacteria over time and the molecular features from the shampoo detected on feet. Figure S11. Procrustes analysis to correlate the skin microbiome and metabolome over time. Figure S12. Correlation between specific molecules and bacteria that change over time in armpits of individual 11. Figure S13. Representation of the number of samples that were removed (gray) and those retained (blue) after rarefaction at 10,000 threshold. (DOCX 1140 kb)

Additional file 2:

Table S1. List of personal (T0 and T7–9) beauty products and their frequency of use. (XLSX 30 kb)

Additional file 3:

Table S2. List of ingredients of common beauty products used during T4–T6. (PDF 207 kb)

Additional file 4:

Table S3. Mzmine feature finding and crop filtering parameters. (XLSX 4 kb)

Additional file 5:

Table S4. Feature table for statistical analysis with blank filtering and total ion current normalization. (CSV 150242 kb)

Additional file 6:

Table S5. Feature table for individual feature abundance in armpits. (XLSX 379 kb)

Additional file 7:

Table S6. Feature table for Calour analysis. (CSV 91651 kb)

Additional file 8:

Table S7. Metadata for Calour analysis. (TXT 129 kb)

Additional file 9:

Table S8. feature table with Probabilistic quotient normalization for molecular–microbial analysis. (ZIP 29557 kb)

Additional file 10:

Table S9. OTU table rarefied to 10,000 sequences per sample. (BIOM 9493 kb)

Additional file 11:

Table S10. 16S rRNA sequencing read counts per sample. (TSV 2949 kb)

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Bouslimani, A., da Silva, R., Kosciolek, T. et al. The impact of skin care products on skin chemistry and microbiome dynamics. BMC Biol 17 , 47 (2019). https://doi.org/10.1186/s12915-019-0660-6

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An integrative approach to product development—A skin-care cream

Yuen s. cheng.

a Department of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong

Robert K.M. Ko

b Department of Biochemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong

Christianto Wibowo

c ClearWaterBay Technology, Inc., 4000 W. Valley Blvd., Suite 100, Pomona, CA 91789, United States

An integrative approach, involving marketing and management issues on the business side, and product design and prototyping on the technical side, is proposed for the development of chemical-based products. For the former, objective-time chart, RAT 2 IO modules and workflow diagrams are used for project management. For the latter, the integration of experiments, modeling and synthesis expedites product conceptualization and prototyping. Tasks for which chemical engineers are expected to play a key or a supporting role are discussed. An industrial application – the development of a skin-care cream is described alongside the procedure in order to illustrate the myriad issues in product development. In addition to the traditional engineering problems such as process and equipment design, product characterization, performance evaluation, and stability tests are also included as an integral part of this approach.

1. Introduction

Spurred by a changing global business environment, both industrial and academic leaders have been urging the chemical engineering community to expand our focus from commodity to high-value-added products and from process design to product development. These efforts have gradually taken roots. A large number of research papers ( Bagajewicz, 2007 ; Street, Woody, Ardila, & Bagajewicz, 2008 ; Wibowo & Ng, 2002 ; among others), review articles ( Gani, 2004a , Hill, 2004 , Wintermantel, 1999 ), textbooks ( Cussler & Moggridge, 2001 ; Seider, Seader, & Lewin, 2004 ) and monographs ( Bröckel, Meier, & Wagner, 2007 ; Ng, Gani, & Dam-Johansen, 2007 ) were devoted to the understanding of product development, and formulation of the relevant techniques.

The wide variety of activities in product development was summarized in a table by Ulrich and Eppinger (2004) , a modified version of which is presented in Fig. 1 . These activities span three phases in time – product conceptualization , detail design and prototyping , and product manufacturing and launch – and can be classified by job function in terms of management , sales and marketing , research and design , manufacturing , and finance and economics . The activities can also be grouped into various unit tasks , which may involve several job functions and last over more than one development phase. For example, economic analysis includes activities in both phase II and phase III, and involves manufacturing as well as finance and economics. Of particular interest are those activities, italicized in Fig. 1 , in product development that require the input of a chemical engineer. The execution of other activities within the same unit task may involve marketing and management. The key question is how to execute these unit tasks in a systematic manner to minimize the amount of time, effort and money for the development of chemical-based products. The rest of the issues in Fig. 1 such as product promotion and business management belong to other disciplines and will not be discussed in this article.

Classification of product development activities by phase and by task.

To formulate such a product development procedure, we will focus on a specific class of products—skin-care creams. Various issues related to product conceptualization of creams and pastes have been discussed by Wibowo and Ng (2001) . For example, the quality factors such as sensorial, rheological, mechanical, and physicochemical have been classified. These quality factors are related to the material properties such as viscosity, dielectric constant, and so on, as well as to how the constituents are assembled to form the microstructure of the product, as characterized by structural attributes such as particle or droplet size distribution, phase volume fraction, and particle shape. An understanding of the relationships between product performance, and material properties and structural attributes enables the designer to select the proper ingredients and design the manufacturing process to obtain a product with the desired performance. However, the proposed product development procedure has not been demonstrated by developing an actual product. In this study, we will expand this previous effort by collaborating with an industrial partner.

This article has two objectives. First, it attempts to put the various tasks for product development in proper perspective. The ways in which market demands are identified, product performance is evaluated and product reliability is tested have not received sufficient attention in the literature. Second, it illustrates the significance of integrating experiments, modeling, and synthesis for the development of a skin-care cream product. Despite the advances in engineering sciences, experimentation is crucial for the design of chemical products particularly those with an internal microstructure.

Although this integrative approach strives to offer a holistic view of product development, it is not necessary to cover all the relevant topics. Thus, we will focus on the italicized issues in red in Fig. 1 . The discussion will be organized as follows. We begin with a general discussion of the elements of the integrative approach. This will be followed by discussions on the relevant unit tasks: project management, market study, product design, feasibility study, and prototyping. The skin-care cream case study will be dispersed throughout the general discussion. The traditional chemical engineering issues in Fig. 1 such as scale-up studies and plant startup are not discussed. Also, some of the details related to the performance and stability of the specific skin-care cream under consideration are omitted as this commercial information is not central to the aim of this article.

2. An integrative approach

The starting point of a product development project is to formulate an Objective-Time Chart ( Fig. 2 ) ( Ng, 2004 ). This is part of the project management task in Phase I. It shows the objectives and subobjectives that have to be met in a given time horizon. For example, Objective D can be decomposed into subobjectives D1–D6. Subobjective D6 is further decomposed into D61–D65 and so on. This exercise is often used by a product/process development team to show all the team members the tasks that need to be performed and the time by which they should be completed. By offering a hierarchical view of the development project in its totality, every member knows what other members are doing to achieve the overall goal. Also, it highlights the tasks that can be carried out concurrently, thereby reducing the overall development time.

A generic objective-time chart.

Also shown in Fig. 2 is the RAT 2 IO Module that we specify for each objective or subobjective. The acronym stands for resources, activities, time, tools, input/output information, and objective. Thus, we identify in advance the resources (money and people) required to complete certain activities (experiments, modeling and synthesis) within a specified period of time using proper tools (experimental setup or software) to generate the necessary information and to meet the given objective .

The development of a consumer product such as a skin-care cream has been largely based on experience alone. While previous experience provides a good starting point, a substantial amount of experimental trial and error is often involved in the development of a new product. We submit that the product be synthesized by defining its constituents and microstructure, rather than simply screening different alternatives generated in a combinatorial manner. In doing so, understanding of the physical phenomena that control the product performance forms the basis for rationalizing the development process. Various models are utilized to describe the relationships among product performance, material properties, and product attributes, so as to establish a link between the targeted performance and the required technical specifications of the product. Experiments are used to support the modeling effort, as complete scientific elucidation of the underlying physical phenomena behind the technology of many chemical products is still a long way off ( Wintermantel, 1999 ). Thus, this integrative approach does not eliminate the need for previous experiences. Rather, it helps to organize them in a systematic way so that they can be better utilized in the development of a new product.

Fig. 3 shows a generic Workflow Diagram for product development which underscores the importance of iterations. It shows three iteration loops. The inner loop illustrates how the ingredients and processing conditions are modified to yield the desired product performance. This is achieved by using a combination of experiments, modeling and synthesis. The outer loop shows that the product quality factors are redefined after evaluation of a product prototype by a test panel. Sometimes, test marketing is carried out after small-scale manufacturing. The outermost loop (dotted line) represents the situation where market needs are re-examined after market testing.

A generic workflow diagram for product development.

3. Project management

The deceptively simple objective-time chart is what distinguishes an expert from a novice. An effective project manager with the right experience can draw up a realistic timeline, ensure the availability of the necessary manpower and financial resources, and follow through to facilitate the flow of input/output information from one subobjective to another. Thus, this manager should have a good appreciation of all the RAT 2 IO modules in a product development project although no one is expected to master all the details in every module.

3.1. Case study—skin-care cream

The target of this case study is a skin-care cream with new and improved functionalities. Based on the collective experience of all the team members, an objective-time chart ( Fig. 4 ) and the RAT 2 IO module for the overall product development project ( Table 1 ) were prepared.

Objective-time chart of the skin-care cream development project.

RAT 2 IO module for the overall product development project.

4. Market study

The decision for developing a product may be technology-push or demand-led. For the former, a product concept can be stimulated by the discovery of an ingredient which gives some new or improved function. As an example, hyaluronic acid is now a key ingredient in a number of products because of its moisturizing function. Examples for the latter include antiseptic hand cleansing gel and nano-silver mask that are now readily available after the outbreak of the SARS (Severe Acute Respiratory Syndrome) epidemic in 2003.

Irrespective of the driver for product development, as part of marketing, the engineers and scientists are often part of a team to form an image of the product and to define its functions to meet anticipated or existing market needs. This information can be collected from frontline salespersons, advertising agents and customers. Typical considerations include:

• • Is the product technology-push or demand-led?
• • Who are the target consumers for the conceived product?
• • Who are the competitors?
• • Does the demand for the product depend on season?
• • What is the market size of the candidate product?
• • What is the product image?
• • What packaging would be the most practical for the desired application?
• • Does the product fit in the company's product lines?
• • Can the company's technical strengths ensure product qualities?
• • Are the sales channels in place to effectively market the product?

Clearly, product conceptualization requires a combination of technical know-how and marketing experience. Often, it is easier for chemical engineers to pick up marketing knowledge on the job than for business personnel to acquire the technical skills.

4.1. Case study—skin-care cream

The antioxidant network of the skin is primarily localized in the epidermis and to a certain extent in the dermis. It is comprised of a variety of antioxidants, such as glutathione (GSH) and α-tocopherol (α-TOC), that protect skin against damaging effects from reactive oxygen species (ROS). It is now well established that solar UV radiation can stimulate ROS production in skin cells and skin tissue ( Hanson, Gratton, & Barden, 2006 ; Heck, Vetrano, Mariano, & Laskin, 2003 ), causing a dramatic decrease in such antioxidants due to the oxidative injury by these UV-induced free radicals. Also, ROS stimulate the synthesis of collagen-degrading enzymes known as matrix metalloproteinases. Loss of collagen, one of the primary structural components of dermis responsible for conferring strength and support to human skin, will lead to the appearance of wrinkles ( Craven et al., 1997 ). Given the causal role of ROS in skin aging and in the development of skin cancer ( Baumann, 2007 ), in addition to blocking the UV light, the supplementation of sunscreen with antioxidants represents a rational approach to ameliorating the solar UV-induced skin damage ( Farris, 2005 ; Thiele, Hsieh, & Ekanayake-Mudiyanselage, 2005 ; Weber et al., 1997 ).

This was achieved by developing a skin-care cream with two new ingredients, zinc oxide nanoparticles and an herbal extract. Zinc oxide is well accepted as a physical UV absorbent and has been widely used in sun-screening products. In this investigation, an antioxidant derived from Fructus Schisandrae (FS) was used due to its proven antioxidant function ( Ko & Mak, 2004 ). In addition, moisturizing function is also required.

4.1.1. Collecting customer needs

Some of the questions the business manager/engineer/formulator used to define the product are listed below:

• • Should the product be a facial or body product?
• • Should the product be a cream or lotion?
• • Should the product be adjusted depending on season?
• • Should the container be a tube, a glass jar or a bottle with a pump head?
• • Can other functions be included to make the product more attractive?

To shed light on the questions above, the following information/ideas/comments in the same order as the questions were collected from both frontline salespersons and engineers:

• • The quality requirements and, therefore, the formulas for these two products are actually different. The consumer usually demands a higher quality product for the face than for the body.
• • A lotion which spreads readily is more suitable for outdoors, a larger area such as the leg or body, whereas a cream is right for a smaller area such as the hand or face.
• • The majority of people accept the need to apply sun-screening products. However, sunscreen cream is perceived to be thick and greasy. They are used only in summer time during outdoor activities.
• • Since most consumers do not like a greasy feeling, a lotion or a light cream is preferred.
• • Since UVA (320–400 nm) can pass through glass ( Baumann, 2007 ), daily application of a sun-screening product with a moderate sun protection factor (SPF) value can be recommended for use indoors.
• • There is a higher demand for sun-blocking and whitening products in summer time. Products resisting dryness are usually in higher demand in winter and dry weather.
• • In the market, it is not difficult to find a day cream containing a moderate SPF value of 8–15 which can be used daily for all seasons.
• • It is rather difficult to retrieve the lotion at the bottom of a bottle with a pump head.
• • As recommended by an advertising agency, a bottle size of 50–100 mL is appropriate for a day cream.
• • Selling through chain retail stores can be arranged.
• • A retail price in the range of HK$150–350 per bottle should be considered.
• • Unlike other products, our product with an herbal antioxidant offers a unique selling point.
• • Strong scientific evidence that the herbal extract neutralizes UV-induced free radicals is needed.
• • Hyaluronic acid can be considered as a moisturizing agent. However, enhancers might be needed to promote its penetration into the skin ( Rieger, 1998 ).
• • Natural products are preferred to artificial ingredients. Mosquito repellent can be added to the sunscreen to form a multifunctional product.
• • After launching the first product, a series of related products derived from the first product can follow.

