Determination of lysosomal acid phosphatase in human skin as a marker of irritation following different surfactant treatments

Acid phosphatase activity in tape-strip biopsies of human stratum corneum was determined using p-nitrophenyl phosphate as substrate following skin treatment of healthy volunteers with different surfactants at various concentrations. As a short-term effect, enhanced reduction of acid phosphatase activity with stronger surfactants and higher surfactant concentrations was detected. When the skin of panellists was exposed to surfactants in the standardized elbow washing test, a significant long-term increase of lysosomal horny layer acid phosphatase was observed after four or eight days following the final surfactant reatment. This long-term response was found to correlate very closely with the visual scoring system of erythema. Therefore, this assay may serve as a valuable tool for the prediction of skin irritancy and mildness of dilute surfactant solutions. Furthermore, this method is inexpensive, convenient, and avoids the use of animal model systems.