Hives are raised, red, itchy areas on the skin (also called wheals or welts) that can result from an allergic reaction.
The medical term for hives is urticaria.
Clusters of hives may appear as a reaction to an allergen such as food, medicine, or an insect bite or sting. Hives may also occur as a reaction to infection or emotional stress. Histamine, a chemical your body makes, is released in response to the irritant that causes the hives to form. Histamine causes the redness, swelling, and itching. Often the cause of the hives cannot be determined.
The raised, red, itchy areas may vary in size and shape. You may have one or many hives. The hives may appear on any part of the body. They are most common on the arms, legs, and trunk. You may have red blotches on your face. The rash may last for a few minutes or several days. Hives can be uncomfortable and they may recur.
In the case of a severe reaction—to a bee sting, for example—your face and throat may swell. Rarely, hives may cause problems with breathing, creating the danger of a severe asthma attack or a closing of the throat from swelling, which can be life-threatening.
Your healthcare provider will look at the hives and ask about your history of sensitivity to such things as:
To find the cause of your hives, the healthcare provider may suggest that you:
It is easiest to identify drugs, foods, or plants that may cause you to have hives because the reaction usually happens within minutes or an hour. Identifying triggers such as emotional stress or multiple allergies may take more time. Identifying multiple allergies may require skin tests or other types of allergy tests.
The treatment your healthcare provider recommends will depend on how serious your hives are. He or she may suggest that you do one or more of the following to relieve the itching and reduce the swelling:
If the rash is severe or not responding to the above treatments, your provider may prescribe an oral steroid medicine (for example, prednisone) to take for a few days. Using a steroid for a long time can have serious side effects. Take steroid medicine exactly as your healthcare provider prescribes. Don’t take more or less of it than prescribed by your provider and don’t take it longer than prescribed. Don’t stop taking a steroid without your provider's approval. You may have to lower your dosage slowly before stopping it.
Hives rarely cause emergencies. But sometimes they can cause throat swelling and trouble breathing. If your throat is swelling or you are having trouble breathing or are wheezing, call 911. Once you are getting medical care, you will be given a shot of epinephrine (adrenaline) to stop the reaction. When the emergency symptoms have been treated, you will probably be given steroid medicine to take for the next several days to make sure the hives go away completely.
Once the hives have gone and you are feeling better, you should see your healthcare provider to talk about whether you need tests to find what caused the hives. If you are able to find the cause, the best prevention is avoiding the cause, if that’s possible. Whether you are able to learn the cause or not, if hives are a frequent problem, you may need to take antihistamines every day to keep from getting them again. If you had a severe reaction, with throat swelling and trouble breathing, you should ask your healthcare provider if you need an emergency epinephrine kit. This medicine kit lets you or a family member give you a shot of epinephrine if you start having a severe reaction and are waiting for medical help to arrive.
The itching, swelling, and redness of hives can last hours to several weeks or months. In most cases the hives eventually go away without treatment, but taking drugs such as antihistamines or a steroid help the hives go away faster. The medicines also treat the itching and usually prevent new hives.
Chronic hives last a longer time. Often it’s not possible to find their cause. The hives may go away on their own after weeks or months, but they may come back repeatedly. This can be very frustrating and very uncomfortable. It is important to see your healthcare provider for follow-up so you can let your provider know what is or isn’t working. It’s also important to make sure there is no underlying cause, such as infection, but most of the time there is no explanation for the repeated hives.
If you know the cause of your hives, you should take steps to avoid the cause. You may need to take frequent, even daily, doses of antihistamine to prevent recurrences.
