Because it is not yet precisely known how and why solar urticaria arises, there is no known therapy at the moment proven to be effective against the causes of the disease. For that reason the attempt is usually made to either prevent the urticarial outbreak through protection against the light or to ameliorate the symptoms. One relatively simple way to protect against exposure to the sun is to use sunscreens with a high light protection factor and that filter out a broad spectrum of light, as well as appropriate clothing and hats–and staying in the shade. While these measures are generally helpful for patients who react to ultraviolet light, they are of little use for urticaria triggered by visible light. Another option for symptomatic treatment is the ingestion of modern non sedating antihistamines that block the effects of histamine, producing roughly a ten-fold increase in light tolerance. This is not enough to aid highly light-sensitive patients who break out in hives after only several seconds in the sun, however. Interestingly, antihistamines inhibit itchiness and wheal formation, but not flaring.
One alternative therapy that has often brought good results is phototherapy (photodesensitisation). It is effective and produces only low side effects, but does require time and effort. Phototherapy involves exposing a portion of the body - and later the entire body - to light of the specific wavelength that triggers urticaria symptoms in the patient. A reliable procedure is available for this kind of treatment, known as UV hardening. UV hardening can produce good sun tolerance within a few days. Similar results can also be striven for through PUVA treatment, a combination of the ingestion o topical application of Psoralen and UVA exposure (photochemical therapy). Psoralen is a substance that increases the light sensitivity of the skin and hence increases the effect of the UVA radiation.
Once primary therapy has been completed for any of these photo therapies, however, follow-up exposure treatments (or repeated, controlled exposure to the sun) should be scheduled to maintain the effectiveness of the acclimation. Severe cases of solar urticaria in which even photodesensitisation treatment fails to produce results, may require treatment with immunosuppressive drugs (drugs that suppress the body's immune reaction) or regular plasmapheresis (haemodialysis). Because these treatment options are accompanied by more serious side effects, these forms of treatment are used only on a case-by-case basis.