Also called urticaria
Hives are welts on the skin that often itch. These welts can appear on any part of the skin. Hives vary in size from as small as a pen tip to as large as a dinner plate. They may connect to form even larger welts.
A hive often goes away in 24 hours or less. New hives may appear as old ones fade, so hives may last for a few days or longer. A bout of hives usually lasts less than 6 weeks. These hives are called acute hives. If hives last more than 6 weeks, they are called chronic hives.
Acute hives often result from an allergy, but they can have many other causes.
The medical term for hives is urticaria (ur-tih-CAR-ee-uh). When large welts occur deeper under the skin, the medical term is angioedema (an-gee-oh-eh-dee-ma). This can occur with hives, and often causes the eyelids and lips to swell.
In severe cases, the throat and airway can swell, making breathing or swallowing difficult.
Hives: Signs and symptoms
The most common signs (what you see) of hives are:
As for symptoms (what you feel), hives usually itch. They sometimes sting or hurt.
Some people always get hives in the same spot or spots on their body. These people often have a trigger (what causes the hives). Every time they are exposed to that trigger, they get hives.
Your dermatologist may call this type of hives fixed, which means not moving. Fixed hives may happen when a person takes a certain medicine (fixed drug eruption) or gets too much sunlight (fixed solar urticaria).
Who gets hives?
Hives are common. Anyone can get them.
What causes hives?
An allergic reaction can trigger hives. Things that commonly trigger an allergic reaction include:
Other causes of hives are:
Hives can happen within minutes of exposure to the trigger. Or you can have a delayed reaction of more than two hours.
How do dermatologists diagnose hives?
When a patient has hives on the skin, a dermatologist can often make the diagnosis by looking at the skin. Finding the cause of hives, however, can sometimes be hard. This is especially true for hives that have been around for more than six weeks.
To find out what is causing your hives, your dermatologist will review your health history, ask questions, and do a physical exam. You may need the following tests:
To perform a skin biopsy, the dermatologist removes a small piece of affected skin so that it can be examined under a microscope.
How do dermatologists treat hives?
For a mild or moderate case of hives, the most common treatment is a non-sedating (does not cause drowsiness) antihistamine. Antihistamines relieve symptoms like itching.
If you have chronic hives, your dermatologist may prescribe an antihistamine. You should take this medicine every day to prevent hives from forming. There are many antihistamines on the market. Some make you drowsy, and some do not. No one antihistamine works for everyone. Your dermatologist may combine an antihistamine with other medicines to control the hives.
Other medicines that are prescribed to treat hives include:
Ask your dermatologist about possible side effects (health problems that can result from the medicines).
For some cases of hives or angioedema, you may need an injection of epinephrine (shot of adrenaline).
A hive often will go away in 24 hours or less, but bouts can last longer.
A few people have chronic hives (lasting more than six weeks). Sometimes chronic hives go away on their own — often within a year. For others, hives can come and go for months or years. Children may outgrow the allergies that cause their hives.
For most people, hives are not serious. In some people, though, hives may be a sign of an internal disease. Others can get a severe swelling with hives known as angioedema. If you have hives and trouble breathing or swallowing, get emergency care right away.
When hives are mild, you may not need treatment. You can often relieve the itching by placing cool cloths on the hives, or by taking cool showers.
The best remedy for hives is to try to avoid whatever triggers them.
If you have a bad allergic reaction, like shortness of breath, talk to your doctor about a prescription medicine called an “auto-injector.” This medicine stops the allergic reaction when you inject it into your thigh. Follow your doctor’s advice on how to use this medicine.
If allergies cause your hives, you can find support groups that help people living with allergies.
Allergy educational support groups
The Asthma and Allergy Foundation of America offers support groups for young people and adults and for parents of children with allergies.