4.1.2. Identifying product quality factors

After a number of brainstorming sessions, it was decided that the product should be a light facial day cream with sun-screening, antioxidant and moisturizing functions. It would be an all-season product. The sun-screening ingredient should provide a natural look. This ruled out the use of microsized ZnO particles which reflect visible light and lead to whitening. From a sensorial point of view, improved spreadability and a less greasy feel was targeted.

4.1.3. Studying competing products

Intellectual property (IP) position is an important consideration for a company to commit considerable resources to launch a new product in the market. Skin care is a vast market with hundreds of different products. Table 2 shows the results of a patent search of six worldwide cosmetic companies on skin care applications, particularly those related to nanotechnology. Obviously, L’Oreal is the largest patent holder. Its “De-crease series” involves collagen biospheres that can penetrate into the skin and expand nine times of their volume when in contact with water in the skin to soften the expression lines ( L’Oréal, 2008 ). Shiseido developed the “O/W/O emulsification” technology in which superfine oil droplets are contained within water droplets in oil ( Yoshida et al., 1999 ). It allows two incompatible oils being used in the same formula. There are also products with vitamin E as an antioxidant on the market. However, it was decided that our day cream would be more suitable for our target customers.

Number of patents for six worldwide cosmetic companies in skin care and sun-screening and protection applications, without and with using nanotechnology.

5. Product design

Research and design tasks are performed in parallel with, rather than subsequent to, sales and marketing tasks. The objective is to translate the desirable quality factors identified by the marketing team into technical specifications, including the active and supporting ingredients to be included in the product as well as the structure of the product itself. A base-case recipe would be developed during this phase. During this process, the potential technical challenges and opportunities in making the product are identified; this information should be provided to the marketing team as product conceptualization is often a compromise between desirability and practicality.

Naturally, ingredients are selected based on their capability for performing a certain function. For products driven by the discovery of a functional ingredient, the active ingredient(s) are already fixed and the focus is on specifying the appropriate supporting ingredients such that the product possesses additional quality factors as desired by potential consumers. For demand-led products, the R&D activities begin with finding the suitable active ingredient(s). The chemistry knowledge provides a good starting point to identify potential candidates. In some cases, new molecules can be identified as the most feasible candidates based on chemistry insights. The candidates are then screened to identify a handful of lead compounds to be further investigated to verify their capability and to come up with the best choice. High-throughput screening techniques, which are capable of quickly testing a large number of samples for a particular response, are valuable tools to expedite such a search.

As an alternative to the experiment-based trial and error approach, model-based search techniques such as computer-aided molecular design and computer-aided molecular/blend design have been developed ( Achenie, Gani, & Venkatasubramanian, 2003 ; Gani, 2004b ). Starting from the specifications of the desired product, molecular structures or mixtures that satisfy the target can be found with the help of mathematical models for estimating the desired properties. In reality, the majority of chemical-based consumer product design problems are solved using a combination of experiment-based and model-based techniques, because validated mathematical models are not available for all desired properties and/or product performance evaluations. Model-based search techniques serve as valuable tools for identifying a small number of compound structures which possess the desirable properties, thereby greatly reducing the search space that has to be investigated experimentally using a trial and error approach.

The development of multifunctional products poses additional challenges such as the need to combine incompatible ingredients in a single delivery system. Supporting ingredients are normally chosen among commonly used materials, which for personal care products may have to be approved by the regulatory authorities. These supporting ingredients are often chosen based on previous experience with similar products, although such a choice can eventually be justified on scientific grounds.

In Phase I, the marketing plan and the product attributes may constantly change. As a consequence, the R&D plan has to be revised accordingly. For example, an extra active ingredient may need to be incorporated to achieve an additional quality factor because of a newly identified market demand. The engineer/chemist may have to look for a new ingredient and consider its compatibility with the existing ingredients.

5.1. Case study—skin-care cream

5.1.1. relating quality factors to technical specifications.

The target product was a day cream with sun-blocking, antioxidant and moisturizing functions. Two active ingredients, namely Fructus Schisandrae extract and zinc oxide nanoparticles, distinguish the product from its competition. In addition, the product has to possess additional rheological, sensorial and physical quality factors that are typical to a facial cream, which can be related to the ingredients, certain product attributes or technical specifications as indicated in Table 3 . These targets for the day cream were decided based on the collective experience of the development team. For the moisturizing function, a humectant or emollient can be added. Glycerol, propylene glycol and hyaluronic acid are commonly used for this purpose. For a product to spread readily, based on our own experience, a lotion or light cream with a viscosity between 6000 and 50,000 mPa s may give a more pleasant feel. The desired sensorial quality factors such as non-greasiness and softness are achievable by adjusting the emollient content, the ingredients and constituent droplet size. Furthermore, the use of appropriate emulsifiers with proper concentrations is critical to the stability of the product. The presence of zinc oxide particles in the formula can lead to whitening effect on the skin due to the reflection of visible light. This problem can be avoided by using zinc oxide nanoparticles.

Quality factors, the corresponding ingredients, product attributes and technical specifications, and performance tests.

5.1.2. Identifying the product microstructure

The day cream can be selected to be an oil-in-water (O/W), water-in-oil (W/O), or double (W/O/W or O/W/O) emulsion. Such a selection of product delivery vehicle should be driven by both practical considerations and consumer perception. A W/O emulsion is preferable from the dermatological point of view, since the lipid film on the skin favors oil-soluble active ingredients. An O/W emulsion is more appreciated by the consumer due to its less greasy feeling ( Spiess, 1996 ). In the end, the customers’ perception was deemed to be more important, and an O/W emulsion was chosen.

5.1.3. Choosing ingredients and base case formula

To come up with a base case formula, we have to decide on the key ingredients and their concentrations. In addition, supporting ingredients such as emollients, humectants, thickeners, stabilizers, emulsifiers, preservatives, and fragrances are also selected to meet the technical specifications. Table 4 lists some examples of commonly used supporting ingredients, along with their recommended concentrations and selection criteria. However, choosing among 15,000 commercially available materials is a daunting task ( Ash & Ash, 1994 ; Flick, 1991 ). Therefore, it is a common practice for experienced formulators or chemists to compile their own short list. The choice is also affected by other factors such as the availability in the market, regulatory control, and the cost of the materials.

Examples of excipients and the corresponding selection criteria.

Table 5 shows the base case formula (prototype 1) as well as prototypes 2 and 3 in subsequent iterations. Note that some of the chemicals go by their trade names. The zinc oxide nanoparticles obtained from Advanced Nanotechnology Ltd. (ZinClear-S_60CCT and ZinClear-S_60AB) were suspended in caprylic/capric triglyceride and alkylbenzoate, respectively. Both samples contain 60% of zinc oxide nanoparticles. The Fructus Schisandrae extract was produced in our own laboratory ( Luk et al., 2008a , Luk et al., 2008b ). These two key ingredients were mixed into the oil phase of the base case formula.

Formula of the skin-care cream with sun-screening, antioxidant and moisturizing functions.

Among the major concerns for selecting emollients are the product's greasiness, softness and stickiness upon application. Since market survey indicated that customers favor natural ingredients, sunflower oil (Sigma) and sweet almond oil (Sigma–Aldrich) were selected for this product. A silicon oil, dimethicone, was chosen due to its non-sticky, highly spreadable, and water repellent properties. Taking into account the oil contents in the zinc oxide suspension mixture, 1% sunflower oil, 1% almond oil and 2% silicon oil were used in the base case formula. The concentration of cetyl alcohol, a co-emulsifier, was kept at 1%. Note that a cream containing more than 2% cetyl alcohol might result in soaping effect. In addition, 0.2% of polyvinyl pyrrolidone (PVP)/dimethylaminoethylmethacrylate copolymer was used as a film former to promote the formation of a uniform sunscreen film on the skin upon applying the product in prototype 1. Carbomers (Carbopol ® 940, 941, Lubrizol) and xanthan gum (Sigma–Aldrich) were selected as thickeners, again on the basis of common usage. Glycerol (Sigma–Aldrich) and propylene glycol (Acros) were chosen as humectants. Ethylenediaminetetraacetic acid disodium salt dihydrate (Invitrogen) and a mixture of diazolidinyl urea and iodopropynyl butylcarbamate (Liquid Germall ® Plus) were used as the stabilizer and preservatives, respectively. Their compositions were selected based on the suggested concentrations in Table 4 . Fragrance was not considered in this formula.

The next step was to determine the usage of emulsifiers. In theory, emulsifiers should be selected based on the required hydrophilic–lipophilic balance (HLB) value, which can be calculated based on the overall HLB value of the oil mixture,

where HLB i and x i refer to the HLB value and the weight fraction of the oil component i . The HLB values of some common emollients and emulsifiers can be found from the catalogs provided by the suppliers and from literature. Some of these values are listed in Table 4 , Table 5 . Alternatively, the HLB values of different emulsifiers could be calculated based on their particular functional groups ( Vaughan & Rice, 1990 ). However, the HLB system does not provide a definite answer to the selection problem, as other properties such as the compatibility of ingredients, the viscosity of the continuous phase and size of the emulsion droplets could affect the rate of creaming or phase splitting ( Lissant, 1974 ), which dictates the stability of the emulsion system. Therefore, experienced formulators normally select an appropriate mixture of emulsifiers according to the types of emollients used. Experimentally, the required HLB value can be determined by mixing a pair of emulsifiers with high and low HLB values with the desired sample and see which HLB value yields a stable emulsion ( Courtney, 1997 , Uniqema Ltd., 2005 ).

The HLB values of Fructus Schisandrae extract and PVP/dimethylaminoethylmethacrylate copolymer were not known. It was decided that they could be ignored at this stage assuming that their contribution to the overall required HLB was not dominant. For this formula, the overall required HLB was calculated to be 9.9 using Eq. (1) . In general, a mixture of two emulsifiers with high and low HLB values would give better stability than a single emulsifier having the same HLB value. For example, stearth-2 and oleth-20, with HLB values of 4.9 and 15, respectively, can be mixed to match the required HLB value of 9.9 for the oil mixture. For prototype 1, a total of 5 wt% emulsifiers, 2.5% stearth-2 and 2.5% of oleth-20, was used.

6. Feasibility study

The objective here is to obtain a preliminary assessment of the manufacturing issues related to the perceived product, in order to judge the economic and operational feasibility of the manufacturing process. A procedure and heuristics for generating the process alternatives for making creams and pastes were discussed by Wibowo and Ng (2001) . Process alternatives for generating the desired microstructure should be identified. This will help provide an estimate of the product cost, and thus the selling price. Often, this is decided by a balance between an acceptable return on investment and the selling price of the products on the market. For a given production rate, material and energy balance analyses are performed to determine raw material consumption, waste generation, utility consumption, and the required processing time. The cost of raw materials, especially the active ingredients, often represents a major portion of the product cost. In addition to transportation costs, import and export taxes and advertizing costs must be considered as they often substantially affect the overall economics. Often, a trade-off exists between raw material cost and production cost, as lower purity raw materials may require expensive pre-treatment before it can be incorporated into the product. Some impurities are totally unacceptable. For example, the presence of heavy metals in a skin-care product, even at a very minute concentration, can lead to a disastrous product recall. Therefore, it is crucial to identify the raw material source. Availability and consistency of the supply of the raw materials, especially the natural herbs, should also be considered at this stage.

There is no alternative to environmental compliance. Although the base case recipe and the process plant are not very exact at this point, local environmental regulations should be consulted to check if there is any limit on the disposal of certain waste materials and whether such limits may lead to the need for expensive waste treatment facilities.

This is also the right time to consider whether to file a patent to secure an IP position for the product. For example, a patent can be filed for the skin-care cream formula. Since the composition has not been fixed, a wider range of compositions should be claimed to provide adequate protection. Because the manufacturing process tends to be generic for a particular type of products say creams and pastes, a process patent may not be of a high value unless the process involves a novel technology for making the product under consideration. In particular, technology for producing a key ingredient in the product may provide the company with a competitive advantage.

6.1. Case study—skin-care cream

6.1.1. identifying sources of raw materials.

Except for Fructus Schisandrae extract and possibly ZnO nanoparticles, all raw materials will be sourced around the world based on availability, quality and price. The main active ingredient, Fructus Schisandrae extract, is not available in the open market. For this reason, it will be manufactured on our own. Instead of starting with the fruits, an extract prepared by supercritical CO 2 extraction can be purchased in Mainland China. This will be further processed to obtain the desirable fraction. A new process has been developed for manufacturing nano ZnO via a one-step mechanochemical method by milling zinc sulfate heptahydrate and potassium hydroxide, with potassium chloride serving as the matrix salt ( Lu, Ng, & Yang, 2008 ). This reaction has economic potential for manufacturing high-quality ZnO nanoparticles.

6.1.2. Considering patent issues

Filing a patent for the optimized cream formula containing the ingredients is planned. Non-provisional patents have been filed for a process to obtain highly pure Schisandrin B and (−)Schisandrin B, a diastereoisomer, from Fructus Schisandrae using a series of extraction, chromatography, and crystallization steps. Thus, our product will be protected to some degree.

7. Prototyping

The prototyping activities focus on bench-scale experiments to make a prototype of the conceived product in order to test the product performance. The base case recipe identified in product design (Phase I) is used as a starting point for the first prototype, which is then subjected to a series of performance tests and iterations to come up with a product with the desired performance. All required tests and the amount of sample needed for each test should be identified, so that a sufficient amount of each prototype material can be prepared in advance.

Mixing sequence and technique in making a skin-care cream can have a significant impact on emulsion properties such as droplet size distribution, which affects the sensorial quality factors and stability of the product. Table 6 summarizes the general heuristics for mixing sequence and technique. While most of the heuristics are based on common practices, they can be derived from the basic knowledge of the underlying phenomena of emulsion formation.

