RADIAL SPREAD OF SODIUM LAURYL SULFATE AFTER TOPICAL APPLICATION

Purpose. Since topical application of sodium lauryl sulfate (SLS) has been reported to elevate transepidermal water loss and decrease skin c apacitance in areas immediately adjacent to the applied site, studies were carried out to quantify the extent of radial spread of SLS below a topically exposed site in a hairless rat model. Methods. Fixed sites were demarcated and the levels of SLS measured around the applied sit e in the epidermis, dermis and the subcutaneous tissues. Underlying de ep tissue penetration and radial spread of SLS in the presence and abs ence of a vasoconstrictor, phenylephrine, was also quantified. Results . In a typical 24 hour study, the radial spread of SLS was observed to a distance of similar to 0.75 cm from the applied site. The use of ph enylephrine (1:20000), did not significantly enhance either the local underlying tissue (apart from underlying epidermis) concentration or r adial spread of SLS relative to no vasoconstrictor treatment. Conclusi ons. Given that SLS impairs barrier function of the skin, its radial s pread could be explained by a passive diffusion process. Vasoconstrict or did not remarkably alter SLS penetration and radial spread possibly due to the competing effects of vasodilation (caused by SLS) and vaso constriction (caused by phenylephrine).