Further studies with 5% hydroalcoholic solution of aminobenzoic acid showed the following: (1) A total of 60μl/sq cm usually gave complete protection against 30 minimal erythemal doses (MEDs). (2) Daily application greatly enhanced the amount and duration of protection. (3) The amount of residual protection after ten minutes' water immersion was greatest two hours after application, and practically nil immediately. (4) In immersion tests, 5% aminobenzoic acid was superior to four other brand name sunscreens: Sea & Ski, Pabafilm, Block Out, and Solbar. (5) Hydrating the skin for two hours before application greatly enhanced the residual protection after immersion. (6) Aminobenzoic acid provided some protection against phototoxic reactions induced by crude coal tar and oxypsoralen. Oral phototoxic effects from demeclocycline hydrochloride was prevented.
Langner A, Kligman AM. Further Sunscreen Studies of Aminobenzoic Acid. Arch Dermatol. 1972;105(6):851-855. doi:10.1001/archderm.1972.01620090023004