No preferential beneficial response was seen to vitamin A acid in seven psoriatic patients using vitamin A acid cream, 0.05%, as tested in a double-blind manner against placebo cream for 12 weeks or, in 11 patients, tested with concentrations varying from 0.1% to 1.0% in comparison with a corticosteroid cream. Three of eight patients tested in a double-blind manner with 0.25% vitamin A acid cream under plastic occlusion initially showed preferential response to vitamin A acid. This response was less than one month's duration in two patients, and three months' in the third. These patients failed to respond to subsequent topical vitamin A. Brief beneficial responses observed in these three patients suggest that further clinical research is needed with emphasis on alternate dosage schedules or use of vitamin A acid combined with other antipsoriatic agents.
Peck GL, Key DJ, Guss SB. Topical Vitamin A Acid in the Treatment of Psoriasis. Arch Dermatol. 1973;107(2):245-248. doi:10.1001/archderm.1973.01620170057015