Cumulative irritation in older and younger skin: a comparison.

Changes in stratum corneum properties due to sodium lauryl sulfate cumulative irritation were determined as a function of age. We irritated the backs of 7 younger (27.7 +/- 4.6 years, mean +/- standard deviation) and 10 older (69.8 +/- 5.5 years) volunteers on 5 consecutive days with open application of a 7.5% aqueous sodium lauryl sulfate solution. Water- and untreated skin served as controls. Transepidermal water loss, stratum corneum capacitance, Desquamation Index, and skin roughness parameters were evaluated on 5 days of the 1st week, and on 3 days of the 2nd week. All parameters revealed a delayed and decreased reaction of older compared to younger skin and recovery appeared to be prolonged. We conclude that under these test conditions irritancy to repetitive sodium lauryl sulfate exposure of older versus younger skin resembled that previously observed after single occlusive exposure. In neither age group was the recovery effect reduced by repeated irritation, demonstrating sufficient skin barrier and recovery function.