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Saturday, June 24, 2017
Skin Care and Diseases
Skin thickness & races...
Is there a difference in thickness in the layers of the skin (s.corneum, granulosum...) amongst different races - Hispanic, African American, Cacausian... If so, with which layer of the skin? Does it effect the effectivenss of transdermal (not topical) therapies with regards to the resevoir effect taking place below the stratum corneum?
The information regarding skin thickness can be found in Richards GM, Oresajo CO, Halder RM. Structure and function of ethnic skin and hair. Dermatol Clin. 2003. Oct;21(4):595-600. Briefly, the stratum corneum, or the outer most layer of the skin of blacks has been shown to be made up of more layers when compared with that of whites. The overall thickness of this layer in white and black skin is generally similar, however in black skin it seems to be more compact, accounting for the greater number of layers. Comparison of epidermis of different racial groups White Stratum corneum thickness 7.2 mm Stratum corneum layers 17 layers Stratum lucidum 1-2 layers. On exposure to sun becomes swollen distinctly cellular Water barrier High Melanosomes Small; group melanosomes in keratinocytes less dense more numerous in subcutaneous than basal layer Black Stratum corneum thickness 6.5 mm Stratum corneum layers 22 layers Stratum lucidum 1-2 layers Remains compact and unaltered with sun exposure Water barrier Low Melanosomes Larger; individually dispersed melanosomes in keratinocytes more numerous in basal layer Differences have been found among blacks, whites, Asians, and Hispanics in various areas of skin structure and function. Among them is the stratum corneum lipid (ceramide) content, which is highest in Asians, then Hispanics, then whites, and lowest in blacks. Melanosomal packaging and percutaneous absorption rates for specific compounds also vary among the different races. Reports supporting the occurrence of difference in transepidermal water loss, tyrosinase levels, skin elasticity, and water absorption rates between blacks and whites, and reaction to skin irritation have been conflicting. No significant differences in corneocyte size, skin thickness, and skin biomechanics have been reported.
Tatiana M Oberyszyn, PhD
Associate Professor of Pathology
Associate Professor of Molecular Virology, Immunology & Medical Genetics
College of Medicine
The Ohio State University