Development of a preclinical surfactant skin penetration assay to reflect exposure times typical of consumer use.

Mixed surfactant and surfactant-polymer compositions have been reported to decrease surfactant deposition onto and penetration into the skin relative to single surfactant compositions, potentially improving the mildness of the product. Previous workers in this area [see Moore et al., J. Cosmet. Sci.54:29-46 (2003), and subsequent publications] employed a procedure in which excised porcine skin was exposed to a surfactant solution containing radiolabeled sodium dodecyl sulfate (¹⁴C-SDS) for 5 h. We have developed an improved SDS penetration assay using excised human skin that reflects typical consumer exposure times for rinse-off products. Using the new protocol, we were able to see a significant decrease in ¹⁴C-SDS penetration from a sodium lauryl sulfate (SLS)/polyethylene oxide composition applied to excised skin for either 2 or 10 min, as compared to SLS only. Furthermore, differences between the SDS penetration patterns on porcine skin and human skin were seen with a second SLS/polymer system; consequently, we do not recommend porcine skin for routine mildness screening by ¹⁴C-SDS penetration.