These are sometimes confused with heat rash, or prickly heat. Although both conditions can cause a rash, the causes and the appearance of the rash are very different. Prickly heat causes a rash with small red spots as a result of blocked sweat glands.
Heat hives, also called cholinergic urticaria, is an allergic reaction caused by a rise in skin temperature. The rash can cover a small area on your body or can appear all over your body. It usually disappears once your body cools down.
Symptoms of heat hives include itchy skin, prickly, tingling, or burning sensation, flushing of the skin, rash, or raised welts. Some people find they do not sweat until after the hives have appeared.
Antihistamines can be used when necessary to control the hives. These are available over-the-counter; however, your doctor also can prescribe stronger antihistamines. When the hives are severe or do not disappear after your body cools, your doctor might prescribe steroids or corticosteroids.
Because heat hives are a result of your skin temperature rising, it is important to take steps to keep your skin cool.
Avoid taking hot showers. Opt instead for lukewarm water.
Avoid spending time outdoors when it is hot. It you do, keep ice packs, cooling sprays, or cool compresses with you to cool your skin.
Avoid alcoholic beverages, especially during the hot weather, as these can raise your body temperature and cause a flare up of your hives.
Wear clothing appropriate for the weather. Lightweight, cotton clothes in the warm months and wearing layers during the cold months so you can remove layers when you go into a heated environment can help.
Pay attention to other triggers, such as spicy foods, and take steps to avoid them.
If you notice a tingly or uncomfortable feeling on your skin, immediately take steps to cool your skin using cool water, going out in the cool air, or inside to an air conditioned environment to regulate your skin temperature.