J. Cosmet. Sci., 67, 185–203 (May/June 2016) 185 Effects of season on stratum corneum barrier function and skin biomarkers KARL SHIQING WEI, CHING STELLA, KENNETH R. WEHMEYER, JEREMY CHRISTMAN, AMY ALTEMEIER, RUSSELL SPRUELL, ROHAN L. WIMALASENA, GINA M. FADAYEL, RAYMOND A. REILMAN, SAFA MOTLAGH, PETER J. STOFFOLANO, KATHLEEN BENZING, and R. RANDALL WICKETT, The Procter & Gamble Company, Cincinnati, OH (K.S.W., C.S., K.R.W., J.C., A.A., R.S.L., R.L.W., G.M.F., R.A.R., S.M., P.J.S., K.B.) and James L. Winkle College of Pharmacy, Cincinnati, OH (R.R.W.) Accepted for publication July 12, 2016. Synopsis The skin on the lower legs of 25 female subjects was evaluated fi rst in the winter, and then again in the summer of the same subjects. Barrier function was determined by measuring transepidermal water loss (TEWL), and skin hydration and dryness were evaluated by electrical measurements (Corneometer® CM825) and visual grading. Stratum corneum (SC) was sampled using 10 sequential D-Squame sampling discs and analyzed for 2-pyrrolidone-5-carboxylic acid (PCA), keratin-1,10,11, interleukin 1α (IL-1α), interleukin 1 receptor antagonist (IL-1ra), selected ceramides, cholesterol, cholesterol sulfate, and selected free fatty acids. TEWL as well as the visual dryness grades were signifi cantly lower in the summer while hydration was higher. PCA was signifi cantly higher in the summer as were the keratins. The ratio IL-1ra:IL-1α, an indicator of skin infl ammation, was signifi cantly lower in the summer. The amount of protein removed by the tape strips was also signifi cantly lower in summer indicating better SC cohesion. Among the SC lipids measured, total ceramides, individual ceramides, total fatty acids, and cholesterol were higher in summer compared to winter. Stearic acid and cholesterol sulfate were not signifi cantly different between winter and summer. INTRODUCTION It is well known that dry skin develops more readily in the winter than in the summer. In addition, skin is more responsive to irritants, such as surfactants in cleansing products, during winter as shown in studies involving exaggerated use of washing products (1–3) and on workers who repeatedly use cleansers in their occupations (4–6). Address all correspondence to Randy Wickett at wickterr@ucmail.uc.edu.

JOURNAL OF COSMETIC SCIENCE 186 Previous studies have investigated seasonal differences in biophysical properties of the skin in different populations. Hydration measured by electrical methods has been found to be consistently higher in summer (7–13) but transepidermal water loss (TEWL) differences have not been as consistent. Black et al. (8) reported higher TEWL in summer on the forearm, calf and crows-foot areas whereas Kikuchi et al. (10) reported lower TEWL in summer on the forearms and cheeks of both pre- and postmenopausal Japanese women. Seasonal differences were more marked on the face. Wan et al. reported higher TEWL on the foreheads of Chinese women in autumn and winter compared to spring and summer (7). Muizzuddin et al. reported lower TEWL on the cheek in summer versus winter in subjects living in arid (Arizona) and humid (New York) climates (11). Egawa and Tagami used in vivo confocal Raman spectroscopy to investigate seasonal differences in stratum corneum (SC) components with Japanese subjects (9). Natural moisturizing factor (NMF) components, defi ned as free amino acids and 2-pyrrolidone-5- carboxylic acid (PCA), were not higher in summer compared to other seasons. Urea and lactate were found to be higher in summer, and trans-urocanic acid (t-UA) was found to be lower in summer. Using a tape stripping method on the forearms of Japanese males, Nakagawa et al. also found higher values of urea and lactate in the SC in the summer than in the winter (14). Seasonal changes in SC structural lipids that may contribute to the difference in summer and winter skin condition have been reported in the literature. Increased levels of cerami- des and cholesterol have been reported in summer (9,15,16). Ishikawa et al. reported changes in the ceramide profi les in summer compared to winter, and further that capaci- tance was directly proportional and TEWL inversely proportional to total ceramide level (17). Capacitance was higher in summer on all body sites, but TEWL differences varied with body site. Recently, cytokines such as interleukin 1-α (IL-1α) and interleukin 1 receptor antagonist (IL-1ra) and structural proteins (involucrin and keratin-1,10,11) have been studied as biomarkers of skin health (18–22). The ratio of IL-1ra:IL-1α has been found to increase in skin treated with sodium lauryl sulfate (18,19), and the structural proteins keratin-1,10,11 were reported to be lower in the irritated skin of health-care workers (22). Involucrin was found to be lower and keratin-1,10,11 to be higher in adults’ skin compared with infants’ skin (21). Effective treatment decreased the IL-1ra:IL-α ratio and increased keratin-1,10,11 on the scalp of dandruff sufferers (20). To our knowledge, seasonal differences in these biomarkers have not yet been reported in the literature. The goal of the present study was to evaluate the effect of season on skin health by skin grading, biophysical measurement, and noninvasive sampling for NMF components, bio- markers, and SC lipids. Female subjects were given a mild synthetic detergent bar to use for a one-week prewash during the winter. Subjects who developed at least moderately dry skin on the lower legs were selected for evaluation. The same subjects returned for evaluation during the following summer. After the same prewash procedure, the subjects underwent the same evaluations as in the winter study. Biophysical properties measured were TEWL and hydration (Corneometer). Visual grading was performed to evaluate skin dryness and redness. SC was sampled using 10 sequential D-Squame sampling discs (CUDERM, Dallas, TX) to analyze for SC cohesiveness, NMF components, biomarkers (IL-1ra:IL-α, involucrin, keratin-1,10,11), and SC lipids. The study protocol allowed for direct paired comparison of the same subjects in summer and winter for all properties measured.