What are hives?
Hives are raised bumps caused by irritation in the upper layers of the skin. They can be pale, pink, or red and are very itchy. The bumps are often oval or round, but also can be other shapes. They are usually 1 to 2 cm in size (about the size of a quarter), but can be larger or smaller. They may combine with nearby hives as they grow to form larger hives. Hives sometimes occur with inflammation in deeper layers of the skin, which causes swelling and can be painful. The medical term for hives is urticaria (UR-tih-CAR-ee-uh).
Usually hives only affect the skin, but sometimes they can be part of a bad allergic reaction affecting many body parts. When this happens, you may have dizziness, stomach cramps, swelling, or trouble breathing. If you think you are having a bad allergic reaction, go to the emergency room.
How long do they last?
Hives show up quickly (within minutes) and fade within hours. After they fade, there are no marks other than scratches from itching. But, new hives may show up after the original hives have gone away. For most people, the hives will come back for only a few days or at most a few weeks. In some people, hives may come back every day or every few days for months to years. This is called chronic hives.
Who gets them?
People of all ages can get hives. About one in five people will have hives at some point in his or her life, but about one in 20 people will have episodes that last more than six weeks (chronic hives).
What causes them?
Hives can be caused by many things, including:
Bladder infections or other types of infection
Allergies to food, particles in the air, or things that touch your skin
Insect stings or bites
Heat, cold, or pressure
A serious disease, but this is uncommon In many cases, no specific cause is found.
How are they diagnosed?
Your doctor can diagnose hives by looking at the skin, asking questions about possible triggers, and doing an exam. Because hives can fade by the time you see your doctor, it may help to take a picture of them. Blood tests usually are not needed unless the hives have been coming back regularly for more than six weeks. Other testing may be done if your doctor thinks a specific cause is likely.
How are they treated?
The most important treatment is avoiding the things that cause your hives, if your doctor finds out what is causing them. Your doctor may have you take medicines called antihistamines, if needed. You can get many of these without a prescription. Sometimes your doctor may have you take more than the normally recommended dose, but this should only be done under supervision. Sometimes other prescription medicines also are used to treat hives.
Where can I get more information?
AAFP's Patient Information Resource
https://familydoctor.org/familydoctor/en/diseases-conditions/exercise-induced-urticaria.html (for urticaria caused by exercise)
American Academy of Dermatology
NIH National Library of Medicine