Heuristics for mixing sequence and mixing techniques.

Detail design and prototyping is inevitably an iterative process. Depending on the product characterization and performance test results, the product formula has to be revised. Physicochemical insights and previous experience are used to guide the iteration process. Table 7 offers some guidelines for adjusting the recipe based on the test results. In making creams, it is important to understand how various ingredients, their composition, and the product microstructure affect the performance of the product. For example, product viscosity can be increased by using a higher concentration of thickener, while a smoother feel on the skin may be achieved by adjusting the oil to water phase ratio, using a different emollient, and so on. The modified recipe is then used for making the next prototype.

General considerations on improving cream formulation based on test results.

Typically, a number of standard performance tests are available for a specific class of products. For example, tests for hair conditioners include assessing the condition of real human hair after applying the conditioner. For a sunscreen cream, the skin protection factor is considered in a standard test. One should be aware of opposition from some quarters against using animals for product testing.

7.1. Case study—skin-care cream

7.1.1. fabricating prototype.

Each version of the prototype was inspected for its feel on applications, and stability. If the prototype failed the stability test, an improved version would be prepared based on heuristics and experience. A prototype that passed the preliminary inspections would undergo performance and stability tests. Further adjustments of the formula or fabrication procedure were made if the performance was not satisfactory. This iterative process continued until a satisfactory prototype was produced. For conciseness, the description below covers only three iterations although many more were actually made.

7.1.1.1. Prototype 1

The composition of prototype 1 is listed in Table 5 . A 200-g cream sample was prepared in order to obtain a sufficient quantity for performing the various tests. The ingredients were separated into three groups and mixed separately. The oil phase contained all the oil-soluble ingredients, the aqueous phase consisted of the water-soluble ingredients and the third group was the preservatives. The mixing procedure was developed based on the heuristics in Table 6 . The aqueous phase was prepared first by dispersing the thickener, Carbopol ® 940, in 80 g of water under mild heating and a stirring speed of 800 rpm using a magnetic stir plate. Most of the remaining components in the aqueous phase were mixed in a separate beaker and heated to 70 °C. These two solutions were combined at 70 °C after the thickener was completely dissolved. Triethanolamine, the pH modifier, was added last; the solution was thickened and the pH value reached 5–6. The oil phase was prepared by mixing cetyl alcohol, dimethicone, sunflower seed oil, and sweet almond oil under gentle heating. Zinc oxide suspension, Fructus Schisandrae extract, stearth-2 and oleth-20 were then added to the mixture sequentially. After raising the temperature of the oil phase to 70 °C, the oil phase was added to the aqueous phase slowly at a stirring speed of 1000 rpm. The mixture emulsified immediately and was left for natural cooling. The droplet size of the mixture was further reduced with the use of a hand-held mixer (Kenwood) for 3–5 min and then returned to moderate mixing, as excessive mixing might induce bubbles or weaken the thickeners. When the temperature of the emulsion reached 45 °C, the preservative phase was added with general mixing. The cream was then immersed in a sonication bath for 5 min to remove any trapped bubbles and was then allowed to cool to room temperature. According to the vendor of zinc oxide, the pH should not be kept below 7.5. Since the pH value for cosmetic products is usually limited to 5.5–8.0, we decided to maintain the pH value of this skin-care product close to 7.5 with the pH modifier.

7.1.2. Characterization of prototype

Prototype 1 was examined visually on whether an emulsion was formed and its stability against phase split. It was also characterized in terms of viscosity, pH as well as the feel on applications ( Table 8 ). The viscosity was measured by a viscometer (Brookfield DVII+ Pro) and the viscosity was found to be lower than the specification. The pH value was determined by a pH meter (Hanna Instruments, HI 9025). The average droplet size could be determined by viewing the emulsion droplets under a microscope and the particle size distribution by a PSD analyzer (Coulter, LS 230). An average droplet size of 1.4 μm was determined. The emulsion gave acceptable softness and a non-greasy feel. However, it left a sticky feel after applying on the skin.

Characterization and stability tests for prototypes 1–3.

Note . * : Tolerance of stability after one freeze/thaw cycle. Stable: change in viscosity < 10%, Acceptable: 10% < change in viscosity < 20%, Unstable: 20% < change of viscosity < 40%, Unacceptable: change of viscosity > 40%.

7.1.3. Stability tests

Simple emulsion is thermodynamically unstable and is expected to eventually separate into oil and aqueous phases. For a day cream, a minimum lifetime of 3 years without phase split or significant changes in color and odor is required. Instead of waiting for 3 years before product launch, an in-house stability test procedure was followed. The prototype was subjected to low temperatures (−15 and 5 °C), elevated temperature (48 °C) for 3 months, freeze/thaw cycle, high humidity, and so on. Only the freeze/thaw cycle test is reported here. The sample had to pass through two to three freeze/thaw cycles, each with temperature swinging from 48 °C, to room temperature, to −15 °C and then back to room temperature, with a duration of 24 h at each temperature. The appearance, pH and viscosity were tested after each cycle. The results of these tests are summarized in Table 8 . Phase separation occurred after the first freeze/thaw stability cycle for prototype 1.

7.1.3.1. Prototype 2

As shown in Table 5 , the amount of film former was reduced to zero to avoid the sticky feel. The amount of Carbomer was increased to 0.35 wt% to improve the cream viscosity. To improve stability, the emulsifiers were replaced by Polysorbate 20 and GMS 165 (a mixture of glycerol stearate and PEG-100 stearate, emulsifiers with high and moderate HLB values, respectively). A solid emollient, cocoa butter, was added to obtain a final HLB value of 11.7.

Prototype 2 was produced using the same procedure described above and the results for characterization and stability tests are listed in Table 8 . As for prototype 1, the emulsion formed immediately when the two phases were mixed. The cream softness and greasiness was acceptable. However, the viscosity was still far below the specification. The formula was still not very stable and a small amount of oil appeared after the first freeze/thaw cycle.

7.1.3.2. Prototype 3

To further increase the viscosity, xantham gum was used along with Carbopol ® 940 for a total thickener concentration of 0.55 wt% ( Table 5 ). This resulted in a viscosity within the acceptable range albeit on the low side. The stability was also improved by adding in one more emulsifier, steareth-2, with a low HLB value as suggested in Table 7 . The cream texture was acceptable and it successfully passed through two freeze–thaw cycles. The prototype was further optimized but the details are omitted here. In parallel, prototype 3 was used in performance tests.

7.1.4. Performance tests

The objective of performance tests is to verify, quantitatively if possible, the sun-screening, antioxidant and moisturizing functions of the product. These tests can be performed in-house but often they are eventually carried out by external testing laboratories that can certify the results. The degree of sun protection is quantified in terms of the SPF value. Some commercial skin analyzers are available to carry out various tests, such as skin surface hydration, serum content, pH, melanin erythema, transepidermal water loss, skin temperature, etc. ( Leyden & Rawlings, 2002 ). Relative modifications should be designed if the performance of the prototype does not meet the target values. Only the antioxidant function and SPF value for the selected prototype are reported here.

7.1.4.1. Animal test

A bioassay using rats was established for assessing the biological activity of the antioxidant-supplemented sunscreen. In this proof-of-principle study, two formulations of sunscreen, without or with supplementation with antioxidants derived from Fructus Schisandrae, were examined for their effects on the antioxidant status of rat skin tissue, without or with solar UV-irradiation. The enzymes that regenerate GSH from its oxidized form and decompose peroxides are glutathione reductase (GR) and glutathione peroxidase (GPX), respectively. These two enzymes are active and inducible upon oxidative stress. Topical application of antioxidant containing cream can diminish such oxidizing damage arising from UV-irradiation. This animal test aimed to investigate the antioxidant ability of Fructus Schisandrae-containing cream product by measuring the levels of GSH and α-TOC and the activities of GR and GPX after UV-irradiation. The results were compared with that of a control cream which was made based on the same procedure and formulation but without Fructus Schisandrae extract.

Adult female Sprague–Dawley rats were used in the experiment. Following an intraperitoneal injection of chloral hydrate at 350 mg/kg for short-term anesthesia, the animals were shaved on their back with an electric shaver followed by the application of hair removal cream. Two circular areas (37 mm in diameter) were marked on the shaved area. Each circle was divided into two semicircles as shown in Fig. 5 . An amount of 200 mg of FS cream was applied to each of the two left semicircles, and the same amount of control cream was applied on the two right semicircles. The creams were applied once daily on the corresponding areas for 6 days. On the 7th day, the creams were applied 1 h before UV-irradiation, and the rat was anesthetized by an intraperitoneal injection of phenobarbital (120 mg/kg). A solar simulator (Oriel #96000, 150-W) with an output of 10.88 mW/m 2 of UVA light (320–400 nm) and UVB light (290–320 nm) was used. The rat was placed 5 cm underneath the light source for 30 min so that the UV light could fall on the lower circular area on the back as shown in Fig. 5 , while the upper part was shielded by black paper and aluminum foil. After the UV exposure, the rat was killed by cervical dislocation, and skin tissues (epidermis and dermis) of the four areas were isolated from the rat. Skin tissue samples were homogenized followed by centrifugation. The supernatants were subjected to biochemical analyses on the level of non-enzymatic and enzymatic antioxidants. The details of sample preparation procedure of such biochemical analyses have been described elsewhere ( Chiu, Mak, Poon, & Ko, 2002 ).

Schematic diagram of animal model for testing the antioxidant effect of topically applied cream on skin without or with UV-irradiation.

Topical treatment with FS cream caused an improvement in antioxidant status of skin tissue, as evidenced by significant increases (18–25%) in tissue GSH and α-TOC levels, as well as increases in GR and GPX activities, when compared with those treated with control cream containing no FS ( Fig. 6 a–d). UV-irradiation depleted antioxidants in skin tissue to varying extents (16–23%), except for GPX which showed a significant increase in enzyme activity (16%), an indication of increased oxidative stress. The beneficial effect of FS cream on skin tissue became more apparent after UV-irradiation. The UV-induced depletions of skin antioxidants were significantly ameliorated by FS cream pretreatment. The enhancement of antioxidant status of skin tissue by FS cream was further evidenced by the measurement of tissue malondialdehyde (MDA) production, an indirect index of free radical-induced oxidation of lipids. While FS cream treatment decreased the extent of MDA production (by 15%) in skin tissue without exposing to UV, it also suppressed the UV-induced increase in MDA production (by 10%) ( Fig. 7 ).

Effect of topical FS cream pretreatment on the antioxidant status of rat skin tissue, without or with UV-irradiation. The antioxidant status of skin tissue after the UV-irradiation, was assessed by measuring (a) reduced glutathione (GSH), (b) α-tocopherol (α-TOC) levels, (c) glutathione reductase (GR) and (d) glutathione peroxidase (GPX) activities. Values given are mean ± S.E.M., with n  = 4. a Significantly different from the control cream without UV-irradiation; b significantly different from the control cream with UV-irradiation.

Effect of topical FS cream pretreatment on of rat skin tissue, without or with UV-irradiation, as measured by malondialdehyde production. Values given are mean ± S.E.M., with n  = 4. a Significantly different from the control cream without UV-irradiation; b significantly different from the control cream with UV-irradiation.

7.1.4.2. SPF test

The SPF test procedure was simplified from the method suggested by FDA ( Food & Drug Administration, 1978 ). For a light source with a fixed energy output, the SPF value is the ratio of the time to produce the minimal erythema dose (MED) on protected skin and that on unprotected skin:

The artificial light source was the same solar simulator used in animal test. The power of UVA and UVB at the exit port was measured as 3.891 × 10 −3  W m −2 and 3.518 × 10 −3  W m −2 , respectively.

Test sites on the arm of a volunteer were used for reason of convenience. Four sites, 2.5 cm in diameter each, were marked with ink. They were exposed to the exit port of the instrument for 60 s, 75 s, 94 s, and 117 s, respectively. Other areas were covered by black cardboard. The sites were inspected 24 h later for the intensity of erythema. For this volunteer, minimal erythema was observed on the test site which had been exposed for 94 s and this was recorded as the MED for unprotected skin.

Test sites on the other arm of the same volunteer were used for determining MED for protected skin. According to the zinc oxide supplier, a day cream containing 9.6% ZnO would result in an SPF of around 8. Thus, the time for the MED of protected skin was expected to be around 752 s (i.e., 8 × 94 s). 2 mg/cm 2 of the prototype cream was applied on three test sites at least 15 min before UV exposure. Then the protected sites were exposed to same UV intensity for 420 s, 600 s and 752 s, respectively. Again, the rest of the arm was covered with black cardboard. Erythema was observed on the site with 600 s exposure, resulting in an SPF value of 6.4 which does not meet our target value of 8–15 ( Table 3 ). Clearly, more subjects should be used to increase the accuracy and an increase in the concentration of zinc oxide should be considered. These detailed will not be further discussed here.

8. Conclusions

Product development is a hierarchical, multiscale, multidisciplinary and iterative activity. It is hierarchical in the sense that decision-making progresses from objective to subobjective with increasing levels of details, while keeping in mind the overall product development project. The objective-time chart ( Fig. 2 ) reflects this hierarchical thinking, which is in a way a simple extension of the hierarchical process design method proposed by Douglas (1988) . Also well-recognized is the multiscale nature of product development in that the time and length scales of the relevant physicochemical phenomena, production activities, and logistics and transportation beyond the manufacturing plant differ by orders of magnitude ( Charpentier, 2007 ; Grossmann & Westerberg, 2000 ; Lerou & Ng, 1996 ). Product development inevitably involves professionals in sales and marketing, law, project management, advertising, and financial analysis. This multidisciplinary nature is captured in Fig. 1 where the activities in product development are classified by phase and by job function, and several unit tasks are identified. In fact, on the technical side, there are also chemical-based products in science and engineering areas such as medicine, healthcare, foods, electronics and information technology that are not the primary domain of a typical chemical engineer. The need for iterations in product development is represented by the workflow diagram ( Fig. 3 ). A product that warrants the significant investment associated with product launch demands detailed consideration from all angles.

