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PERCUTANEOUS ABSORPTION OF VITAMINS By SAUL H. RUBIN* Presented September 23-24, 1959, Seminar, New York City As ADEQUATE vitamin supply is essential for the preservation of healthy skin, for this is one of the first and major sites where vitamin de- ficiencies become manifest. The dependence of skin health on vitamins has led to investigations of topical application as a means of insuring an ade- quate supply of vitamins to the skin. The early literature on the absorp- tion of vitamins through the skin has been reviewed by Eller and Wolff (1). Subsequent reviews by De Ritter et al. (2) and Siemers and Sleezer (3) describe applications of topical vitamins in the cosmetic industry. The role of the vehicle in absorption has been discussed in detail by Harry (4), Sagarin (5), Hadgraft and Somers (6) and Gemmell and Morrison (7). Gemmell and Morrison (8) and Blank (9) have evaluated a variety of methods which have been devised to estimate the rate of release, amount of penetration and absorption of topically applied medicinal substances from the vehicle. Studies on the penetration of the skin by vitamins have been conducted in animals or humans by similar procedures including: (1) histological examination (2) analysis of skin (3) tracer techniques (4) clinical examination (5) measurement of blood or urine levels (6) analysis of body tissues other than skin (7) observation of a characteristic reaction Histological and clinical examination or chemical analysis of the skin provide evidence of effects at the site of application. Analysis of other tissues or body fluids and occurrence of physiological reactions provide indications not only of local penetration but also of systemic effectiveness. Measurements of vitamin content of body tissues or fluids have been carried out by physicochemical or microbiological methods and more recently by techniques involving radioactive tracing. The use of radioactive vitamins * Hoffmann-La Roche, Inc., Nutley, N.J. 160