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Synopsis Absorption through human skin of a series of six p-hydroxy-benzoates (parabens) was studied in vitro. A diffusion chamber was used, where the receiving phase was a physiological solution of albumin. Maximum fluxes and permeability constants of the parabens were measured from different vehicles representing hydrophilic and lipophilic phases, and from different types of common commercial cosmetic emulsions, each containing a known quantity of a single member of the series. Significant skin absorption was observed, depending upon the partition coefficient (log P octanol/water) of the permeant, composition and time of storage of the emulsions. Fluxes from all types of emulsions were higher for methyl paraben and decreased with the increasing lipophilic character of the preservative. Comparatively, fluxes from oil/water emulsions were higher than from water/oil emulsions. Moreover, a clear dependence of preservatives'percutaneous absorption on the time of storage was observed, the fluxes becoming constant after about three months after the time of preparation. The relationship between preservative activity and percutaneous absorption is discussed.
Pozzo et al. (Mon,) studied this question.