Absorption of Some Organic Compounds Through the Skin in Man

We studied the percutaneous penetration of 21 organic chemicals. The experimental method consisted of the application of the chemical to the human forearm and quantitating its penetration through the skin by its appearance in urine.There was a great diversity in the ability of the chemicals to penetrate human skin. Compounds such as hippuric acid, nicotinic acid, and nitrobenzene support the generally held view of the excellent chemical barrier properties for them.Closely related compounds showed great differences in penetration. Benzoic acid was absorbed at 200 times the amount of its glycine conjugate—hippuric acid. Nicotinic acid barely penetrated; 10% of its amide, nicotinamide, penetrated. This suggests that molecules may be tailored to decrease or increase penetration as needed for the most suitable biological function