While you may think of hives as resulting from an allergic reaction, they can also be caused by heat. These are called heat hives, or cholinergic urticaria.
In some people, a rise in temperature can produce the chemical histamine, similar to what happens when your immune system fights allergies. Histamine dilates blood vessels and results in swelling.
Other potential triggers for hives include:
- food allergies
- insect bites
- skin scratches
Causes and symptoms of heat hives
If you notice hives tend to break out when your body temperature rises, it may be a sign that heat is a trigger for your hives.
A 2014 study on cholinergic urticaria of 92 males in Korea identified several aggravating factors for the condition:
- hot or spicy foods
- psychological stress
The symptoms of heat hives are similar to hives caused by other triggers: red, itchy welts that can range in size from less than half an inch up to several inches in diameter.
Most cases of hives caused by heat appear within an hour after exposure.
Treatment and prevention
Many cases of heat hives fade on their own within 24 hours, but certain home remedies, prescription medications, and prevention techniques can ease symptoms and alleviate flare-ups.
After determining the specific causes of your symptoms and ruling out the possibility of a more serious underlying condition, your doctor might recommend an antihistamine, such as:
- fexofenadine (Allegra)
- desloratadine (Clarinex)
- loratadine (Claritin)
Home remedies include aloe vera, calamine lotion, and an oatmeal bath. These can:
- soothe your skin
- reduce swelling
- reduce symptoms
Prior to topical applications of this sort, check the ingredients to make sure that you aren’t allergic to any of them.
If over-the-counter (OTC) medication or home remedies don’t work, your doctor may recommend:
- histamine blockers
- anti-inflammatory medication
- drugs that suppress your immune system
You can also take a few precautions to help prevent heat hives:
- Try to keep cool while exercising.
- Prevent exposure to areas of high humidity.
- Avoid prolonged periods of direct sunlight exposure.
Heat rash vs. hives
Heat hives share similar causes and symptoms with many forms of heat rash.
Heat rash occurs when perspiration is trapped under your skin by blocked pores. Causes include humid weather, physical activity, or other factors that lead to a rise in the temperature of your body.
While heat rash tends to fade on its own, consider visiting your doctor for more severe or persistent cases. Your doctor can provide a proper diagnosis and help you determine whether you’re experiencing hives or heat rash.
Most instances of heat hives can be treated at home and eventually fade on their own. However, you should seek immediate medical attention if swelling occurs in your throat that makes it difficult to breath.
You and your doctor can work to identify the specific triggers of your heat hives and develop a prevention plan with ways to ease symptoms if flare-ups do occur.
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