Fixed solar urticaria to visible light successfully treated with fexofenadine.

Fixed solar urticaria (FSU) represents an uncommon form of urticaria related mostly to radiation from the ultraviolet (UVB, UVA) and visible spectrum. The exact pathomechanism has so far remained unknown. A 52-year-old woman with a 3-year history of urticated eruptions limited to certain skin areas is presented. Photobiological testing revealed positive reactions limited to the visible light range. The induced lesions appeared only in originally affected skin sites. The particular distribution of whealing supports the concept of specific alteration of mast cells in well defined areas. The clinical findings and the results of phototesting lead to the diagnosis of FSU to visible light. It is recommended to carry out phototesting in patients with FSU in the originally affected skin areas, usually covered and protected by the patient, to avoid false-negative results. Fexofenadine given in the conventional dosage can prevent recurrences and represents a successful treatment measure when dealing with this peculiar form of solar urticaria.