Solar urticaria is a rare, IgE-mediated, photodermatosis characterized by pruritus, stinging, erythema, and wheal formation after a brief period of exposure to natural sunlight or an artificial light source emitting the appropriate wavelength. (See Presentation.)
Initially described by Merklen in 1904, solar urticaria is localized to exposed areas of the skin, although it can occur through thin clothing. Solar urticaria disappears within several minutes to a few hours, without pigmentary change if further sun exposure is avoided. The condition can be quite disabling and difficult to manage. It often has a sudden, dramatic onset, and little information is available regarding its duration and eventual outcome. (See Prognosis, Presentation, DDx, Treatment, and Medication.)
See the images below.
Solar urticaria. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/reactions/solar-urticaria.jpg).
Solar urticaria. Courtesy of DermNet New Zealand (http://www.dermnetnz.org/assets/Uploads/reactions/solar-urticaria1.jpg).