Experimental induction of rough dermatitic skin in humans

The response after application of various concentrations of sodium lauryl sulfate (SLS) on human skin is reported. The induced changes associated variable degrees of roughness and erythema characterizing rough dermatitic skin (RDS). These clinical changes were almost invariably (less than 5% experimental error) associated with increased values of transepidermal water loss (TEWL) and increased cutaneous blood flow values (CBFV). A significant positive correlation was found between TEWL and CBFV at all concentrations of SLS. However, values of TEWL higher than those found in 84% of the controls (mean + SD: 8.127 + 2.89 gr/m2/h) were usually significantly correlated with clearcut clinical changes (total clinical score greater than 2 or erythema greater than 1) at all concentrations of SLS, while CBFV (mean + SD of controls: 2.717 + 2.165) which had a wider dispersion, were significantly associated only with erythema after 10% and 1% SLS. This reflects the distinction that is being made between a primary chemical insult, which we identify clinically as roughness and functionally as increased TEWL associated with alterations of barrier function of the skin, and a secondary, delayed inflammatory response, which is clinically recognized as erythema and functionally objectivated by increased CBFV. These results provide a rational basis supporting the use of this experimental model of RDS for testing of preventive and therapeutic efficacy as well as refining the evaluation of tolerance of cosmetics especially designed for use on sensitive skin.