To investigate differences in response to irritation according to age and site seven young-adult and eight elderly females were exposed to 0.25% sodium lauryl sulphate (SLS) under patch-test occlusion for 24 h. Ten anatomical regions were tested: forehead, upper arm, volar and dorsal forearm, postauricular, palm, abdomen, upper back, thigh, and ankle. The skin responses were evaluated 24 h post-patch removal by visual scoring and by transepidermal water loss measurements (TEWL). Non-treated symmetrical anatomical regions served as controls. SLS induced a mild erythematous reaction on most anatomical regions except the palm and TEWL was significantly increased as compared with controls. The elderly group demonstrated significantly less susceptibility to SLS-induced irritation for most regions of the body as indicated by visual scores and TEWL measurements. In addition, evaluation of the stratum corneum water content following SLS irritation demonstrated lower responses in the old age group for most regions. The thigh had the highest reactivity and the palm the lowest, in both age groups. These data suggest that young adult skin is more sensitive to SLS than old skin and that SLS irritation varies considerably with respect to region. Moreover, objective TEWL measurements seem to be a better indicator of irritant susceptibility, especially in the elderly, than clinical evaluation by visual scoring.