title: Photopatch test reactivity: effect of photoallergen concentration and UVA dosaging.
abstract: We have studied the influence of variations in allergen concentration and UVA dosaging on the results of photopatch testing with the Scandinavian standard photopatch series in 29 patients with photocontact and/or contact allergy to 1 or several of the allergens in that series. Photocontact test reactions were more sensitive to allergen dilution than plain contact test reactions. Even dilution from the standard 5% to 2.5% significantly reduced para-aminobenzoic acid photocontact test reactions. Reducing the UVA dose from the standard 5 J/cm2 to 2.5 or 1 J/cm2 in 2 out of 5 cases turned a significant (++) reaction into a doubtful one (+). Increasing the standard UVA dose of 5 J/ cm2 to 20-40 J/cm2 turned a single + photocontact reaction to trichlorcarbanilide and a single 1 + plain contact reaction to chlorhexidine into ++ reactions. In the majority of cases, however, neither photocontact nor plain contact test reactions were augemented by UVA doses up to 80 J/cm2. We conclude that a UVA dose of 5 J/cm2 is sufficient for eliciting photocontact allergic test reactions, and that a reduction of either the UVA dose level or the standard allergen concentrations of the Scandinavian photopatch test guidelines may cause loss of significant photocontact test reactions in a proportion of the cases.
authors.affiliation: Department of Dermatology, University of Tampere, Finland.
authors.forename: T
authors.initials: T
authors.lastname: Hasan
authors.forename: C T
authors.initials: CT
authors.lastname: Jansen
mesh_terms: D010129:4-Aminobenzoic Acid / Q000008:administration & dosage / Q000009:adverse effects; D000328:Adult; D000368:Aged; D000485:Allergens / Q000008:administration & dosage* / Q000009:adverse effects; D000891:Anti-Infective Agents, Local / Q000008:administration & dosage / Q000009:adverse effects; D002224:Carbanilides / Q000008:administration & dosage / Q000009:adverse effects; D002710:Chlorhexidine / Q000008:administration & dosage / Q000009:adverse effects; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis / Q000503:physiopathology; D017454:Dermatitis, Photoallergic / Q000175:diagnosis* / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005260:Female; D017408:Guidelines as Topic; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests / Q000379:methods* / Q000592:standards; D011829:Radiation Dosage; D012537:Scandinavian and Nordic Countries; D013473:Sunscreening Agents / Q000008:administration & dosage / Q000009:adverse effects; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: D000485:Allergens; D000891:Anti-Infective Agents, Local; D002224:Carbanilides; D013473:Sunscreening Agents; C009540:triclocarban; D002710:Chlorhexidine; D010129:4-Aminobenzoic Acid