What are Heat Hives?

Susan Grindstaff

Heat hives, which are also known as cholinergic urticaria, are hives that occur as a reaction to an increase of body temperature. The hives usually appear as small red bumps, usually about the size of a mosquito bite. The rash may be in patches or all over the body. Sometimes, if the rash lingers, the bumps may join to form large irritated areas of skin. The exact cause of the condition is not completely understood, but some research has led to the conclusion that people who suffer the condition may be having an allergic reaction to their own body sweat.

Small cluster of heat hives.
Small cluster of heat hives.

People who experience these hives may have other symptoms as well. In some cases, the hives may cause itching or stinging. In severe cases, some people also may have breathing difficulties and experience a lowering of blood pressure. For some individuals, the appearance of this type of rash is believed to be a trigger for asthma attacks.

Anti-itch cream can be applied to alleviate the symptoms of hives.
Anti-itch cream can be applied to alleviate the symptoms of hives.

People who frequently experience heat hives should take precautions to keep their body temperature within normal range. For instance, they should probably exercise in an air conditioned room, and keep plenty of cold liquids on hand to help keep their body temperature from rising. When showering or bathing, water temperature should be cool or warm. When heat exposure is unavoidable, people who suffer from heat hives should be sure they are dressed appropriately. Ideally, in these circumstances, clothing should be loose and designed for hot weather.

In some instances, heat hives can also be brought about by stress, anger, and depression. Since emotion does not generally cause sweat, the link between emotional response and heat hives is unclear. One of the reasons that research has not led to a definitive cause of heat related hives may be because the triggers for the condition can greatly vary.

In order to diagnose heat hives, doctors usually conduct skin allergy tests. This is done by applying a chemical called methacholine to a small area of the skin. Methacholine is believed to duplicate the allergic reaction that people typically have to heat. Though this type of testing is typical, the results are only accurate about 33% of the time.

Treatment for people who suffer from heat hives usually consists of antihistamines or steroids. Antihistamine is a type of allergy medication that inhibits the production of a chemical called histamine, which is believed to be responsible for allergic reactions. Steroid treatment is usually reserved for chronic conditions or for those who experience some of the more severe symptoms associated with heat hives.

Heat hives are usually diagnosed using a skin allergy test during which a small sample of methacholine is applied to the skin.
Heat hives are usually diagnosed using a skin allergy test during which a small sample of methacholine is applied to the skin.

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Discussion Comments


I'm not sure if I have an allergy to my sweat or to sunlight, but I always get hives when I'm out in the sun. I try to stay indoors and I use a lot of aloe vera gel. Aloe vera gel is very effective for heat rash symptoms.


@turquoise-- Heat hives in children is common. My son had it when he was a toddler too. The problem was that I was putting too many clothes on him thinking that he's going to get sick. But toddlers are active and he would soon sweat and break out in a rash on his neck and back.

I stopped putting layers on him and bought only 100% cotton clothes because cotton absorbs sweat. When he did get a heat rash, I applied calamine lotion. The problem went away on its own.


My six month old has heat induced hives. Whenever she gets a little hot, she starts crying and starts getting hives on her arms and legs. I remove her clothes right away but it takes a few hours for the hives to disappear. The doctor has given her children's antihistamine but I don't want her to have to use this constantly. I hope she grows out of it soon.

Has anyone experienced this with their children? Do you have any suggestions for me?

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