Ethnic differences in objective and subjective skin irritation response: an international study

Background Due to global marketing in the cosmetics industry, it is important to assess ethnic population susceptibility when evaluating the safety of cosmetic products or chemicals. Objectives To investigate ethnic variations in skin irritation response to positive irritants. Methods Clinical testing was performed in four countries on two ethnic groups – Asian and Caucasian. We performed patch tests on the subjects’ back with 0.5% aqueous sodium lauryl sulfate (SLS) and 0.15% retinol prepared in 1,3-butylene glycol. Stinging tests were performed using 5% aqueous lactic acid and 0.001% (w/v) capsaicin prepared in 10% ethanol solution separately. Results The incidence of self-perceived skin sensitivity was similar in the two ethnic groups. However, the incidence of adverse skin reaction to cosmetics appeared significantly higher in Asian (33.0%) than in Caucasian subjects (11.3%). For standard positive irritants such as 0.5% aqueous SLS solution, Asian subjects showed significantly higher scores than Caucasian subjects. The incidence of positive reaction to the 0.15% retinol patch test tended to be higher in Asian than in Caucasian subjects. Our data also showed that neurosensitivity to 5% lactic acid and 0.001% capsaicin was higher in Asian than in Caucasian subjects. Conclusion Although self-reported skin sensitivity does not appear to differ according to ethnicity, there are ethnic differences in objective and subjective skin irritation responses to several standard positive materials.