Table 1 (3-12) quantifies our knowledge of ethnic differences in skin for TEWL. Most studies assessed the TEWL on the forearm, back, and inner thigh.
Berardesca and Maibach (4) supported the findings that TEWL is higher in blacks in their 1988 study. The investigators determined the difference in irritation between young black and white patients by applying the irritant 0.5% sodium lauryl sulfate (SLS) to untreated, pre-occluded skin. They found a statistically significant difference in the TEWL, with blacks having 2.7 times higher TEWL levels than whites (P < 0.04), suggesting that black skin in the pre-occluded state is more susceptible to irritation (Table 1). Hispanics were found to have higher TEWL values compared to whites, but this was not statistically significant (5). At baseline, Sugino et al. found TEWL to be blacks > Caucasians > Hispanics > Asians. After tape stripping, Berardesca and Maibach (4) found that TEWL is 1.2 times higher in black women than in Caucasian women on the midvolar forearm. Data from the studies in Table 1 are conflicting, possibly due to testing on different anatomic sites.
All the evidence supports that blacks have higher TEWL than whites, except for Berardesca et al. (6), who found no significant difference and Warrier et al., who found TEWL blacks < whites. TEWL measurements of Asian skin are inconclusive, as they have been found to be equal to black skin and greater than Caucasian skin (7), and less than all the other ethnic groups (8). Future research should include more races and larger sample sizes.
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