A popular commercial sunscreening agent containing the ultraviolet-absorbing chemical glyceryl p-aminobenzoate was found to be a photosensitizer having produced a severe dermatitis in a patient who applied it prior to sun exposure. Three possible mechanisms of action are briefly discussed: photoallergy, phototoxicity, and photoaugmentation. The agent was shown to be an ordinary contact allergen as well as a photosensitizer.
Goldman GC, Epstein E. Contact Photosensitivity Dermatitis From Sun-protective Agent. Arch Dermatol. 1969;100(4):447-449. doi:10.1001/archderm.1969.01610280065011