It occurs when body temperature rises during exercise, as it always does. The increased temperature leads to a release of acetylcholine, a body chemical that transmits messages from nerves to muscles and other body tissues and organs. Acetylcholine, in your wife s case, causes a release of histamine. Histamine, in turn, produces an itchy rash of red dots. The rash goes away within 30 minutes to four hours after a person stops exercising.
Antihistamines taken before exercise can prevent the reaction.
Her doctor can prescribe antihistamines in larger amounts. The doctor can also use the newer antihistamines, such as cetirizine and loratadine, two antihistamines that do not cause drowsiness. Your wife should not exercise on a hot day. If she can find an air-conditioned club, the air conditioning might stop the rise in body temperature. Have her try it before she signs up for a membership.