Structural and functional differences in barrier properties of African American, Caucasian and East Asian skin

Background: Differences in structural and functional skin characteristics have been linked with ethnical background. But racial differences in skin have not been thoroughly investigated by objective methods and the data are often contradictory. Objectives: This study was undertaken to compare skin barrier-related parameters of the stratum corneum on African American, Caucasian and East Asian skin by objective measurements. Methods: Baseline values of trans epidermal water loss were collected on the face. Consecutive stratum corneum D-squame (R) tape strippings were collected on the panelist's ventral forearm and face to evaluate skin barrier strength and cohesion. Stratum corneum ceramides, maturation, measured as the transglutaminase-mediated cross-linking of stratum corneum proteins, and stratum corneum trypsin like enzyme activity were measured on the D-squame (R) tape strippings. Results: East Asian and to some extent Caucasian skin was characterized by low maturation and relatively weak skin barrier. African American skin was characterized by low ceramide levels and high protein cohesion in the uppermost layers of the stratum corneum. These data can be interpreted in terms of the high prevalence of xerosis in black skin and increased skin sensitivity in East Asian skin. Conclusion: These results demonstrate that skin properties at the level of the stratum corneum vary considerably among these ethnic groups. This contributes to an improved understanding of physiological differences between these study populations. (C) 2010 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.