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j. Cosmet. Sci., 50, 147-157 (May/June 1999) Skin penetration properties of cosmetic formulations using a perfused bovine udder model TH. F(SRSTER, W. PITTERMANN, M. SCHMITT, and M. KIETZMANN, Henkel KGaA, D-40191 Diisseldorf and Institute of Pharmacology, Toxicology and Pharmac•y, School of Veterinary Medicine, D-30559 Hannover, Germany Accepted for publication April 30, 1999. Presented at the XXth Congress of the International Federation of the Societies of Cosmetic Chemists, Cannes, France, September 14-18, 1998. Presented in part at Penetration, Leiden, The Netherlands, September 22-26, 1998. Synopsis Bioactives are a major focus of the recent developments in cosmetics. Most of these ingredients will work only if they penetrate the stratum corneum and reach the living epidermis. The extent and rate of pen- etration of bioactive ingredients from cosmetic products is of paramount interest. A systematic in vitro study of penetration into stratum corneum and viable skin was performed using the isolated perfused bovine udder skin (BUS) model. As bioactive ingredients, oil-soluble vitamin E, vitamin E acetate, and water-soluble D-panthenol were incorporated into different cream formulations and a shower gel. Under leave-on conditions (exposure periods of one hour and five hours), the changes in phase behavior and viscosity have a strong impact on the penetration pattern. Generally, the water-soluble D-panthenol penetrates faster and in a higher amount into the stratum corneum than the oil-soluble vitamin E. Regarding the choice of the galenic vehicles, the penetration of both the oil-soluble and water-soluble vitamin is faster and much higher from w/o-cream than from lameIlar o/w-cream due to changes in phase behavior. In contrast to the lamellar o/w-emulsion, for the w/o-emulsion there is no difference in the penetration of vitamin E between one hour and five hours (e.g., a steady state is already reached after an exposure period of 1 h). The top ten skin layers (200 pm depth) again reflect the influence of the emulsion formulation on the vitamin E absorption. From the w/o-cream the penetration is faster and more efficient than from the lameliar o/w-cream. Under rinse-off conditions (3*2 minutes), the water-soluble D-panthenol penetrates in a higher amount than the oil-soluble vitamin. However, the penetration effect is detectable even after the extremely short period of exposure. Due to the fact that the shower gel will not change the phase behavior, different routes of penetration may be considered for water- and oil-soluble vitamins. INTRODUCTION Today's cosmetic emulsions are not simply mixtures of oil, water, and emulsifier, but they also contain a lot of active ingredients whose function is to ameliorate the condition 147