Q: I am a 33 years old man who has developed allergy this winter. If I am exposed to sunlight in a car, walking or wherever my body gets a little warmed up I start feeling needle pricks all over my body and soon small red patches appear on my skin. The pricking feeling is so high that I have to move into a shaded or a cooler area and after 10-15 minutes it becomes normal. This has happened for the first time. Please suggest.

A:This sounds like cholinergic urticaria, in which activation of the sweat glands in a hot environment or during exertion is accompanied by a nettle rash, often starting with small itchy weals around active sweat glands. Antihistamines may prevent this if it is difficult to avoid the conditions that precipitate episodes. It is an example of a physical urticaria, and can improve with time, but often takes several years to disappear. It is a harmless but annoying condition of unknown cause.