PERMEATION OF KERATINOUS SUBSTRATES 351 1.6 1.4 1.2 1.0 0.6 0.4 0.2 i 0 8 16 24 HOURS Figure 11. Effect of pretreatment by Polymer JR on permeability of 10% sodium lauryl sulfate. Solid lines: untreated. Dashed lines: pretreated for 1 hr with 1% Polymer JR that Polymer JR is itself highly substantive to stratum corneum (17). Its action may therefore be analogous to the glue-like property of cationic starches which are used to hold cellulose fibrils together in the paper-making process (21). CONCLUSION Diffusion studies have shown that penetration of (radiotagged) sodium lauryl sulfate, SLS, through neonatal rat stratum corneum is relatively rapid and increases with concentration even above the critical micelie concentration. Penetration by a cationic surfactant and a nonionic surfactant was also found but required a period of several days rather than hours as was observed for SLS. It is postulated that the high sorption and diffusion obtained with SLS are due in part to structural changes in the membrane brought about by this surfactant. These changes are mitigated by the preap- plication of a cationic polymer which was observed to reduce markedly the diffusion of SDS through the membrane.

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