Variation in response of human skin to irritant challenge.

A major obstacle to the establishment of a protocol for in vivo irritant skin testing in humans is the apparent variability of responses between individuals. This study of the threshold response of normal human skin to a standard irritant (sodium lauryl sulfate 0.3-10%), in a group of 22 subjects, revealed a marked interindividual variation in their threshold reaction. The results demonstrate that this phenomenon does exist and that it will have to be allowed for in future human irritant test systems or assays.