A man came to the casualty with some skin lesions after exposure to the sun. He is allergic to sunlight. Solar uicaria is characterized by:

Uncommon sunlight-induced whealing confined to exposed body sites. Eruption occurs within minutes of exposure and resolves in a few hours. Very disabling and sometimes life threatening. Action spectrum is UVB, UVA, and visible light or any combination thereof. Most commonly UVA. Is an immediate type I hypersensitivity response to cutaneous and/or circulating photo allergens. Therapy: multiple phototherapy sessions in low but increasing doses on the same day ("rush hardening"); oral immunosuppressive agents or plasmapheresis. Prevention: sun avoidance, sunscreens with high protection factors against action spectrum. Ref: Suurmond D. (2009). Section 10. Photosensitivity, Photo-Induced Disorders, and Disorders by Ionizing Radiation. In D. Suurmond (Ed),Fitzpatrick's Color Atlas & Synopsis of Clinical Dermatology,6e.