Determination of threshold UV-A elicitation dose in photopatch testing.
Photopatch testing, although widely used in the diagnosis of photosensitivity disorders, is not standardized. We performed this study to determine the threshold ultraviolet light A (UV-A) dose required to elicit photopatch test responses. 4 patients with previously positive tests were reexposed to the offending allergen, using an incremental dosage regime. Isopropyl dibenzoylmethane (Eusolex 8020), mexenone (benzophenone-10) and oxybenzone (benzophenone-3) produced positive responses at 1.0, 1.0 and 0.7 J/cm2, respectively. Responses to phenothiazines were deemed phototoxic. These results demonstrate that high doses of UV-A (e.g., 10-15 J/cm2) are unnecessary, and that 5 J/cm2 should become the current standard.
Duguid
C
C
Regional Centre of Dermatology, Mater misericordiae Hospital, Dublin, Ireland.
O'Sullivan
D
D
Murphy
G M
GM
D000328:Adult; D000485:Allergens / Q000276:immunology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests / Q000379:methods*; D010787:Photosensitivity Disorders / Q000175:diagnosis* / Q000209:etiology / Q000276:immunology; D011829:Radiation Dosage; D012015:Reference Standards; D012867:Skin / Q000276:immunology; D014466:Ultraviolet Rays / Q000009:adverse effects
D000485:Allergens