Treatment of solar urticaria can be frustrating. A combination of different modalities is often necessary, but the success of these methods is highly variable. Taking measures to avoid or minimize sun exposure is the most important step for patients with solar urticaria. Unfortunately, this often requires major adjustments in lifestyle, which might be impractical for some patients. Long-acting, nonsedating H1-receptor blockers are the first line of treatment for solar urticaria. This is because the disease involves immunoglobulin E (IgE)-mediated mast cell degranulation with consequent histamine release. Phototherapy with UV-A, broadband UV-B, or narrowband UV-B or photochemotherapy with oral methoxsalen (8-methoxypsoralen [8-MOP], a form of psoralen) plus UV-A is also effective for treating solar urticaria.
The following types of solar urticaria have been proposed:
Type I — This type is characterized by an IgE-mediated hypersensitivity to specific photoallergens generated only in solar urticaria patients
Type II — This type is characterized by an IgE-mediated hypersensitivity to nonspecific photoallergens found in solar urticaria patients and in healthy individuals
Patients may report pruritus, erythema, and wheal formation of varying degrees after a short period (< 30 min) of sun exposure. As with most other photodermatoses, skin lesions in solar urticaria may occur on any exposed area, even if skin was covered with thin clothing. The face and the dorsal aspect of the hands, which are chronically exposed to the sun, are less severely affected than other parts of the body, perhaps owing to acclimatization and "hardening."
Phototesting confirms the diagnosis, identifies the action spectrum, and establishes baseline data (eg, minimum urticarial dose) for possible therapeutic interventions and monitoring in the future. Solar urticaria has a wide action spectrum. Perform phototesting using broadband UV-B (290-320 nm), UV-A (320-400 nm), and visible light sources (400-800 nm). Most patients with solar urticaria have provocative wavelengths in the ultraviolet A and visible ranges, especially green or blue.
Phototherapy with UV-A, broadband UV-B, or narrowband UV-B or photochemotherapy with oral 8-MOP plus UV-A is also effective for treating solar urticaria.
For more on solar urticaria, read here.
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Cite this: William James. Fast Five Quiz: Test Yourself on Key Aspects of Summer Skin Conditions - Medscape - Jul 09, 2018.