Ultraviolet and Visible Action Spectrum in a Case of Solar Urticaria

A patient with solar urticaria had an action spectrum for immediate erythema and whealing which extended from 250 nm to 460 nm. The delayed erythema action spectrum was normal. Pulse-meter studies indicated that dilatation of cutaneous arterioles occurred with the immediate erythema; no kinins could be detected in the dermal perfusate from the area. The patient received psoralen therapy orally, and increasing exposure to natural sunlight increased his tolerance to sunlight. Monochromatic light tests showed that the minimal dose for whealing on exposed skin increased after treatment.