To achieve product development with the least amount of time, effort and money, we believe systematic product development procedures and methods are essential. This skin-care cream case study provides a concrete example to illustrate the multitude of issues. On product conceptualization, chemical engineers have to actively collaborate with other professionals on business decision-making. While science and engineering can address how-to-make by selecting suitable materials and processing techniques, what-to-make inevitably involves marketing, IP position, and a host of environmental and safety issues. On research and development, the use of experiments, modeling and synthesis in an iterative manner is the key for prototyping.

The generic issues and approach for each unit task discussed in this paper are applicable for developing any given class of products. However, the heuristics, experiments and models are expected to be product class-specific. It is unlikely that the development team can come up with the best execution plan for a new product if the team does not have previous experience in working with the relevant line of products. In fact, the final objective-time chart ( Fig. 4 ) and the RAT 2 IO module for the overall skin-care cream development project ( Table 1 ), and the workflow diagram for iterations in prototype fabrication ( Fig. 8 ) and the corresponding RAT 2 IO module ( Table 9 ) actually took shape towards the end of this study. Nonetheless, these can certainly be used to expedite the development of similar products in the future. The importance of performance tests in product development was demonstrated. A bioassay, which involved live skin preparation, was essential for assessing the antioxidant activity of the cream formulation. Along with measurements for the sun-screening and moisturizing functions, they serve as measures for optimizing the formulation of sunscreen cream.

Workflow diagram for iterations between choosing formulation ingredients and performance testing.

A RAT 2 IO module for prototype fabrication.

As the scope of the chemical industry expands from commodity chemical business to include the manufacture and sale of higher value-added products, many new opportunities emerge for chemical engineers to contribute in product development. An obvious question would be, what are the market segments that chemical engineering as a profession would like to engage in? A similar question was posed by the processing community in China ( Ng, Li, & Kwauk, 2005 ). In addition, in each market segment, what are the tasks that a chemical engineer would like to and can perform? These questions have ramifications in what we consider to be a typical chemical engineering curriculum. The possible inclusion of business subjects in a chemical engineering education has been discussed by Landau (1997) , Ng (2002) , Ng and Wibowo (2003) and Wei (2008) . The concept of unit operations has served process design well by providing the building blocks for process flowsheeting. Now, can the concept of unit tasks with their associated RAT 2 IO modules, properly defined, categorized and enriched with the necessary technical as well as non-technical details, serve as the building blocks for product development? Efforts to address some of these issues are underway.

Acknowledgments

We thank our industrial partners at Karsten Enterprises Ltd. for providing the ingredients as well as advice on cream formulation and performance testing.

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The Year That Skin Care Became a Coping Mechanism

By Jia Tolentino

Over the summer, in one of many small, ridiculous attempts to affirm to myself that I will outlive the Trump Administration, I decided to incorporate both retinol and sunscreen into my daily skin-care routine. Both were recommended to me last year by a dermatologist. Retinol is an anti-aging ingredient, and I flinched, a little, fancying myself too young, at twenty-eight, for the Sisyphean hobby of trying to halt the effects of time on one’s body. But I went home and did some research, clicking around various beauty publications while checking the news on my Twitter feed, which every few seconds loaded a fresh batch of disorientation and dread. The Web sites told me that I should have started retinol earlier . I thought about the moment, a few weeks after the election, when I found my first gray hair, and how, soul-wise, several thousand years had passed since then. Skin seemed like a nice controllable project. As it turned out, it both was and was not.

In recent years, the concept of skin care—specifically, of skin care as a phenomenon that invites unlimited expenditures of money, strategy, and time—has exploded kaleidoscopically. The Korean beauty industry has popularized, globally, the idea of a nightly ten-step program. (For example: cleanse, double cleanse, exfoliate, tone, spray yourself with “essence,” use an “ampoule,” apply a sheet mask, add eye cream, moisturize, moisturize again.) The invention of selfie-friendly sheet masks —individually packaged pieces of fabric that are soaked in serum and look ridiculous when applied—has ushered in a per-use price point. (They run from a few bucks to an astonishing twenty dollars each.) Before my recent deep dive, I’d thought of myself as fluent in beauty products: I am vain and from Texas, and also a former women’s-media editor. But the ingredients I knew about—vitamins, antioxidants, acids—now inhabit a climate of techno-surrealism: there are products with donkey milk, snail slime, placenta cream, pig collagen; there are face helmets that blast you with infrared light. I started lightly spiralling. I followed one tweet to a Sunday Riley lactic-acid serum that cost a hundred and sixty dollars, another to a Shiseido essence (a sort of very special water) that cost one-eighty. The New York home page recommended a cleanser that made your dead skin cells come off like eraser scraps. I bought it, along with a bunch of other stuff, unsure if I was buying skin care or a psychological safety blanket, or how much of a difference between the two there really is.

When my skin feels good, I feel happy: my skin is a miraculous six-pound organ that keeps my blood and muscle from spilling all over the C train, and I’d like to treat it well. At the same time, it’s impossible to ignore that the animating idea of the beauty industry is that women should always be working to look better, and that means, in our culture, that we should always be working to look as young as possible—shielding ourselves from what Susan Sontag , in her essay “The Double Standard of Aging,” calls the “humiliating process of gradual sexual disqualification.” The beauty industry functions partly by solving a “crisis of the imagination,” as Sontag puts it—the ambient fear that you will be less beautiful in the future, and that some obscure but awful consequences might result. This fear is both artificially imposed and pragmatic: as long as women are broadly objectified, beauty will function as value, and its absence as lack.

As feminist discourse has gone mainstream, the beauty industry has tried to cover some of its tracks. At the Times Magazine, Amanda Hess recently wrote about how the term “anti-aging” is going out of fashion : instead of youthfulness, advertisers promise radiance. This is not a revision of beauty standards, Hess observed: it’s a rebranding, in which “young” is positioned as a synonym for “natural,” despite the fact that nothing is more natural than getting old. Something similar is going on today with a certain popular beauty look, which we might label “Instagram model.” The look evokes both nakedness and airbrushing and is made possible by technology. A lot of the work formerly performed by makeup has been redirected into products and procedures—eyelash extensions, micro-current facials, injections of all kinds—leading to, and prompted by, an aesthetic of militant naturalness surrounded by an unambiguous aura of money and work. It’s a regime posing as a regimen. “Rules of taste enforce structures of power,” Sontag wrote. The beauty industry runs on its ability to redefine “natural” at increasingly higher prices.

At the same time, the Internet’s destabilizing and democratizing tendencies have transformed the industry. I wrote to Alexis Swerdloff, the editor of New York’s The Strategist, which offers highly edited shopping guides; she pointed out that cheap, formerly hard-to-access Asian brands are now available online, and that women are increasingly looking to sources like Reddit for product recommendations, “which makes everything feel less force-fed to you by Big Beauty.” (A particularly popular post on The Strategist this year was written by Rio Viera-Newton, a nonprofessional enthusiast who detailed the Google doc she kept about her skin-care routine.) There’s also something perversely, unexpectedly hopeful about skin care in today’s political context. Traditionally, skin care represents an attempt to deny the inevitability of the future. For me, right now, it functions as part of a basic dream in which the future simply exists . I recently wrote about the embattled millennial generation , whose members overwhelmingly do not believe that we will receive the Social Security benefits that we are paying for, and for whom conversations about having children commonly invoke fears of climate destruction and violent nationalism and nuclear war. I wonder if women my age are less afraid of looking older than we are of the possibility that there will be no functional world to look old in. Sontag wrote, about anti-aging, “The collapse of the project is only a matter of time.” At the moment, that thought applies much more broadly.

The idea of beauty as a site of resistance rather than capitulation is often traced back to Audre Lorde, who, in 1988, wrote, “Caring for myself is not an act of self-indulgence, it is self-preservation, and that is an act of political warfare.” The context for these words is Lorde’s fight against liver cancer as well as the intersectional politics that she theorized as a black lesbian feminist. But her thought, in a much diluted iteration, has led to the popular idea of “ self-care ,” in which there is moral and political utility in relaxing with your sheet mask. And there can be—although it’s up to us to reframe beauty as the means to something, rather than, as the market would have it, an end in itself. “I think a lot about beauty as propaganda for a success story,” the writer Arabelle Sicardi wrote to me in an e-mail. “We want to be able to not have our suffering visible.” Beauty is a tool that tends to serve those in power, she wrote, and, at the same time, it fundamentally involves acts of witnessing the body, helping it to endure its conditions. This paradox becomes clearer to me each night, patting my face with serums while looking one-eyed at Twitter, using these apparatuses of self-loathing in an attempt to pronounce some form of love.

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SELF’s Comprehensive Skin-Care Routine Guide

By Sarah Jacoby and Mara Santilli

Reviewed by Michele S. Green, MD

All products are independently selected by our editors. If you buy something, we may earn an affiliate commission.

During these unpredictable pandemic times (after which the word “uncertainty” will be triggering for years) one thing has remained constant in many of our lives: a skin-care routine. Maybe yours is modeled after an influencer’s 11-step regimen, or you’re more of a wash, rinse, repeat person. Perhaps your skin-care routine has stayed exactly the same as pre-pandemic, or you’ve added additional steps, like a weekly mask or nightly serum for some extra self care. Or, it could be that you’re here to find out the best order of skin-care products once and for all (you’re in luck).

The truth is that each skin-care routine is necessarily as unique and individual as the person following it (or attempting to, anyway). But as skin care has become trendier on social media and thousands of new products have been released in recent years (containing seemingly every ingredient under the sun), it’s also gotten a little more intimidating and confusing for a beginner to get started—and for anyone to understand how to create an effective skin-care routine that works for them.

That’s where we come in. As you begin (or continue) your skin-care quest, we hope to answer as many of your questions as we can here in this skin-care 101 guide—with the help of research and experts rather than hype. Read on to find out everything you’ve ever wanted to know about all the potential skin-care routine steps and ingredients, including what you should keep in mind based on your skin type and any health conditions you may have.

Here’s how to use this guide: If you’re brand-new to the idea of a skin-care routine, it helps to start at the very beginning, where we answer your most basic questions about skin care—even the ones you may be too embarrassed to ask all your skin-care-savvy friends. If you’ve dabbled in skin care and just really want to know what ingredients might be right for you, we’ve got you too. Scroll down to learn more about the actual elements in a skin-care routine and get an overview of active ingredients that work best for certain skin conditions. We also have specific sections for skin of color, what to do if you’re pregnant, and what to keep in mind if you have a diagnosed condition that affects your skin. Plus we break down some often confusing aspects of the skin-care industry, such as whether or not the Food and Drug Administration (FDA) regulates skin-care ingredients and what exactly manufacturers mean when they call their products “natural” or “clean.”

In each section, you’ll find links to all our coverage on that topic, so make sure you click on anything that piques your interest if you want to learn even more.

And lastly, don’t forget to check out our glossary of popular skin-care terms , which can help clear up any lingering confusion you have, and these helpful tips on how to wash your face .

Let’s get started!

What do you mean when you say “skin care”? | Why should I care about skin care? | What do I need to know before I begin a skin-care routine? | What are the basic steps of a skin-care routine? | How do I address a specific skin issue? | How do I know which active ingredients are right for my skin? | What else should I know about skin-care ingredients? | Is there anything I need to know about caring for my skin of color? | What products are safe for pregnant people? | What if I have a medical condition that affects my skin? | What about “clean” beauty? | Which products do you like best?

What do you really mean when you say “ skin care ”?

We mean the basic care and keeping of your largest organ—your skin! It plays an important role in protecting you from outside pathogens and, you know, holds all your internal organs in place (phew). And in the same way that you regularly brush your teeth, your skin requires at least some attention to keep it functioning properly.

It also requires protection—especially from skin cancer . At SELF, when we talk about skin care we’re talking about science-backed ways to improve both the look and function of your skin to address and manage both cosmetic and medical concerns.

This guide is for anyone who is curious about what it means or what it takes to have an effective skin-care routine—from beginners who don’t know where to start all the way to seasoned skin-care enthusiasts. Consider it your ultimate skin-care manual.

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Why should I care about skin care?

Yes, caring about skin care might be quite trendy these days, especially with beauty influencers demoing everything from facial steaming to jade rolling on social media, but no matter what, giving your skin some love has both cosmetic and medical benefits. For instance, although you can’t slow down the passage of time, with a finely tuned skin-care regimen you can reduce the appearance of fine lines, wrinkles, dark spots, and sun damage. You can also quite effectively manage some more minor skin concerns, such as dryness or oiliness, with face care products.

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For those with specific skin conditions such as psoriasis , eczema , rosacea, and acne, skin care isn’t always optional and requires a bit more thought about ingredients that will be safe for your skin. For one, treating a specific skin condition often means you need to employ a particular skin-care regimen, and for another, your condition may make your skin more sensitive to ingredients and products in general. Finding a skin-care routine that works can offer a vital way for someone to manage and treat their condition.

There’s also the fact that many people find their skin-care routines offer some mental health benefits—having that routine may help you realize just how easy it can be to do nice things for your body and build healthy habits. “A consistent, healthy routine is important for establishing rhythm and order in our lives,” Corey L. Hartman, M.D. , founder of Skin Wellness Dermatology and assistant clinical professor of dermatology at the University of Alabama School of Medicine , tells SELF. “Whether the routine is skin care, exercise, meditation, or any other beneficial activity, the dedication to the method can bring grounding to our everyday lives, which can often feel chaotic and uncontrolled.”

Some people may also find that going through their routine or even applying the occasional mask relaxes them and helps them focus their attention on themselves, maybe for the only time in their day. Two great examples of this are “ Why I Embraced Skin Care After My Mother’s Death ” and “ How Skin Care Became a Crucial Part of My Sobriety Toolbox ,” personal essays we’ve published in recent years.

