Effect of surfactant mixtures on skin structure and barrier properties.

We investigated the effect of two commonly studied surfactants, sodium dodecyl sulfate (SDS) and dodecyl trimethylammonium bromide (C(12)TAB), on skin barrier properties. Using skin conductivity, FT-IR of stratum corneum samples, and penetration of radiolabelled SDS, we determined that addition of C(12)TAB lowers the ability of SDS to perturb skin's barrier properties. Ultrafiltration experiments revealed that addition of C(12)TAB serves to decrease the concentration of monomers and sub-micellar aggregates. None of the measured skin properties including enhancement of skin conductivity, perturbation of lipid structure and skin concentration of SDS correlated with the total SDS concentration in the donor compartment (i.e., the total SDS concentration). However, all these parameters correlated well against the concentration of monomers and sub-micellar aggregates. These findings provide the evidence of the importance of monomer and sub-micellar components in altering skin barrier properties.