Solar urticaria. Clinical features and wavelength dependence.

Solar urticaria, an uncommon photosensitivity disorder, may be disabling for affected patients, especially those who react after short exposures to artificial or natural light. The spectrodermograph, a newly developed instrument, permits rapid, accurate determination of the action spectrum of solar urticaria. It consists of a xenon arc lamp with an emission dispersed into used to establish the wavelengths responsible for solar urticaria in 12 patients during the past four years. Knowledge of the wavelengths responsible for producing the urticarial reaction has implications for selecting appropriate therapy. The clinical course of these patients is also reviewed.