Robert J. Feldmann and Howard I. Maibach
Published: The Journal of Investigative Dermatology, January 2, 1970 © 1970 by The William & Wilkins Co.
This article describes an in-vivo study on the percutaneous penetration of several organic chemicals, including nicotinic acid (niacin) and niacinamide, after application to the human forearm and quantitating the penetration of each chemical through the skin by its appearance in urine.
- “…Nicotinic acid showed minimal penetration while 10% of its amide, nicotinamide, was absorbed…” (emphasis added)
- “…Nicotinic acid penetrated in a quantity less than 1% of the applied dose… Nicotinic acid was applied to human kin in vitro by Cronin and Stoughton... They noted no penetration in several specimens and an average of 0.001% of the applied dose in other specimens. Our in vivo data also suggest that it is a minimal penetrant” (emphasis added)