That said, some skin-care companies make a lot of big claims about what their products can do without necessarily having the evidence to back them up. At SELF, our aim is to help you make the most informed decision before buying or trying a product and to guide you toward the treatment options we know the most about.

I’m ready to start a skin-care routine. What do I need to know before I begin?

Before figuring out what to include in your skin-care routine, it’s important to know your skin type and if you have any major concerns you want to address. It’s also good to remember that everyone’s regimen is individual—what works for your friends, family, or randos online may not be best for you.

To figure out your skin type, think about how your skin acts without any makeup or products on it a few hours after taking a shower. If it gets a little greasy or shiny, you probably have oily skin. “If you tend to have eczema and your skin gets really dry in the cold winter months, then gravitating toward skin care for more sensitive, dry skin is best,” Sandy Skotnicki, M.D. , founder of Bay Dermatology Centre and assistant professor of dermatology the University of Toronto , tells SELF. “Most people have a combination, with oily areas around the nose and chin in a typical pattern,” she adds. It might also be possible that you don’t have any of these types, which means most skin-care products will be safe to use on your skin. Knowing your skin type will help steer you toward products that will manage dryness and oiliness while effectively taking care of any other skin concerns you have.

You don’t necessarily need to see a dermatologist before starting a skin-care routine. But if you have sensitive skin (or aren’t sure if your skin qualifies as sensitive), if you have a skin condition, or if you’re trying to address any major concerns (such as stubborn or severe acne or hyperpigmentation), it’s important to check in with a board-certified dermatologist who can guide you through the process.

Here are some great articles that can help you before you begin a skin-care routine:

• How to Know If You Should See an Esthetician or a Dermatologist
• How Bad Is It to Switch Up Your Skin-Care Products All the Time?
• How to Wash Your Face for Clearer, Healthier Skin
• Ask a Beauty Editor: Why Is My Skin Always Oily Halfway Through the Day No Matter What?

Okay, got it. So what are the basic steps of a skin-care routine?

Skin care doesn’t have to be complicated if you don’t want it to be, but in general there is an ideal skin-care routine order that helps ensure the products you use will be most effective. The three basic skin-care routine steps are cleansing, moisturizing, and applying sunscreen (look for at least SPF 30 and “broad spectrum” on the label). Your morning skin-care routine should include those basics: washing with a cleanser, slathering on a moisturizer, then putting on your sunscreen, says Dr. Skotnicki. Pro tip: You can use a moisturizer that has at least 30 SPF and broad-spectrum protection to combine those two steps.

When it comes to choosing a sunscreen you have options of physical sunscreens or chemical sunscreens. “Chemical sunscreens have ingredients like avobenzone that absorb the sun’s rays like a sponge, then release them in the form of heat,” Dr. Skotnicki explains. Physical sunscreens, or mineral sunscreens, have mineral ingredients, like zinc oxide or titanium oxide, and form a barrier that blocks the sun’s rays.

You can use either type of sunscreen as long as you’re consistent, Hysem Eldik, M.D. , a board-certified dermatologist at Marmur Medical in New York City, tells SELF. Some people might find that most mineral sunscreens don’t blend well with their skin tone and/or makeup, though, so it may take some trial and error to find the right one for you.

Your night skin-care routine, on the other hand, might include additional steps. If you wear heavy makeup or sunscreen during the day, you may find that your cleanser doesn’t get all your makeup off or still leaves you feeling kind of greasy. In that case, you might benefit from double cleansing, a process in which you wash first with an oil-based cleanser followed by a water-based cleanser or micellar water on a cotton pad to remove anything left behind. But double cleansing is not a requirement, don’t worry.

After cleansing, it’s time to apply any serums, toners, face exfoliators , or prescription treatments, depending on your skin concerns or goals. Then, you’ll want to seal these middle skin-care routine steps with a moisturizer. You can use a daytime moisturizer with SPF at night, too, although you may find that a thicker product is more moisturizing and better suited to nighttime use because you don’t need to worry about being able to put makeup over it—plus, you don’t need to be concerned about SPF while you’re sleeping.

If you’re feeling trendy , you might finish off your skin-care routine with a facial oil as your moisturizer (or on top of it). But just be careful with that, especially if your skin tends to be oily. “Although oils can provide superior hydration, they can come at the cost of clogging pores,” Dr. Eldik says. In that case, hydrating oil-free serums containing ingredients like hyaluronic acid and squalane might be a better formula for you. If you don’t have oily or acne-prone skin at all, however, a facial oil might work well for you and you may prefer that texture to a thicker cream or lotion moisturizer.

Read more about the basic steps of a skin-care routine:

• Your Skin-Care Routine Actually Only Needs These Three Things
• Here’s Exactly How and When to Use 5 Basic Skin-Care Staples
• Is Double Cleansing Truly Worth Your Precious Time?
• How to Find a Moisturizer That Won’t Leave Your Face a Greasy Mess
• How to Pick the Best Sunscreen for Your Lovely Face
• How Much Does the Order You Apply Your Skin-Care Products Actually Matter?

Sounds doable. But I also want to address a specific skin issue. How do I do that?

This is where products that contain specific active ingredients—known as just “actives” by skin-care enthusiasts—come in. Active ingredients are chemicals or compounds in face care products that are actually treating your skin for the concern the product is supposed to treat it for. For example, if you buy a product to help treat your acne, the active ingredient is the ingredient doing most of the work to clear up your acne.

Some actives may be broken out on a product label in a drug-facts box because they’re regulated more tightly by the (FDA). But in general, the FDA doesn’t test cosmetic skin-care products for safety or efficacy, so we don’t really know how well they work most of the time. That’s why there’s always some trial and error inherent in figuring out a skin-care routine for your specific skin.

The use of most actives is based on some research though, so we have at least a theory about what they can do and how well they do it.

Read more about active ingredients:

• What Exactly Are ‘Actives’ in Skin-Care Products?
• Here’s How to Build Your Tolerance to Irritating Skin-Care Products
• How to Care for Your Angry Skin After an Allergic Reaction on Your Face

Great. So how do I know which active ingredients are right for my skin?

Picking the right active ingredients depends on the specific skin concerns you’re hoping to address. Here are a few of the most common issues:

Some common signs of aging include photodamage dark spots, fine lines, wrinkles, and sagging skin.

Ingredients

Ceramides : Ceramides are intercellular lipids, meaning they fill in the spaces between your skin cells in the stratum corneum (the outer protective layer of skin). Your skin already makes ceramides on its own—without them, your skin won’t be able to effectively hold moisture in or keep irritants out. Topical ceramides may be present in both prescription treatments for eczema and over-the-counter products.

Niacinamide: This is a form of vitamin B3 (niacin) that can be applied to the skin. There is some research to suggest that it can be helpful for managing acne, rosacea, and signs of aging including hyperpigmentation, fine lines, and wrinkles. 1

Peptides : Peptides are known as the building blocks of proteins. They’re made up of short chains of amino acids. In the realm of skin care, we mostly talk about peptides as building up collagen, a protein your skin needs to keep its structure. Different types of peptides might do the job of bolstering your collagen in different ways, but the most common ones are signal peptides, which can both stimulate the skin’s collagen production, especially overnight, and slow down the natural breakdown of collagen.

Retinoids : These compounds—retinol, retinal (or retinaldehyde), retinoic acid, and synthetic retinoids like Adapalene and Tazerac—are one of only two proven ways to prevent the signs of aging. (The other is sunscreen!) Retinoids, which are forms of vitamin A, work by stimulating the skin-cell-shedding process from below, leading to smoother skin and a reduction in both signs of aging and acne.

These come in both prescription and over-the-counter products, typically with a concentration of 1%, so if you aren’t satisfied with the results of an over-the-counter option, check with a dermatologist about getting a prescription version. If you’re using it to address signs of aging like fine lines, Dr. Skotnicki recommends starting to use retinol products around age 30 to get ahead of the game. Retinoids are also notorious for causing irritation when you first start using them, so it’s crucial to apply them just a few days a week to start with and to apply a moisturizer right after using them.

Sunscreen : You’ve likely used a sunscreen before to prevent sunburns, which are one form of UV damage. But did you know that UV rays can also contribute to other kinds of damage? And that damage can cause dark spots, wrinkles, and other signs of aging? It’s true. Preventing that—and skin cancer, of course—is a major reason to use sunscreen every single day. Be sure to use a sunscreen that’s at least SPF 30 and provides broad-spectrum protection, meaning it protects against both UVA and UVB rays. Although the sunscreen in your makeup doesn’t count as your daily SPF, the sunscreen in your moisturizer can—as long as you use it on your ears and neck as well as your face.

Vitamin C : Yes, that vitamin C! This vitamin is essential for producing collagen and other important compounds in the body. And when it’s applied topically it can function as an antioxidant, thus preventing UV-related damage. It can also inhibit the production of melanin (pigment) in the skin, making it a good option for lightening dark spots due to photoaging or other kinds of damage. But beware that all forms of vitamin C are not created equal—some are more or less effective or stable than others. You should incorporate vitamin C at a concentration of about 10% in order for it to be effective at fighting sun damage, Dr. Skotnicki says. Also know that vitamin C often appears on the label as these derivatives: look for ingredients such as magnesium ascorbyl phosphate, ascorbyl 6-palmitate, ascorbic acid sulfate, or L-ascorbic acid (also referred to simply as ascorbic acid).

More on ingredients for aging:

• Can People With Sensitive Skin Be in the Retinoid Club Too?
• The Best Antioxidants for Skin, According to Dermatologists
• What Niacinamide Can—and Can’t—Do for Your Skin
• The 8 Best Retinol Creams, According to Dermatologists
• Why Just About Everyone Should Think About Using a Ceramide Cream
• Ask a Beauty Editor: What Do I Need to Look for in a Vitamin C Serum?

Although it’s very common, acne is a lot more complicated than most of us realize. For instance, there are different types of pimples (whiteheads, blackheads, et cetera), which may be inflamed (red, swollen, painful) or not. Acne can also be influenced by many factors in your life, such as your hormones. So if your acne is severe or if your over-the-counter treatment options aren’t helping, it’s important to see a dermatologist who may be able to prescribe you something more effective.

You may come across over-the-counter acne treatment products or other skin-care and cosmetic products that have “non-comedogenic” on the label. That’s because the technical term for a pore is a “comedone,” Dr. Eldik says, and acne is the result of a clogged pore. “Any product that irritates or clogs the pores can stimulate the cascade of acne,” he explains. So basically, the goal if you’re acne-prone is to avoid thick makeup, sunscreen, or lotion products that might clog your pores—look for that “non-comedogenic” wording on the product packaging.

A note on fungal acne : Fungal acne is a colloquial term for a type of yeast infection that inflames the hair follicles on your skin. The actual name for this condition is either pityrosporum folliculitis or malassezia folliculitis, depending on whom you’re talking to. It causes red bumps and pustules that might look like acne, but don’t usually affect the face. Unlike actual acne, so-called fungal acne is treated with antifungal medications. So if you’re not sure what type of bumps you’re dealing with or your usual acne treatments don’t seem to be helping, talk to a dermatologist to see if you might be dealing with a fungal issue instead.

Azelaic acid: A type of acid synthesized by yeast, barley, and wheat that’s believed to have a gentle exfoliating effect. Research has shown that it’s effective at managing both acne and acne-like bumps that are a common symptom of rosacea. 2 It comes in prescription and over-the-counter forms.

Benzoyl peroxide : Unlike salicylic acid, benzoyl peroxide can kill the type of bacteria that’s often responsible for inflamed acne. That’s why it’s often recommended to use both benzoyl peroxide and salicylic acid to help manage mild to moderate acne. For more severe acne, a retinoid or other prescription treatment may be necessary. Both salicylic acid and benzoyl peroxide can also irritate or dry out skin, so it’s important to also use a moisturizer when you’re using these ingredients.

Chemical exfoliants : You may already be familiar with physical exfoliants such as scrubs and brushes. And while those are perfectly effective at removing dead skin that can clog pores, they’re not exactly gentle. That’s why many dermatologists recommend their patients stick with chemical exfoliants for facial skin, which include both alpha hydroxy acids, or AHAs (such as lactic acid and glycolic acid), and beta hydroxy acids, or BHAs (essentially just salicylic acid). “AHAs are water-soluble and help peel away the top surface of the skin, making it smoother. BHA is oil-soluble and penetrates deeper into the pores to remove dead skin cells and excess sebum,” Dr. Skotnicki says.

Rather than physically scrubbing the dead skin cells off your face, these chemicals break down the bonds between those cells so that you can easily wipe them away. They’re present in all kinds of products, including cleansers, toners, masks, and serums. Just note that you’re essentially using a peel, so you won’t want to apply products containing AHAs or BHAs on the same night as a retinol product to combat acne. “They’re irritating, so using both on the same day can lead to dryness and redness,” points out Dr. Skotnicki.

Niacinamide (see above)

Retinoids (see above)

More on how to treat acne:

• What to Do When Your Skin Is Freaking Out From Retinol
• Why So Many People Swear By Azelaic Acid to Combat Acne and Redness
• 12 Common Face ‘Bumps’ and How to Deal With Them
• How to Get Rid of Blackheads on Your Nose, Chin, and Forehead
• The Acne-Prevention Strategies Glasses-Wearers Need to Know
• Here’s How to Tell If Your Skin-Care Products Are Actually Non-Comedogenic
• Everything You Need to Know About Fungal Acne, Including How to Treat It

For some people, scars are almost a badge of honor or a physical mark that shows you endured an intense event. But others would rather not have them hanging around. And if you’re trying to minimize the appearance of a scar, the first thing to know is that you’ll have to be patient—and especially skeptical.

