The therapeutic effectiveness of four local forms of treatment was compared in acne vulgaris: (a) sulfur-resorcinol; (b) benzoyl peroxide; (c) vitamin A acid; and, (d) an inert vehicle. The method of assessment was counting all the lesions on one side of the face at weekly intervals. The order of increasing therapeutic efficacy was: vehicle, sulfur-resorcinol, benzoyl peroxide, and vitamin A acid.
Vitamin A acid increased the rate of production of loose horny cells in the follicular canal, thus preventing formation of comedones and unseating existing ones.
The treatment frequently produces a worsening of the clinical picture during the initial phase of therapy. It is palliative, not curative; relapses occasionally occur when treatment is stopped.
Kligman AM, Fulton JE, Plewig G. Topical Vitamin A Acid in Acne Vulgaris. Arch Dermatol. 1969;99(4):469-476. doi:10.1001/archderm.1969.01610220097017