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 Scandin avian standard photopatch series in 29 patients with photocontact and/ or contact allergy to 1 or several of the allergens in that series. Ph otocontact test reactions were more sensitive to allergen dilution tha n plain contact test reactions. Even dilution from the standard 5% to 2.5% or 1.25% significantly reduced para-aminobenzoic acid photocontac t test reactions. Reducing the UVA dose from the standard 5 J/cm(2) to 2.5 or 1 J/cm(2) in 2 out of 5 cases turned a significant (++) reacti on into a doubtful one (+). Increasing the standard WA dose of 5 J/cm( 2) to 20 - 40 J/cm(2) turned a single + photocontact reaction to trich lorcarbanilide and a single 1+ plain contact reaction to chlorhexidine into ++ reactions. In the majority of cases, however, neither photoco ntact nor plain contact test reactions were augmented by UVA doses up to 80 J/cm(2). We conclude that a UVA dose of 5 J/cm(2) is sufficient for eliciting photocontact allergic test reactions, and that a reducti on of either the UVA dose level or the standard allergen concentration s of the Scandinavian photopatch test guidelines may cause loss of sig nificant photocontact test reactions in a proportion of the cases. (C) Munksgaard, 1996.