Hives

Hives: An allergy to a medicine can cause hives.

Hives: Overview

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-CARE-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.

If this occurs, the person needs emergency care right away.

Image used with permission of the American Academy of Dermatology National Library of Dermatologic Teaching Slides.

Hives: This patient has widespread, raised welts.

Hives: Signs and symptoms

The most common signs (what you see) of hives are:

• Slightly raised, pink or red swellings .
• Welts that occur alone or in a group, or connect over a large area.
• Skin swelling that subsides or goes away within 24 hours at 1 spot but may appear at another spot

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.

Hives: This 4-year-old child developed hives after getting bit by mosquitoes.

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).

Images used with permission of the American Academy of Dermatology National Library of Dermatologic Teaching Slides.

Hives: Who gets and causes

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:

• Foods: Fruits (especially citrus fruits), milk, eggs, peanuts, tree nuts, and shellfish.
• Medicines.
• Insect bites and stings.
• Animals.
• Pollen.
• Touching something to which you are allergic, such as latex.
• Allergy shots.

Other causes of hives are:

• Infections, including colds and infections caused by some bacteria or fungi.
• Some illnesses, including a type of vasculitis, lupus, and thyroid disease.
• Exposure to sun (solar urticaria), heat, cold, or water.
• Exercise.
• Stress.
• Pressure on the skin, such as from sitting too long.
• Contact with chemicals.
• Scratching the skin.

Hives can happen within minutes of exposure to the trigger. Or you can have a delayed reaction of more than two hours.

Hives: Diagnosis and treatment

How do dermatologists diagnose hives?

When a patient has hives, a dermatologist can often make the diagnosis by looking at the skin. Finding the cause of hives, however, can be a challenge. This is especially true for hives that have been around for more than 6 weeks.

To find out what is causing your hives, a dermatologist will review your health history, ask questions, and do a physical exam. You may also need the following tests:

• Allergy tests (on the skin or blood tests).
• Blood work (to rule out an illness or infection).
• A skin biopsy.

To perform a skin biopsy, your 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.

Antihistamines are also prescribed to treat chronic (lasting longer than 6 weeks) hives. When prescribed for chronic hives, you 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.

Medicines that dermatologists prescribe to treat hives include:

• Antihistamines
• Corticosteroids like prednisone
  These are prescribed for short-term use due to side effects with long-term use.
• Dapsone
  This isan antibiotic that can also relieve redness and swelling
• Omalizumab
  This injectable medicine can help patients with chronic idiopathic urticaria (CIU), a type of hives that can last for months — or even years.
• Other medicines that fight inflammation (redness and swelling).

Ask your dermatologist about possible side effects (health problems that can result from the medicines).

For some cases of hives or angioedema (a condition similar to hives, but the swelling occurs deeper in the skin), you may need an injection of epinephrine (shot of adrenaline).

All medicines have possible side effects. Be sure to ask your dermatologist about possible side effects (health problems that can result from the medicines).

Treatment for chronic hives

To treat a type of chronic hives called CIU, which can last for 6 weeks or longer and sometimes years, the U.S. Food and Drug Administration has approved 2 medications — antihistamines and omalizumab.

Research shows that up to 50% of people with CIU continue to have hives after treatment with antihistamines. Omalizumab, which is injected under the skin, has been shown to relieve the itch and clear hives in some people with CIU. In one research study, 36% of patients treated with omalizumab reported no itch and no hives after treatment.

Outcome

For most people, hives are not serious. Children may outgrow the allergies that cause their hives.

Some people with chronic (lasting more than 6 weeks) hives, see the hives go away on their own — often within a year. For many people with a chronic case, however, the hives come and go for months or years.

If the hives remain or becomes severe, it’s important to get medical care. Hives can be a sign of an internal disease. Some people develop severe swelling .

If you have hives and trouble breathing or swallowing, get emergency care right away.

Hives: Tips for managing

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.

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.

Related resources:

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.

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