Solar urticaria. Further studies on the role of inhibition spectra.

A 27-year-old woman exhibited an urticaria only to monochromatic light in the range from 400 to 525 nm, but not to polychromatic light longer than 360-nm ultraviolet (UV) and visible light. An urticarial response induced by 475-nm monochromatic light was completely inhibited by preirradiation, simultaneous irradiation, and postirradiation with light having wave bands longer than 650 nm. Two other patients with sunlight-induced solar urticaria, who had an erythema-and-wheal reaction during and after exposure to sunlight, had no suppressive wave bands in either the UV or visible-light range. These observations strongly indicate an important role for inhibition wave bands in the development of light-induced immediate erythema and urticaria. In some cases of solar urticaria, preirradiation and postirradiation with longer visible light wavelengths could be useful in preventing the development of urticaria.