Indoor and outdoor tests were performed on human volunteers to determine the protection offered by six commercially available products containing single sunscreen ingredients and combinations of ingredients. Indoor solar simulator studies were performed to determine the inherent efficacy of each product, including use of a whirlpool treatment to evaluate the resistance of each product to wash off. The outdoor study included a tenminute swimming period followed by sunlight exposure. In all tests, the combination of 7% octyl-dimethyl p-aminobenzoic acid ester and 3% oxybenzone was substantially more effective in protecting against sunburn than any other formula tested, including 5% p-aminobenzoic acid (PABA).
(Arch Dermatol 115:46-49, 1979)
Sayre RM, Marlowe E, Agin PP, LeVee GJ, Rosenberg EW. Performance of Six Sunscreen Formulations on Human SkinA Comparison. Arch Dermatol. 1979;115(1):46-49. doi:10.1001/archderm.1979.04010010018006