Allergic contact photodermatitis to para-aminobenzoic acid

Allergic photocontact dermatitis developed in a patient to a commercial sunscreen preparation containing para-aminobenzoic acid (PABA) in an alcohol base. Photopatch testing showed photosensitivity to PABA. Sensitization could only be detected when PABA was tested in an alcohol vehicle; a photopatch test to PABA in petrolatum was negative.