• Contracture scar: Though uncommon, these painful scars—which cause the skin to tighten—can develop after a large area of skin is damaged or lost (typically due to a burn).
• Depressed (or atrophic) scar: Typically caused by chicken pox and acne, these marks sit below the skin’s surface—usually on facial skin—and have an indented appearance.
• Flat scar (cicatrix): These scars tend to be slightly raised at first, but eventually flatten. They may end up slightly darker or lighter than your skin tone.
• Keloids: These are larger, often dark raised scars that most commonly form after skin is cut—from an injury, surgery incision, or piercing, for example—and are more likely to affect people with darker skin tones.
• Raised (or hypertrophic) scar: Yep, these firm scars rise above the surface of your skin, though they tend to flatten over time.
• Stretch marks: You’re likely pretty familiar with them already because they exist on many bodies, but stretch marks are a type of scar that typically forms when skin grows or shrinks quickly. This could be during pregnancy, weight fluctuations, or any other changes in your body.

Over-the-counter topical scar treatments don’t have a ton of evidence behind them, unfortunately. What does work? Moisturizing—almost to an excessive degree—and time. If that doesn’t help, you should chat with a dermatologist about your other options, which may include prescription topical treatments or laser treatments.

When it comes to dark spots, melasma (a skin condition that involves dark or brown spotting on the face), or other hyperpigmentation concerns, though, you can try brightening ingredients, like vitamin C and hydroquinone. “Just be sure to correctly identify the source of the hyperpigmentation first,” Dr. Hartman says. Inflammation is a major cause of hyperpigmentation, for example, so “it is important to determine the best way to control the inflammation that’s driving the hyperpigmentation in the first place,” according to Dr. Hartman. And that might require a visit to your health care provider to get to the bottom of the inflammation.

Ingredients:

Hydroquinone : Often considered the gold standard of brightening ingredients, hydroquinone decreases the ability of melanocytes, the cells that produce pigment, to produce melanin. It’s available over-the-counter (at concentrations of up to 2%) and via prescription in higher strengths.

Sunscreen : Prevents dark spots from getting darker (see more above). Emerging research suggests that visible light, including light that comes from our devices like phones and laptops, may be a factor in exacerbating hyperpigmentation, especially melasma. That’s where sunscreen comes into play, even if you’re staying inside all day. “If you’re treating hyperpigmentation and not wearing consistent daily sunscreen, you’re getting in your own way and not adequately addressing the problem,” Dr. Hartman says.

Some experts recommend that people trying to manage those issues look for mineral sunscreens, which help block visible light, in addition to other SPF ingredients.

Chemical exfoliants: (see above)

Retinoids: (see above)

Vitamin C: (see above)

Read more about treating skin with scars and discoloration:

• 8 Dark Spot Treatments That Really Work, According to Dermatologists
• Ask a Beauty Editor: How Long Does It Take for Topical Scar Creams to Actually Work?

Dry skin also tends to be sensitive, and dry skin can also be a symptom of skin conditions that make the skin more sensitive, like eczema. So products for dry skin are often suitable for sensitive skin as well—but not always.

If you have sensitive skin (meaning you are prone to irritation or allergic reactions or have a skin condition like eczema, psoriasis, or rosacea), it’s especially important to be aware that products containing things like fragrance chemicals are more likely to cause a reaction. It’s also a good idea to patch test any new product on your inner arm for a day or two before using it all over your face.

Bakuchiol : Bakuchiol is a plant extract that some early research suggests can have a beneficial effect on skin, particularly with regard to managing signs of aging, without irritation. 3 It’s often called a “natural retinol alternative,” although it doesn’t have quite as much evidence behind it. But experts say bakuchiol may be a good option—especially if your skin is too sensitive for retinoids. If your skin can’t tolerate retinol at 1%, try bakuchiol, Dr. Skotnicki says. “It’s been shown to have similar effectiveness to retinol at 0.5%, with less irritation,” she adds.

Colloidal oatmeal : Colloidal oatmeal is made from grinding oats and mixing them with water or other liquid, which creates a mixture that can provide a soothing, protective barrier on the skin. Experts recommend it specifically for dry and sensitive skin, including skin that’s actively irritated, in which the skin’s natural barrier may need some extra help.

Hyaluronic acid : Hyaluronic acid is found naturally in the skin and acts as a humectant, meaning it can draw moisture into the skin; products with these molecules allow moisture to bind to the skin without feeling greasy or heavy.

Squalane oil : Squalane is a light moisturizing oil that mimics a component of sebum, the oily substance our skin produces. There is limited research on the effect of topical squalane on skin, but in general, it acts like an emollient when applied, which means that it can squeeze into the spaces between skin cells and make your face feel smoother and more moisturized without being too heavy or occlusive. 4

Ceramides: (see above)

Niacinamide: (see above)

Read more on treating sensitive skin:

• 7 Derm-Approved Tips to Make Life With Sensitive Skin a Little Bit Easier
• 9 Hyaluronic Acid Products Dermatologists Always Recommend for Hydrated Skin
• What the Heck Is Squalane Oil and Why Is It in All My Skin-Care Products Now?
• Centella Asiatica: What It Can Really Do for People With Sensitive Skin
• Here’s What Niacinamide Can—And Can’t—Do for Your Skin
• 19 Gentle Exfoliators Dermatologists Recommend for Sensitive Skin
• Meet PHAs, the Chemical Exfoliants Your Sensitive Skin Might Just Love

There are so many kinds of skin-care products on the market, it’s hard to know what works and what’s hype. What else should I know about skin-care ingredients before I get started?

As we mentioned above, cosmetic skin-care ingredients don’t go through FDA testing before they hit the market, so we don’t have data on how effective or safe each over-the-counter product is. Many companies make claims about their products based on the ingredients that are in the product, which may or may not be similar to the ingredients used in scientific research.

Basically, unless you’re using a prescription treatment, it’s tough to know what you’re actually getting when, so it always pays to weigh the potential risks and benefits before putting something new on your skin. Your best bet is to spend money on products containing active ingredients with the most promising research behind them.

In general, the risks include irritation, allergic reactions, or simply wasting time and money. But if you have sensitive skin or a skin condition, you’re more likely to experience those kinds of adverse reactions, so you’ll want to be more careful when trying new products, especially trendy new ingredients that don’t have a lot of solid evidence for their claims. If in doubt, you can always check with a dermatologist.

More about trendy skin-care ingredients and the actual science behind them:

• What Tea Tree Oil Can and Can’t Do for Your Skin
• Can Any Skin-Care Products Actually ‘Detox’ Your Face?
• What You Should Know Before Using a Trendy New Face Oil
• I Washed My Face With Manuka Honey for a Week—Here’s What Happened
• Does Face Mist Actually Do Anything for Your Skin?
• Do Collagen Creams and Supplements Actually Do Anything?
• Is There Literally Any Reason for CBD to Be in Your Skin-Care Products?
• What’s the Actual Deal With Skin Toners and Essences?
• Caffeine Doesn’t Really ‘Wake Up’ Your Skin—But It Might Do Something Else
• Your Vulva Doesn’t Need Skin-Care Products
• Here’s What Dry Brushing Your Skin Actually Does—And Doesn’t Do

Is there anything in particular I need to know about caring for my skin of color?

People with melanin-rich skin are generally more susceptible to skin issues involving hyperpigmentation, such as melasma and post-acne dark spots. You may also be more likely to develop scarring or hyperpigmentation after inflammatory skin issues, like acne, psoriasis, or eczema.

That can be frustrating because treating pigmentation concerns in darker skin is often somewhat challenging with treatments that are commonly used on white skin, like laser treatments . But laser treatment techniques have advanced a lot in recent years, and in the hands of an experienced practitioner they can be safely used in patients with skin of color. Additionally, topical treatments containing things like hydroquinone and vitamin C can help too. But whatever you do, know that treating hyperpigmentation takes time—possibly six months to a year.

There’s also a prevalent myth that people with darker skin don’t need to wear sunscreen —this is definitely not true! The sun can still cause damage even if you’re not getting sunburned. And that damage can both lead to skin cancer and exacerbate hyperpigmentation. When shopping for sunscreen, don’t necessarily avoid mineral sunscreen if you have a deeper skin tone. “There are many great mineral sunscreen options that don’t leave a white cast behind on darker skin tones,” Dr. Hartman says. “I like the protection that they confer and the significant reduction in occurrences of irritation.”

Versed Guards Up Daily Mineral Sunscreen Broad Spectrum SPF 35

Sunscreen isn’t the only thing you should keep in your skin-cancer-preventing toolbox. People with darker skin tones are more likely to be diagnosed with certain types of melanoma at later stages than those with lighter skin. That’s partially because medical textbooks and clinical trials have historically centered on light skin, resulting in a lower public awareness of the risk of skin cancer for people of color. But also, a rare form of melanoma called acral-lentiginous melanoma is more prevalent in people with deeper skin tones. It’s more likely to appear in areas that get little sun and that you wouldn’t normally check, like the palms, bottoms of the feet, and under fingernails. It’s important to check your skin regularly, particularly more hidden areas like the top of your head, nails, and the bottom of your feet for dark spots or sores that won’t heal.

If you have any questions about how to care for your skin of color or about managing an issue like melasma, your best bet is to talk to a dermatologist.

More on caring for skin of color:

• 5 Things People of Color Should Know About Taking Care of Their Skin
• Why Are Black People Less Likely to Get Melanoma but More Likely to Die From It?
• I Desperately Tried to Find a ‘Cure’ for My Undereye Circles—Until I Realized They’re Genetic
• What You Should Know About Melasma, Those Random Dark Spots on Your Face

I’m pregnant. What products can I use and what should I avoid?

When you’re pregnant, you might notice many changes in your skin, such as pregnancy-related acne, a hormonal effect of excess oil production, or, even more commonly, hyperpigmentation. Melasma affects 15 to 50% of pregnant people. “Hormones seen with pregnancy, birth control use, menopause, and hormone replacement therapy may stimulate the pigment-producing cells in the skin called melanocytes to over-produce melanin, resulting in the condition,” Adeline Kikam, D.O. , board-certified dermatologist, tells SELF.

Before you treat any skin concerns related to pregnancy, it’s important to check the ingredients on product labels. If you’re pregnant or breastfeeding, you may need to temporarily stop using certain products, especially certain acne products. According to the American Academy of Dermatology (AAD), pregnant people should definitely avoid using retinoids including isotretinoin, tretinoin, tazarotene, spironolactone, and adapalene. “They can affect the development of the ectoderm [the outermost layer of tissue] in the fetus, which includes skin,” Dr. Skotnicki says, and they may pose a risk of birth defects. 4 You should also be careful about certain antibiotics, such as doxycycline–it belongs to a class of antibiotics, tetracyclines, that have been shown to negatively affect fetal bone and teeth development. 5 Depending on your doctor’s recommendations, you may also need to limit benzoyl peroxide and salicylic acid. It’s been confirmed that they’re generally safe in low concentrations during pregnancy, but the research is limited, Dr. Skotnicki says.

You should also be cautious about brightening ingredients— particularly hydroquinone , which hasn’t been studied enough in pregnant people and has the potential to affect fetal development, as you may absorb about 35 to 45% of topical hydroquinone into your bloodstream. 7 One other skin-care ingredient to avoid is CBD, mostly because, again, there haven’t been enough studies on its effects on pregnant people, Dr. Skotnicki says.

In general, though, we don’t have a ton of information about how these (and, honestly, most) ingredients affect pregnant people, the AAD says . Many of these recommendations are based on an absence of conclusive evidence that they are safe rather than having evidence that they’re definitely harmful.

Above all it’s important to check in with your doctor or dermatologist before using something on your skin when pregnant or breastfeeding because they can assess your individual skin situation and help you figure out what makes sense for you.

More on caring for your skin while you’re pregnant:

• How to Safely Treat Your Postpartum Acne
• 5 Acne Products That Are Safe to Use While Pregnant or Trying to Conceive
• 17 Skin-Care and Beauty Products People Loved When They Were Pregnant

What if I have a specific medical condition that affects my skin?

If you have a skin condition (such as rosacea, psoriasis, eczema, or severe acne) or any condition that affects your skin, it’s important for you to see a dermatologist and make your skin-care decisions with their input. Not only is your skin likely to be more sensitive to skin-care products, but you also don’t want to do anything that might exacerbate the underlying condition.

Plus if you’re trying to manage that condition, you can only go so far with over-the-counter products. Sometimes they can get the job done (like using a drugstore cleanser containing salicylic acid for mild acne), but you want to be sure that you’re not overlooking another option that may be more effective, like a prescription retinoid.

So over-the-counter products aren’t off-limits for you entirely, but you will want to approach them with caution. It may be wise for you to do patch tests (putting a small amount of a new product on your inner arm for a day or two) before using anything new, especially something that you saw on TikTok, Dr. Hartman says. If you’re able, it would be even wiser to have a dermatologist perform a formal test in their office to see which ingredients you’re likely to be sensitive to so that you’re not exacerbating the skin condition with too much experimentation on your own. With the right approach, skin care can be an effective (and maybe even fun!) way to manage the symptoms of your condition.

More on caring for your skin if you have a medical condition:

• What Can Centella Asiatica Really Do for Red, Dry, Sensitive Skin?
• How to Tell if Your ‘Acne’ Might Actually Be Rosacea
• Here’s How Stress Actually Impacts Your Skin
• How to Tell the Difference Between Psoriasis and Eczema
• I Have Keratosis Pilaris. These 8 Products Actually Smoothed My Skin

What about “clean” beauty? How do I make sure everything in my skin-care routine is safe?

Considering how little the FDA is involved in regulating cosmetic skin-care ingredients, it’s understandable that you’d want to do whatever you can to make sure you’re only putting the safest ingredients possible on your skin.

