What is it?
A sun allergy is an immune system reaction to sunlight, most often, an itchy red rash. The most common locations include the “V” of the neck, the back of the hands, the outside surface of the arms and the lower legs. In rare cases, the skin reaction may be more severe, producing hives or small blisters that may even spread to skin in clothed areas.
Causes
Sun allergies are triggered by changes that occur in sun-exposed skin. It is not clear why the body develops this reaction. However, the immune system recognizes some components of the sun-altered skin as “foreign,” and the body activates its immune defenses against them. This produces an allergic reaction that takes the form of a rash, tiny blisters or, rarely, some other type of skin eruption.
Symptoms
Symptoms vary, depending on the specific type of sun allergy:
PMLE – PMLE typically produces an itchy or burning rash within the first two hours after sun exposure.
Actinic prurigo (hereditary PMLE) – Symptoms are similar to those of PMLE, but they usually are concentrated on the face, especially around the lips.
Photoallergic eruption – This usually causes either an itchy red rash or tiny blisters. In some cases, the skin eruption also spreads to skin that was covered by clothing.
Solar urticaria – Hives usually appear on uncovered skin within minutes of exposure to sunlight.
Treatment
PMLE – For mild symptoms, either apply cool compresses (such as a cool, damp washcloth) to the areas of itchy rash, or mist your skin with sprays of cool water.
Actinic prurigo (hereditary PMLE) – Treatment options include prescription-strength corticosteroids, thalidomide (Thalomid), PUVA, antimalarial drugs and beta-carotene.
Solar urticaria – For mild hives, you can try a nonprescription oral antihistamine to relieve itching, or an anti-itch skin cream containing cortisone.
