Determination of threshold UV-A elicitation dose in photopatch testing.

Photopatch testing, although widely used in the diagnosis o1' 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 teats were rexposed to the offending allergen, using in incremental dosage regime. Isopropyl dibenzoylmethane (Eusolex 8020). mexenone (benzophenone-l0) and oxybenzone (benzophenone-3) produced positive responses at 1.0. 1.0 and 0.7 J/cm, respectively. Responses to phenothiazines were deemed photoxic. These results demonstrate that high doses of UV-A e.g. l0 15 J/cm) are unnecessary. and that 5 J/cm[sup2] should become the current standard. [ABSTRACT FROM AUTHOR]