Photopatch test reactivity: effect of photoallergen concentration and UVA dosaging.
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.
Hasan
T
T
Department of Dermatology, University of Tampere, Finland.
Jansen
C T
CT
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
D000485:Allergens; D000891:Anti-Infective Agents, Local; D002224:Carbanilides; D013473:Sunscreening Agents; C009540:triclocarban; D002710:Chlorhexidine; D010129:4-Aminobenzoic Acid