Therapeutic responses to topical administration of preparations containing 0.1% to 0.3% vitamin A acid and control bases applied to contralateral areas of involvement were compared in 26 patients with psoriasis, 8 with ichthyosis vulgaris, 8 with X-linked ichthyosis, 17 with lamellar ichthyosis, and 10 with epidermolytic hyperkeratosis. Topical administration of vitamin A acid was most effective in psoriasis, lamellar ichthyosis, and epidermolytic hyperkeratosis, disorders associated with epidermal cell hyperplasia; it did not appear to be effective in ichthyosis vulgaris. Irritation with higher concentrations of vitamin A acid, which subsided rapidly when the medication was withheld, was the only adverse effect noted.
Frost P, Weinstein GD. Topical Administration of Vitamin A Acid for Ichthyosiform Dermatoses and Psoriasis. JAMA. 1969;207(10):1863–1868. doi:10.1001/jama.1969.03150230077007