In vitro absorption of triethanolamine through human skin

The human skin penetration of triethanolamine (TEA) was measured using in vitro diffusion cell techniques. [C-14]TEA was applied to viable skin in an oil-in-water emulsion containing TEA stearate as an emulsifying agent to simulate cosmetic exposure. The percent of the applied dose of TEA absorbed into the receptor fluid was similar with both 1% and 5% TEA formulations. Absorption of TEA was reduced by lowering the pH of the formulation, presumably due to the increased ionization of TEA. Absorption of TEA into the receptor fluid (1% formulation, pH 7.0) was 0.43% of the applied dose in a 24 h study. Substantial amounts of TEA remained in the skin at the end of the study (9.4% of dose), but only minimal amounts diffused into the receptor fluid when the collection time was extended to 72 h in separate studies. The amount of TEA remaining in skin at the end of the 24 h studies should not be included in estimates of systemic absorption.