What are hives?

Hives are raised, red, itchy areas on the skin (also called wheals or welts).

What is the cause?

Many things can cause hives, such as:

• Allergies to:
  • Latex (a liquid from rubber trees that is used in many products, like gloves and toys)
  • Medicines
  • Insect stings
  • Foods, such as shellfish, eggs, milk, nuts, and peanuts
  • Chemical irritants, such as nickel, dyes in fabric, or cleaning products
• Poison oak, poison ivy, or poison sumac
• Infections
• Exercise
• Heat, cold, or pressure
• Stress
• An autoimmune disease, which is a disease that causes your body to mistakenly attack your own tissue, such as lupus

It is not known why some people develop hives and others do not.

What are the symptoms?

The raised, red, itchy areas may vary in size and shape. You may have one or many hives on any part of your body. They are most common on the arms, legs, face, or trunk. The rash may start within minutes or hours of coming in contact with the allergen. Hives can be uncomfortable and they may go away and then come back.

Sometimes, hives may also be a sign of a severe allergic reaction. With a severe reaction, you may also have swelling of your tongue and throat, wheezing, or trouble breathing.

How is it diagnosed?

Your healthcare provider will ask about your symptoms and medical history and examine you.

If you provider suspects that your hives are caused by an allergy, he may recommend that you keep a detailed diary for 2 to 4 weeks. Record everything you eat, drink, take as medicine, or are exposed to. You may need to remove certain foods from your diet, one at a time, to find the cause of hives. In some cases, it may take time to find the cause.

Tests may include:

• Blood tests
• A skin prick test, which uses a drop of allergen extract (liquid) put under your skin using a needle
• Elimination diet, which means you avoid eating certain foods for a few weeks to see if allergy symptoms go away
• Food challenge test, which is eating food that is a possible allergen to see if you have a reaction. This test is done only by a healthcare provider who is ready to treat you if you have a serious reaction to the food.

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 other types of allergy tests.

How is it treated?

Treatment will depend on how serious your hives are. 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. Several kinds of medicines may be used to treat hives:

• Antihistamines may be given to block the effect of histamine. Histamine is a chemical your body makes when you have an allergic reaction. Do not give antihistamines to children under the age of 4. If your child is between the ages of 4 and 6, ask your healthcare provider before giving antihistamines.
• If the hives are severe or do not respond to other treatments, your provider may give you steroid pills. Steroids help to lessen irritation and swelling in your body. By lessening the swelling, you will have fewer symptoms and be able to breathe better. 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.

A severe allergic reaction is life-threatening and usually needs to be treated with epinephrine. Epinephrine relaxes the muscles in your airways and throughout your body. It is usually given as a shot. You may need more than one shot to decrease your symptoms. If you are known to have a serious reaction, your provider may want you to carry an emergency kit. You or someone with you can give you the shot. Whether or not you have epinephrine, call 911 or your local emergency services right away for all severe allergic reactions.

How can I take care of myself?

Follow the full course of treatment prescribed by your healthcare provider. In addition:

• Avoid food or triggers that cause you to break out in hives.
• For relief from itching, you can:
  • Keep the area moist and cool. A cool washcloth works well.
  • Soak in a lukewarm bath with cornstarch (1/2 cup) or an oatmeal product made for skin conditions (available at drugstores) added to the water to help ease the itching.
  • Try a nonprescription antihistamine pill or cream, such as Benadryl, especially at bedtime if itching keeps you awake at night. Use it according to the package instructions. Do not use antihistamine pills and creams at the same time.
  • Keep your fingernails short and wear gloves at night to keep from injuring the skin by scratching.
  • Wear loose-fitting cotton clothing. Avoid scratchy clothing.
  • Avoid getting hot and sweaty.
• If you were prescribed an emergency kit, carry it at all times. Use it as directed by your provider. Check the expiration date for the medicine and replace it as needed to make sure it will work.
• Wear a medical alert bracelet or necklace that warns of your allergy and tells what to do in case of an emergency. Teach family members and coworkers how to help you if you have a severe reaction.

Ask your provider:

• How and when you will hear your test results
• If there are activities you should avoid and when you can return to your normal activities
• How to take care of yourself at home
• What symptoms or problems you should watch for and what to do if you have them

Make sure you know when you should come back for a checkup. Keep all appointments for provider visits or tests.

How can I help prevent hives?

If you know what caused your hives, try to avoid it. Your provider may suggest that you take antihistamines regularly to prevent hives.