A reader asks: I have recently had several episodes where my skin has come out in large itchy red blotches, like hives. I’ve realised it happens after I have been playing hockey and become hot and sweaty. The last time this happened I felt a bit faint as well. Could I be allergic to my own sweat?
Dr Rosemary Leonard replies: I suspect that rather than being allergic to your sweat, it’s the exercise that is to blame. Although rare, exercise can trigger allergic reactions, including itchy skin rashes, headaches, feeling faint and in more serious cases, swelling of the mouth and tongue, and breathing difficulties.
The exact reason it happens isn’t known, but it is thought that the increase in body temperature that occurs during exercise triggers cells of the immune system to release chemicals that lead to inflammation in the skin and elsewhere in the body. It can happen at any age, including childhood, but appears to occur more commonly in young women.
Sometimes this allergy may be linked to eating certain foods before exercise, so it is worth keeping a diary to check your intake, including energy snacks and drinks.
Trying to prevent getting too hot and sweaty while exercising can sometimes help, but rather than wearing antiperspirant (other than on your armpits) just make sure you are wearing sports clothing that allows your sweat to evaporate, such as those made from special wicking fibres.
Unfortunately, there is no way of preventing it completely, but taking an antihistamine tablet before exercising may help and it would be worth asking your GP for a referral to an allergy specialist to confirm the diagnosis and give further advice.
If you have a health question for Dr Leonard, email her in confidence at [email protected]. She regrets she cannot enter into personal correspondence or reply to everyone