Temperature-dependent effect of skin-cleansing products on human stratum corneum

The effect of temperature on surfactant-induced irritant reaction has not yet been thoroughly studied. This study was undertaken to evaluate the effect of temperature on the ex vivo corneosurfametry test, which is a nonanimal alternative method to evaluate the safety of cleansing products. The colorimetric index of mildness (CIM), which correlates with surfactant mildness, was measured using the corneosurfametry test performed on stratum corneum harvested from normal individuals. Sodium lauryl sulfate (SLS) at 1 and 2% concentrations and water were tested at 4, 20, and 40 degrees C. In addition, 5% solutions of 14 proprietary skin-cleansing products were compared at 20 and 40 degrees C. Surfactant CIM decreased with increasing temperature, and was significantly lower than water-CIM at each test temperature. A significant logarithmic correlation was found between the 20 degrees C-CIM and the 40 degrees C-CIM of all test products. The CIM intraindividual variations increased with the irritation potential of products. It is concluded that the corneosurfametry test is influenced by temperature and is a useful tool for predicting the irritancy of surfactants at a given temperature. The CIM variability for harsh products reflects the range of skin susceptibility to irritants in the population and probably illustrates one facet of sensitive skin.