But words like “clean” and “natural” on skin-care products are more buzzwords than anything else . These terms don’t have agreed-upon definitions and aren’t regulated by the FDA, so any company can define clean beauty however it wants and give itself that label. There is no formal definition or nationally recognized or accepted standards when it comes to those claims,” Dr. Kikam says. If you’re concerned about certain ingredients like “fragrance,” parabens, or phthalates because they can be irritating to sensitive skin, your best bet is to avoid products that list those ingredients on the label, she advises. ( Research from the National Eczema Association shows that fragrance chemicals cause allergic reactions in 8 to 15% of people with contact dermatitis, and reactions to parabens and phthalates seem to be less common but still possible). 8 9

It’s also important to remember that just because something is natural doesn’t mean it’s safe. In fact, natural herbal and botanical ingredients are frequently irritants and allergens for those with sensitive skin. And our health concerns about certain chemicals in makeup and skin-care products are often overblown .

Moreover, herbal and botanical ingredients (which are still chemicals, BTW) aren’t necessarily analogous to the compounds tested in clinical trials. For instance, rose hip contains vitamin A but isn’t the same thing as retinol or retinoic acid, so you don’t necessarily know how much vitamin A you’re putting on your face or what kinds of effects you can expect.

Again, we recommend opting for products that contain ingredients we know the most about. And if you’re not sure if something is right for your skin, talk to a dermatologist.

More on what “clean” and “natural” skin care really mean:

• What the Research Says About 10 Controversial Cosmetics Ingredients
• A Beginner’s Guide to Vegan and Cruelty-Free Beauty and Skin Care

I’m really excited to get started. Which products do you like best?

Well, first off we’d suggest checking out the 2021 SELF Healthy Beauty Awards winners . These products were selected with the help of dermatologists, a well as reviews from 65 judges with different skin types, skin conditions, and skin concerns.

Definitely also take a look at these stories on finding the mainstays of your skin-care regimen: cleanser , moisturizer , and sunscreen .

If you’re interested in looking for products containing specific active ingredients or products that can help address certain skin concerns, check out these handy articles:

• The 22 Best Eye Creams, According to Dermatologists
• The 29 Best Skin-Care Products for Aging Skin—That Dermatologists Actually Use
• 13 Dermatologist-Approved Moisturizers That Your Dry Skin Will Love
• The 20 Best Derm-Approved Moisturizers for Acne-Prone Skin
• The Best Acne Spot Treatments Dermatologists Swear By
• I’m a Beauty Editor With Sensitive Skin and These Are the 11 Holy Grail Skin-Care Products I Use (Almost) Every Day
• The 17 Best Acne Treatments, According to Dermatologists
• 7 Over-the-Counter Retinol Serums and Creams Dermatologists Highly Recommend
• 8 Niacinamide Products Dermatologists Absolutely Swear By
• The Best Facial Sunscreens on Amazon, According to Customer Reviews
• 16 Skin-Care Products Women With Rosacea Love
• 16 Skin-Care Products Women With Eczema Love

We hope that this guide has helped you demystify the world of skin care. Be sure to check all our skin-care coverage here .

• Journal of the American Academy of Dermatology , Topical niacinamide-containing product reduces facial skin sallowness (yellowing)
• MedlinePlus , Azelaic Acid Topical
• British Journal of Dermatology , Prospective, randomized, double-blind assessment of topical bakuchiol and retinol for facial photoageing
• Indian Journal of Dermatology , Moisturizers: The Slipper Road
• Canadian Family Physician , Safety of skin care products during pregnancy
• Expert Opinion on Drug Safety , Revisiting doxycycline in pregnancy and early childhood–time to rebuild its reputation?
• StatPearls , Hydroquinone
• FDA , Parabens in Cosmetics
• Environment International , Phthalate exposure and allergic diseases: Review of epidemiological and experimental evidence

SELF does not provide medical advice, diagnosis, or treatment. Any information published on this website or by this brand is not intended as a substitute for medical advice, and you should not take any action before consulting with a healthcare professional.

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Fortify your moisture barrier with these three products for stronger, more radiant skin.

Take the Renée Rouleau Skin Type Quiz to find out which of the nine skin types you are!

• ABOUT About Renée About the Products History Media Inquiries Contact

Find your skin type

• Discoloration
• Cystic Acne
• Sensitive Skin
• Sun Protection
• Day & Night
• Myths & Mistakes
• Special Occasions
• Health & Wellness
• Nutrition & Exercise
• Devices and Tools
• Estheticians
• Ingredients
• Professional Treatments

Why I Love Being an Esthetician

I began my esthetics career in 1987, just a few months after graduating from High School. I was lucky in that I always knew what I wanted to do. My grandmother was a hairdresser and owned her own beauty salon, so I truly believe the career of helping people look and feel beautiful was in my genes.  (Read why my grandmother was my beauty role model .)

After more than 20 years of working with skin hands-on, I still love being an esthetician.  Here’s why:

• It’s a very emotionally rewarding profession. Making people look good also makes them feel good; which in turn, makes me feel good. It’s happiness for all!
• I’m never bored. Every client has different concerns with their skin, so it’s definitely not “same old, same old”. I love treating all aspects from acne to rosacea , and brown spots to wrinkles . No two skins are alike, and that makes it very exciting. I’ve always wondered how skin care companies can say their line is “suitable for all skin types” when all skins have different needs. Check out my nine skin types …
• With all of the advancements in skin care, there is much to be learned. I have an intense passion for learning. Between industry magazines, books, trade shows, webinars, blogs, classes and websites, the opportunities to learn are endless. I am truly a believer that in all professions, you must stay up to date with what’s going on in the industry to be at the top of your game. The skin care industry is fast moving with advances, so continuing education is a must.
• Increased awareness of esthetics brings respect to this profession . When I started my career in 1987, nobody knew what an esthetician was. “You’re a what? Isn’t that when you put people to sleep before surgery?” No, that’s an anesthesiologist ! Back then, doctors absolutely frowned upon facials and estheticians. But now, they are FINALLY embracing the seriousness of skincare, and many estheticians work from doctor’s offices.  Plus, the increasing demand for people wanting younger-looking skin has turned esthetics into a well-respected profession. Although this is a new twist in US history, in France, it has been that way for many, many decades. (Read my French Skin Care Investigation .)
• The power of touch is transforming . Since the start of my career in esthetics, I have volunteered my time and skills at women’s shelters to give facials to those who have been affected by domestic violence. (I myself was in a bad relationship early on, so I vowed from that day forward that I would help in any way I could.) When these women are abused, they learn that ‘touch’ means anger and violence. Giving them a facial shows that touch can come from a loving and caring place, and they need to learn to trust touch again. The result of the facial is they are looking better.  When they look better, they feel better.  When they feel better, self esteem increases, and that is the key for women to be empowered to stay out of violent situations. I could go on and on about the amazing experiences I have had with these women (I cry just thinking about them) but one thing I know for sure—a facial gives far more benefit than just to the skin.
• I love what I do, and it shows . I am so lucky that I have found a career that I love so much.  I really am doing my part to create positive change in the world—one face at a time. From sharing daily skin care tips and expert advice on my blog , Twitter , Facebook and monthly emails (sign up to receive emails here ), I love to share my knowledge and help others. Being an esthetician isn’t only about giving facial treatments and selling skin care products, it’s about helping create change and therefore lives.

With all of the reasons to love this profession, it’s no wonder I did a Google search one day on jobs and ‘esthetician’ came up as having one of the highest job satisfaction rates!

I have truly enjoyed every minute of my career as an esthetician, and I feel like I’m just getting warmed up.

Read: The pros and cons of being an esthetician.

Read more about skin care expert, Renée Rouleau .

Celebrity Esthetician & Skincare Expert As an esthetician trained in cosmetic chemistry, Renée Rouleau has spent 30 years researching skin, educating her audience, and building an award-winning line of products. Her hands-on experience as an esthetician and trusted skin care expert has created a real-world solution — products that are formulated for nine different types of skin so your face will get exactly what it needs to look and feel its best. Trusted by celebrities, editors, bloggers, and skincare obsessives around the globe, her vast real-world knowledge and constant research are why Marie Claire calls her “the most passionate skin practitioner we know.”

Disclaimer: Content found on www.ReneeRouleau.com and Blog.ReneeRouleau.com, including text, images, audio, or other formats were created for informational purposes only. The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or another qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website or blog.

Related Blog Posts

Hi Renee, Thanks for being there for us. I’m an Estie the making. I’m here in SoCal training and working p/t as an attorney. I love the way treating clients feels. I’m am interested in traveling and offering my services globally and creating a skincare line.

Thank you for being an inspiration!

Posted By: Marci  |  July 9, 2016

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Great skin starts with knowing your skin type.

Skin Care Essay Example

When starting into the skin care  world, the one thing you should always remember is less is more. You don’t need a 9 step routine, especially in the morning. The 2 main purposes of a morning skin care  routine are 1. Wash off all nighttime products and 2. Protect your skin for the day. You should also remember that not one product suits everybody. The state of your skin will depend on the products you should use. Here are the key steps in a morning skin care  routine for someone with dry or oily skin.

The first step to a good skin care  routine is always a cleanser. In the morning a gentle cleanser is best, especially for dry skin. If your skin is extremely dry, cleansing with water would work fine. Follow the directions on the back of the bottle on how to apply the cleanser, then gently wash it off with water or a washcloth.

Next you should treat your skin, think of something you would like to change within your skin. As a person with dry skin you may want to add moisture to your skin. A great product for this is a hyaluronic acid serum. Hyaluronic takes moisture from the air and directs it to your skin. In a serum form, hyaluronic acid can be very gentle and effective.

Now you should use a moisturizer. Something light can suffice in the morning, especially if you're using sunscreen.

The final step is sunscreen. Now as I said this is a basic morning routine, but no matter how many products you use, you must always use sunscreen and it should always be the last step. No matter how good a skin care  routine is, it’s nothing without sunscreen.

Similar to a dry skin routine, the first step is a cleanser. However with oily skin, using only water is not as beneficial or effective to treating any problems that result from oiliness. A gentle or treatment cleanser is best for the morning, just always remember that the point of a morning cleanse is to take off night time products. 

Next you should use a treatment. A niacinamide or vitamin C serum is definitely the way to go. They get rid of any dark spots and reduce oiliness.

Now you should use a spot treatment. With oiliness usually comes clogged pores which cause acne. A spot treatment is an effective way to only treat a particular areo on the face. Look for products with salicylic acid or benzoyl peroxide for an effective treatment.

Finally, finish with sunscreen. Use one that is oil free and lightweight, this will decrease the feeling of oil on your face. You could also use a sunscreen, moisturizer combination product if that is what feels best.

As for normal skin, you have it lucky. You can basically use whatever products you want. You also have the luxury of treating other concerns such as fine lines and dark circles because you have no larger issues. Although you are more ‘free’ when it comes to choosing products, make sure you still use a minimalist routine, because when it comes to skin care , less is more.

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Home — Essay Samples — Nursing & Health — Skin — Structure and Function of the Skin

Structure and Function of The Skin

• Categories: Body Skin

About this sample

Words: 381 |

Published: Jan 15, 2019

Words: 381 | Page: 1 | 2 min read

Works Cited

• Wolff, K., Johnson, R. A., Saavedra, A. P., & Roh, E. K. (2017). Fitzpatrick's Color Atlas and Synopsis of Clinical Dermatology (8th ed.). McGraw-Hill Education.
• Kumar, V., Abbas, A. K., Aster, J. C., & Robbins, S. L. (2019). Robbins Basic Pathology (10th ed.). Elsevier.
• James, W. D., Berger, T. G., & Elston, D. M. (2020). Andrews' Diseases of the Skin: Clinical Dermatology (13th ed.). Elsevier.
• Rigel, D. S., Robinson, J. K., & Ross, M. I. (2019). Cancer of the Skin. In K. D. Mann, L. E. Benveniste, J. S. Cooper, A. N. Hata, & S. G. Patel (Eds.), Abeloff's Clinical Oncology (6th ed., pp. 1799-1825). Elsevier.
• National Cancer Institute. (2021). Skin Cancer (Including Melanoma)—Patient Version. https://www.cancer.gov/types/skin
• Kim, R. H., Armstrong, A. W., & Harpole, D. H. (2016). Cutaneous Melanoma. In C. A. Pautler & R. T. Chung (Eds.), Current Diagnosis & Treatment: Gastroenterology, Hepatology, & Endoscopy (3rd ed., pp. 1217-1236). McGraw-Hill Education.
• Gloster Jr, H. M., & Neal, K. (2006). Skin Cancer in Skin of Color. Journal of the American Academy of Dermatology, 55(5), 741-760. https://doi.org/10.1016/j.jaad.2005.08.063
• Wong, S. L., Balch, C. M., & Hurley, P. (2018). Surgical Treatment of Primary Melanoma. In K. D. Mann, L. E. Benveniste, J. S. Cooper, A. N. Hata, & S. G. Patel (Eds.), Abeloff's Clinical Oncology (6th ed., pp. 1839-1855). Elsevier.
• Seyed, J., & Aghdasi, M. (2017). Anatomy, Skin (Integument), Epidermis. In StatPearls [Internet]. StatPearls Publishing.
• Holliday, R. (2019). Anatomy, Skin (Integument), Dermis. In StatPearls [Internet]. StatPearls Publishing.

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Skin-to-Skin Care to a Newborn Infant Research Paper

Introduction, methodology.

Qualitative research may be crucial to expanding the existing breadth of post-delivery care knowledge. Thus, the paper “Parental experiences of providing skin-to-skin care to their newborn infant” by Anderzen-Carlsson, Lamy, and Eriksson (2014) aims to describe parents’ various experiences with skin-to-skin contact (SSC). As such, the article is vital for understanding the psychological processes of both participating parties and remains relevant to increasing the quality of provided post-partum care.

The study’s impeccable methodology defends the quality of its results. The researchers used a data extraction method to obtain information about parents’ subjective experiences (Anderzen-Carlsson et al., 2014). A qualitative approach seems to be most beneficial for this type of research since the article’s objective links with analysing the sentiment felt by mothers and fathers during SSC, rather than a clear hypothesis (Cristancho, Goldszmidt, Lingard, & Watling, 2018; McCusker & Gunaydin, 2015).

