j. Soc. Cosmet. Chem., 47, 229-240 (July/August 1996) A comparison of black and white skin using noninvasive methods A. G. WARRIER, A. M. KLIGMAN, R. A. HARPER, J. BOWMAN, and R. R. WICKETT, College of Pharmacy, University of Cincinnati, 3223 Eden Avenue, Cincinnati, OH 45267-0004 (A. G. W., R.R. W. ), Department of Dermatology, University of Pennsylvania, 422 Curie Boulevard, Philadelphia, PA 19104-6142 (A.M.K.), and Hill Top Research, Inc., P.O. Box 429501, Cincinnati, OH 45242 (R.A.H., J.B.). Accepted for publication July 31, 1996. Synopsis Differences in the characteristics of black and white skin were investigated in thirty black and thirty white female subjects between the ages of 18 and 45, using noninvasive methods. Parameters studied included transepidermal water loss (TEWL), electrical capacitance, skin pH, elasticity, dryness/scaling, and skin surface microflora. TEWL was found to be significantly lower on the cheeks and legs in blacks as compared to whites. Black facial skin exhibited higher elasticity and electrical capacitance values. The desquamation index was found to be higher in white subjects on the cheeks and forehead, whereas dryness scores were significantly higher for blacks on the legs. Whites had slightly higher pH than blacks. Overall density of Propionibacterium acnes was found to be higher in blacks. No significant differences were found in the aerobic skin surface microflora. Results from the present study will help gain a better understanding of the variations in characteristics of black and white skin. INTRODUCTION Recent studies have revealed that the differences between the skin of whites and blacks extend well beyond the degree of melanin pigmentation. Yet, comparative studies of the structural and physiologic characteristics are sparse, limited, and sometimes contradic- tory. Studies have shown that though the black and white stratum corneum (SC) are equal in thickness (1), black SC contains more compact layers of corneocytes and exhibits greater resistance to cellophane tape stripping than Caucasoid SC (2). Increased levels of epi- dermal lipids have also been reported for blacks (3). Though it is generally believed that black skin is a more effective barrier to certain chemicals and irritants (2,4,5), higher TEWL and SC water content due to surfactant barrier damage have been reported (6,7). On the contrary, increased electrical resistance (8,9) and decreased inflammatory re- sponses (2,4,5) have been demonstrated in blacks as compared to whites. Investigations 229

230 jOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS of racial differences in conductance, TEWL, and biomechanical properties in sun- protected and non-sun-exposed areas of the skin have shown that water content, ex- tensibility, recovery, and elastic modulus are higher for blacks in sun-exposed areas as compared to whites (10). With regard to physiologic differences, the literature presents a confusing picture. The present study was undertaken in order to gain a better understanding of the fundamental differences between black and white skin. MATERIALS AND METHODS SUBJECTS Thirty black and thirty white subjects were enrolled. Each group consisted of age- matched women between the ages of 18 and 45. Informed consent was obtained from all subjects. The participants used Dove © soap and refrained from using cosmetics, lotions, and antibacterial soaps 48 hours before the study and throughout the duration of the study. SEASON AND LOCATION The study was conducted in Cincinnati, Ohio, over a six week-period in winter from December through February, when temperatures and relative humidity are low and the frequency of dry skin (winter xerosis) is high. Approximately five age-matched black and white subjects were evaluated each week. SCREENING PHASE We selected subjects who represented opposite poles in skin pigmentation: very dark blacks versus light-skinned whites. The Minolta Chroma Meter (Minolta Camera Co., Ltd., Osaka, Japan) was used to obtain L* values on the upper inner arms, according to the Commission Internationale de l'Eclairage (CIE) system in which L* represents the level of brightness or luminescence (! 1). A low L* value indicates low reflectance of light (higher absorption). We screened about 45 subjects per group to select 30 blacks with the lowest L* values and 30 whites with the highest L* values. STUDIES The subjects were equilibrated for 30 minutes in an environmentally controlled room before measurements. The temperature ranged between 19 and 22øC, and the relative humidity varied between 25 and 36%. An area of 6.25 cm 2 was delineated on the left and right medial cheeks, mid-volar forearms, and lateral mid-lower legs. Transepidermal water loss TEWL (g/m2/h) was measured using the Servo-Med © Evaporimeter EP1 (Servo-Med, Stockholm, Sweden). Two measurements were made at each site and averaged.