Sun allergy

After long winter months, most of us can hardly wait to feel the warmth of the sun again. But for a small minority, the sun is not welcome at all.

Sometimes known as sun poisoning, people with solar urticaria develop a stinging, itchy, red and swollen rash shortly after being exposed to the sun.

Surprisingly, the rash may occur in the parts of the body least exposed to the sun, such as the back. The hands and face may be only slightly affected, perhaps because they are desensitised with constant exposure to sunlight.

If large parts of the body are affected, too much fluid loss to the skin can cause light-headedness, nausea, vomiting and even shock.

Although the exact cause of solar urticaria remains a mystery, it is thought that it may be due to the sun reacting with a chemical allergen in the body, causing the allergic reaction responsible for the symptoms.

Diagnosis of solar urticaria is usually confirmed by tests which involve shining light of different wavelengths on the skin.

People with the condition may be treated with antihistamines to help inhibit symptoms, receive phototherapy to desensitise them to sunlight or, in the most severe cases, given immunosuppressant drugs as a last resort.

This article was published on Thu 19 November 2009