PENETRATION OF ANIONIC SURFACTANTS INTO SKIN .3. PENETRATION FROM BUFFERED SODIUM LAURATE SOLUTIONS

[摘要] Penetration occurs from a buffered solution of sodium laurate, if its pH is below 8.5 or above 10.5, but little or no penetration occurs from solutions buffered in the 8.5 to 10.5 pH range. As the pH of an aqueous sodium laurate solution decreases, the ether/water partition coefficient increases, i.e., lipid-solubility increases. Penetration from sodium laurate solution in the pH range of 7.0 to 8.5 is thought to occur because of this increased lipid-solubility. Penetration above 10.5 can be shown to be due to alteration of the major barrier, since a sodium laurate solution which will not penetrate normal skin, does penetrate skin which has been pretreated with a buffer solution of pH 12.0. Patch-test datafor sodium laurate in buffered solutions show that erythema develops at pH 7.5 but not at pH 9.5. For cutaneous irritations caused by soap, it is now necessary to re-evaluate the role of the fatty acids and alkali.