Chronic photosensitivity.

Chronic photosensitivity is an incompletely understood syndrome that is difficult to diagnose and treat. Persistent light reaction, actinic reticuloid, and photosensitive eczema most commonly occur in middle-aged and elderly patients and have overlapping features. These conditions may all be persistent light reactions to known and unknown photosensitizers. Actinic prurigo usually occurs in childhood but may be delayed in onset to adult life; it is frequently associated with atopy. The diagnosis of these conditions requires a detailed history, histologic examination of the skin, phototesting, and photopatch testing. A conservative approach to therapy consists of avoidance of the activating wavelengths and use of topical corticosteroids. However, this treatment is often unsuccessful, and PUVA therapy is an effective alternative approach.