Anderzen-Carlsson et al. (2014) justify the research design under a formulate-extract-appraise methodology, choosing articles with a solely qualitative methodological base using both systematic and manual searching techniques to select studies from four databases. Thus, data was collected in a way that reflected the objective of the research issue.

The conducted analysis allows making a statement about the results’ integrity. The primary means of research was meta-data analysis using NVivo computer software, a reliable program that facilitates the research process, which analysed relevant original quotations and helped categorise the uplifted data into 19 distinct categories (Anderzen-Carlsson et al., 2014; Zamawe, 2015). Potential bias was removed by having multiple researchers appraise articles using an impartial Primary Research Appraisal Form, and the initial literature searches were performed twice to secure the result’s actuality (Anderzen-Carlsson et al., 2014).

Anderzen-Carlsson et al. (2014) tackle each of the 19 defined categories in detail, presenting a definite conclusion regarding the research question regarding the various psychological states of parents post-delivery and during SSC. It is important to note that the researchers did not explicitly discuss any ethical issues raised by the study.

The research attains its goals, and it could be worth continuing from a viewpoint that deals with parental experiences directly or relates to solely paternal experiences. The discussion tackles the range of experienced emotions and their implications for post-partum care, as well as the limitations of their research, such as an overabundance of mothers compared to fathers. Therefore, the paper successfully refines the existing data on the topic of SSC’s effect on parents post-delivery.

Anderzen-Carlsson, A., Lamy, Z. C., & Eriksson, M. (2014). Parental experiences of providing skin-to-skin care to their newborn infant – Part 1: A qualitative systematic review. International Journal of Qualitative Studies on Health and Well-Being , 9 (1), 1-22. Web.

Cristancho, S. M., Goldszmidt, M., Lingard, L., & Watling, C. (2018). Qualitative research essentials for medical education. Singapore Medical Journal , 59 (12), 622-627. Web.

McCusker, K., & Gunaydin, S. (2015). Research using qualitative, quantitative or mixed methods and choice based on the research. Perfusion , 30 (7), 1-6. Web.

Zamawe, F. C. (2015). The implication of using NVivo software in qualitative data analysis: Evidence-based reflections. Malawi Medical Journal , 27 (1), 13-15. Web.

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IvyPanda. (2021, August 9). Skin-to-Skin Care to a Newborn Infant. https://ivypanda.com/essays/skin-to-skin-care-to-a-newborn-infant/

"Skin-to-Skin Care to a Newborn Infant." IvyPanda , 9 Aug. 2021, ivypanda.com/essays/skin-to-skin-care-to-a-newborn-infant/.

IvyPanda . (2021) 'Skin-to-Skin Care to a Newborn Infant'. 9 August.

IvyPanda . 2021. "Skin-to-Skin Care to a Newborn Infant." August 9, 2021. https://ivypanda.com/essays/skin-to-skin-care-to-a-newborn-infant/.

1. IvyPanda . "Skin-to-Skin Care to a Newborn Infant." August 9, 2021. https://ivypanda.com/essays/skin-to-skin-care-to-a-newborn-infant/.

Bibliography

IvyPanda . "Skin-to-Skin Care to a Newborn Infant." August 9, 2021. https://ivypanda.com/essays/skin-to-skin-care-to-a-newborn-infant/.

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L'Occitane blocks model from registering skin care trademark

Alice Taticchi’s Arboria Skin Care trademark was considered too similar to the beauty group’s Erborian brand

L’Occitane has successfully stopped an Italian model from registering a trademark similar to its Erborian brand. 

Alice Taticchi was prevented from registering her Arboria Skin Care trademark by the Fifth Board of Appeal of the European Union Intellectual Property Office (EUIPO). 

According to the board, potential customers were likely to confuse the two brands due to “strong commonalities, both visually and aurally”. 

Taticchi has been embroiled in a dispute with L’Occitane for more than two years. 

The former Miss World beauty pageant contestant applied to register Arboria in late 2021.

L’Occitane challenged the application in 2022, a position supported the following year by EUIPO’s opposition division, which concluded that there was a likelihood of confusion between Arboria and Erborian. 

Taticchi appealed, arguing that Erborian alludes to “herbs of the orient”, while Arboria was a reference to the word “arboreal”, relating to trees.

However the board ruled that a vast majority of consumers would consider both names to be “meaningless fantasy terms”.

The trademarks in the suit are French trademark number 3457744, international trademark number 1584189, and EU trademark number 018567433.

Erborian, which was co-founded by Katalin Berenyi and Hojung Lee ​​in 2006, has been a part of L’Occitane’s portfolio since 2012.  

It uses herbs from the traditional Korean pharmacopoeia to make products that bridge the gap between skin care and make-up. 

Arboria’s product line, meanwhile, comprises six skus which are based on aloe vera from Salento, located in the ‘heel’ of Italy. 

• L'Occitane

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The Pivotal Role of HIPAA in Modern Healthcare: Protecting Privacy while Fueling Innovation

This essay about the Health Insurance Portability and Accountability Act (HIPAA) of 1996 discusses its crucial role in the American healthcare system. It outlines how HIPAA serves as a foundational framework that protects patient privacy and fosters trust between patients and providers by ensuring sensitive health information is shared and used responsibly. The essay also examines HIPAA’s influence on technological innovation, particularly in how it drives the development of secure health technologies like electronic health records and telemedicine platforms. Additionally, it explores HIPAA’s impact across various sectors beyond traditional healthcare, including technology companies that handle health data. Challenges related to compliance and the need for continuous adaptation of the regulations to accommodate new technologies are also discussed. Overall, the essay underscores HIPAA’s dual role in protecting patient information while supporting healthcare improvements through technology.

How it works

The Health Insurance Portability and Accountability Act (HIPAA) of 1996 stands as a watershed in the annals of American healthcare, setting the precedent for patient privacy and data protection. Its profound influence is felt not only in the realm of healthcare but also in the seamless integration of technology within this sector, creating a landscape where patient trust and innovative medical technology thrive together.

HIPAA: A Beacon of Trust in Healthcare

Originally conceived to enhance healthcare coverage for working Americans and their families, HIPAA quickly evolved beyond this initial purpose.

Its most enduring legacy is perhaps the Privacy Rule, which safeguards personal health information, ensuring that it’s handled with the utmost discretion and only shared under circumstances that directly benefit patient care.

This rule forms the backbone of patient confidence in the healthcare system. In a world increasingly driven by data, the assurance that personal health information is protected is not just comforting—it’s essential. Patients are more likely to be forthcoming about their health issues when they trust that their sensitive information won’t be misused. This openness is crucial for accurate diagnosis and effective treatment, directly impacting patient health outcomes.

Fostering Innovation in Healthcare Technology

Alongside its privacy mandates, HIPAA has also spurred a culture of innovation, particularly in relation to the handling of electronic health records (EHRs). The HIPAA Security Rule was introduced to manage the protection of electronic personal health information (ePHI), which includes directives for physical, administrative, and technical safeguards.

These requirements have pushed technology vendors to pioneer new solutions that comply with HIPAA’s stringent standards. From advanced encryption methods to secure patient portals and telemedicine services, technology under HIPAA has had to evolve. This evolution has not only made patient data more secure but has also made healthcare more accessible and efficient. For instance, secure telemedicine platforms, which became particularly vital during the COVID-19 pandemic, are a direct outcome of the need to comply with HIPAA while providing essential services.

HIPAA’s Extended Influence Across Sectors

HIPAA’s reach extends beyond traditional healthcare settings, affecting a wide array of industries that interact with health data. It influences how health apps, wearable devices, and even genetic testing services manage and protect user data. Companies operating in these spaces must design their products and services with HIPAA compliance in mind, integrating data protection from the initial stages of development.

This has led to an environment where patient data protection is paramount, regardless of whether the data is handled in a hospital, through an insurance claim, or via a health management app. The ramifications for data security protocols across these diverse platforms are profound, creating a unified standard that protects individuals’ privacy across the board.

Challenges and Continuous Adaptation

Despite its widespread acceptance and the robust framework it provides, HIPAA also presents challenges. The regulations can be complex and onerous, requiring continuous education and vigilance to ensure compliance. Healthcare providers and their business associates must stay informed about the latest changes to HIPAA regulations and adapt their practices accordingly.

Moreover, as technology continues to advance, HIPAA itself must adapt. The rise of technologies such as artificial intelligence and machine learning in healthcare presents new challenges for maintaining privacy while harnessing these tools for better patient care. Legislators and healthcare leaders must work together to ensure that HIPAA evolves in a way that both protects patient privacy and facilitates the ethical use of new technologies.

Enhancing the Healthcare Experience

Ultimately, the strength of HIPAA lies in its dual role: protecting patient information while enabling the safe use of that data to improve healthcare outcomes. The act not only reassures patients about the security of their information but also underpins the modern healthcare experience, which increasingly relies on digital and remote technologies.

For patients, the impact of HIPAA is most felt in their interactions with healthcare providers. Knowing their data are protected, patients can engage more fully and openly in their healthcare journeys. This can lead to better healthcare experiences and outcomes, thanks to a system that respects their privacy and utilizes their data responsibly to tailor treatments and services.

In the grand narrative of healthcare, HIPAA occupies a central role, championing the cause of privacy while fostering an ecosystem ripe for technological advancement. Its balanced approach to patient data protection and utilization has made it a model of regulatory success. As the digital landscape evolves, the principles upheld by HIPAA will continue to serve as a guiding light, ensuring that healthcare innovation moves forward without compromising the privacy and trust that patients place in the system.

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The Pivotal Role of HIPAA in Modern Healthcare: Protecting Privacy While Fueling Innovation. (2024, May 21). Retrieved from https://papersowl.com/examples/the-pivotal-role-of-hipaa-in-modern-healthcare-protecting-privacy-while-fueling-innovation/

"The Pivotal Role of HIPAA in Modern Healthcare: Protecting Privacy While Fueling Innovation." PapersOwl.com , 21 May 2024, https://papersowl.com/examples/the-pivotal-role-of-hipaa-in-modern-healthcare-protecting-privacy-while-fueling-innovation/

PapersOwl.com. (2024). The Pivotal Role of HIPAA in Modern Healthcare: Protecting Privacy While Fueling Innovation . [Online]. Available at: https://papersowl.com/examples/the-pivotal-role-of-hipaa-in-modern-healthcare-protecting-privacy-while-fueling-innovation/ [Accessed: 22 May. 2024]

"The Pivotal Role of HIPAA in Modern Healthcare: Protecting Privacy While Fueling Innovation." PapersOwl.com, May 21, 2024. Accessed May 22, 2024. https://papersowl.com/examples/the-pivotal-role-of-hipaa-in-modern-healthcare-protecting-privacy-while-fueling-innovation/

"The Pivotal Role of HIPAA in Modern Healthcare: Protecting Privacy While Fueling Innovation," PapersOwl.com , 21-May-2024. [Online]. Available: https://papersowl.com/examples/the-pivotal-role-of-hipaa-in-modern-healthcare-protecting-privacy-while-fueling-innovation/. [Accessed: 22-May-2024]

PapersOwl.com. (2024). The Pivotal Role of HIPAA in Modern Healthcare: Protecting Privacy While Fueling Innovation . [Online]. Available at: https://papersowl.com/examples/the-pivotal-role-of-hipaa-in-modern-healthcare-protecting-privacy-while-fueling-innovation/ [Accessed: 22-May-2024]

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The 5 Skin and Haircare Products Kate Love Can’t Do Without

Martha zaytoun | may 20, 2024.

Locking down a solid skin and haircare routine is imperative. This is particularly true as summer approaches. With hotter weather and higher UV indexes, our skin—and especially our facial skin—needs greater attention.

Summer is only weeks away, meaning model Kate Love’s latest skincare video couldn’t have been better timed. In the reel, she shared the five skin and haircare products that she “used until the last drop.” In other words, these are her all-time recommendations.

Given that the model spends much of her time in Miami, where she lives with her husband, NBA player Kevin Love, and their daughter, Love is accustomed to summers under a strong sun. Here are the five products that keep her skin and hair healthy, hydrated and glowing year-round.

Minute Media may earn a small commission from your purchase at the following links.

Bonjout Beauty LE BALM , $120 ( bonjoutbeauty.com )

Love uses this restorative and regenerative serum on her face every morning and night. The serum promises deep nourishment and skin barrier repair.

Wander Beauty On-the-Glow Blush and Illuminator , $38 ( wanderbeauty.com )

This on-the-go product from Wander Beauty doubles as both a blush and an illuminator. Love keeps the product—designed for cheeks, lips, eyes and body—in her “purse at all times.”

U Beauty The BARRIER Bioactive Treatment , $198 ( ubeauty.com )

Made with bioactive marine ingredients, this overnight serum is designed to boost your skin’s moisture at the same time that it softens and strengthens. Love puts it on top of her other skincare products both at night and in the morning.

Oribe Après Beach Wave and Shine Spray , $46 ( oribe.com )

The one hair product in the lineup, this pick from Oribe is a good one. According to the model, she and her husband both use the spray to achieve “a little shine and a little finish,” without the crunch that typically accompanies a hairspray.

View this post on Instagram A post shared by K A T E L O V E (@katelove)

The last product that Love can’t do without is Skin Medicinal’s prescription-grade retinol . Unlike her other recommendations, this one can’t be bought online. But Love promises that the product—which has made her skin better than ever—is worth the trip to the dermatologist to get a prescription.

MARTHA ZAYTOUN

Martha Zaytoun is a Lifestyle & Trending News writer for SI Swimsuit. Before joining the team, Martha worked on the editorial board of the University of Notre Dame’s student magazine and on the editorial team at Chapel Hill, Durham and Chatham Magazines in North Carolina. When not working, Martha loves to watercolor and oil paint, run or water ski. She is a graduate of the University of Notre Dame and a huge Fighting Irish fan.