Effect of indomethacin on UVB- and UVA-induced erythema in polymorphic light eruption

The effect of topical indomethacin on the intensity of UVB- and UVA-induced erythema was measured by reflectance spectrophotometry in 23 patients with polymorphic light eruption. Thirteen patients showed a response to indomethacin that was identical to that seen in normal subjects (i.e., inhibition of UVB-induced erythema; no effect on the intensity of UVA-induced erythema). In the remaining 10 patients indomethacin caused abnormal augmentation of UVB- and UVA-induced erythema. These results show for the first time that the term polymorphic light eruption embraces at least two disease states that have different mechanisms of photosensitivity and that can be distinguished on the basis of clinical features and results of photobiologic investigation.