Solar urticaria. Report of an unusual case.

Solar urticaria is a relatively rare dermatosis. In reported cases, skin lesions appeared soon after sunlight irradiation, usually within a few minutes, and consisted of a wheal localized to the exposed area with a surrounding flare. The case presented herein is quite different from the others in its clinical manifestation. The time required for the formation of the wheal was far longer and there was neither surrounding flare nor pseudopodia. Also, the degree of local edema was directly proportional to the length of exposure time, up to three hours. A diagnosis of solar urticaria had not previously been made in this patient because he did not show wheal formation except after unusually long exposure.