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J. Soc. Cosmet. Chem., 29, 265-282 (May 1978) Autoradiographic study on percutaneous absorption of several oils useful for cosmetics M. SUZUKI, K. ASABA, H. KOMATSU and M. MOCHIZUKA Pola Laboratories, 27-1, Takashimadai, Kanagawa-Ku, Yokohama, Japan. Received September 9, 1977. Synopsis PERCUTANEOUS ABSORPTION of five 14C-labelled OILS, n-octadecane, decanoxy decane, 2-hexyldecanoxy octane, isopropyl myristate and glyceryl tri-(oleate), generally used in COSMETICS were studied from the point of view of their safety. In whole body AUTORADIOGRAPHY with hairless mice, there was no visible penetration into the skin and organs, whereas microautoradiography with guinea pigs showed local penetration. Isopropyl myristate penetrated to the greatest extent, whereas 2-hexyldecanoxy octane was hardly absorbed. Percutaneous absorption of these two oils, therefore, was examined in Angora rabbits by microautora- diography simultaneously with skin irritation potential by histological method from the following aspects: 1. patterns of penetration and irritation according to application time and 2. fate within the skin and pattern of irritation after application. In addition, intradermal metabolic fate was also studied in vito. INTRODUCTION Skin irritations or eruptions caused by cosmetics are very serious problems from a social viewpoint. Skin penetration of irritants in cosmetics used topically is a prerequi- site of their causing responses in the living cells of the epidermis and underlying dermis. Thus, cosmetic chemists have long been interested in percutaneous absorption as a very important phenomenon. From the standpoint mentioned above, the authors have been studying percutaneous absorption of cosmetic constituents not only to examine their permeability, but also to evaluate its relationship to the occurrence of irritation and toxicity. The findings re- garding these relations are expected to improve the quality of cosmetics in terms of their safety. Though percutaneous absorption has been measured on some available materials used in small amounts in cosmetics, e.g., germicides (1-4), hormones (5-7), vitamins (8,9) and surfactants (10-12), little data have been reported on the base materials of cos- metics. In this paper, percutaneous absorption of several oils used as bases in cosmetics were studied in hairless mice, guinea pigs and Angora rabbits. 265