DIFFERENCES IN STRATUM-CORNEUM PH GRADIENT WHEN COMPARING WHITE CAUCASIAN AND BLACK AFRICAN-AMERICAN SKIN

This study assessed pH gradient changes in relation to stratum corneum (SC) depth and possible differences between white caucasian and black African-American skin. Ten white and eight black people entered the s tudy, SC was progressively removed by cellophane tape stripping on the volar forearm and weighed with a microbalance. Transepidermal water l oss (TEWL) and SC pH were measured every three tape strippings. Signif icantly increased TEWL and decreased pH values were found with increas ing SC depth in both races. Significantly increased TEWL in black peop le was found after three and six tape strippings (P<0.05 and 0.03, res pectively); pH was significantly decreased in black people after three tape strippings (P<0.005). No differences were found between the race s after nine, 12 and 15 strippings, i.e. in the deeper SC layers. The data confirm that pH in the superficial SC layers decreases with SC de pth; only total SC removal results in increased pH values, In the supe rficial layers, there are significant differences in both water evapor ation and skin pH, possibly explaining the contradictory literature.