Solar urticaria in an infant.

A 2-year-old girl presented with a history of an erythematous rash which occurred immediately after exposure to sunlight and had been a problem since birth. Extensive laboratory investigations to exclude genophotodermatoses, photosensitivity secondary to metabolic disorders and photoaggravated dermatoses were negative. Monochromator irradiation phototesting demonstrated immediate erythematous flares to all ultraviolet B (UVB), UVA and visible wavelengths up to 500 nm. A diagnosis of solar urticaria was made and she responded to loratidine 10 mg daily. We believe this is the first report of solar urticaria, confirmed by phototesting with a monochromator so early in life.