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Peanut Allergy

Topic Overview

What is a peanut allergy?

A peanut allergy is a reaction that occurs when your body mistakenly identifies peanuts as harmful substances. When you eat peanuts or food containing peanuts, your immune system—the body's natural defense system that fights infections and diseases—overreacts and can cause a serious, even life-threatening response.

What causes a peanut allergy?

An allergic reaction occurs when your immune system overreacts and releases chemicals, including histamine, into your blood. These chemicals can affect different tissues in the body, such as the skin, eyes, nose, airways, intestinal tract, lungs, and blood vessels. It's not clear why peanuts trigger this response in some people.

What are the symptoms?

Symptoms of peanut allergy can range from mild to life-threatening. If you have a mild reaction, you may get a stomachache, a runny nose, an itchy skin rash, hives, or tingling in your lips or tongue. If your reaction is worse, you may develop additional symptoms such as a tight throat, hoarse voice, wheezing, coughing, feeling sick to your stomach, vomiting, belly pain, and diarrhea. Your symptoms may start from within a few minutes to a few hours after eating peanuts or peanut products.

People who are allergic to peanuts may have a life-threatening reaction called anaphylaxis. Symptoms of anaphylaxis can include problems breathing and swallowing; vomiting and diarrhea; dizziness; dangerously low blood pressure; swelling of the lips, tongue, throat, and other parts of the body; and loss of consciousness. If not treated, death can result. Anaphylaxis usually occurs within minutes but can occur up to several hours after eating peanuts or peanut products.

How is a peanut allergy diagnosed?

To diagnose a peanut allergy, your doctor will start with a medical history and a physical exam. Your doctor will ask about any family food allergies, especially siblings with peanut allergies. He or she will ask detailed questions about your symptoms, how soon your symptoms began after you ate the food, and if any over-the-counter allergy medicines like an antihistamine were helpful. Your doctor will ask if other people also got sick, how the food was prepared, and what other foods were eaten.

It's important to find out whether you have a food allergy or food intolerance. Your doctor may ask you to keep a record of all the foods you eat and any reactions to the foods. Your doctor will also consider if your reaction could have been caused by things like allergies to medicines or insect stings, food poisoning, irritants in foods, and exposure to skin irritants.

Your doctor may ask you to try an elimination diet, an oral food allergy challenge, or both.

  • In an elimination diet, you avoid eating foods that may be causing an allergic reaction and see if your symptoms go away. If symptoms come back when you eat the food again, your doctor can confirm your food allergy. The elimination diet can last from 2 to 8 weeks.
  • In an oral food allergy challenge, you eat a variety of foods that may or may not cause an allergic reaction. Your doctor watches to see if and when a reaction occurs. This test is considered the best way to diagnose a food allergy.

You may also have allergy tests, such as skin tests or blood tests, to determine what foods you are allergic to after you have been diagnosed with having a food allergy.

How is it treated?

If you accidentally eat a peanut, follow your doctor's instructions. For a mild reaction, you may only need to take an antihistamine, such as diphenhydramine hydrochloride (Benadryl), to reduce your symptoms of a runny nose or itchy skin.

If your allergic reaction is more severe, be sure to follow your doctor's instructions for this type of reaction. If you have had a severe reaction previously, your doctor has probably prescribed a medicine called epinephrine. Give yourself the epinephrine shot, take an antihistamine, and call 911 for further instructions.

For more information on how to give an epinephrine shot, see:

Click here to view an Actionset. Allergies: Giving Yourself an Epinephrine Shot.
Click here to view an Actionset. Allergies in Children: Giving an Epinephrine Shot to a Child.

Even if you feel better after giving yourself the shot, symptoms of anaphylaxis can recur or suddenly appear hours later. You need to be observed in a hospital for several hours after your symptoms go away.

If you do not have epinephrine and are having a severe allergic reaction, call 911 immediately.

How can I avoid an allergic reaction?

To prevent an allergic reaction to peanuts:

  • Understand your allergy and know that you need to protect yourself. Read food labels or ask kitchen staff at restaurants if there are peanuts or peanut oils hidden in any of the foods you order. For example, some cooks thicken chili with peanut butter.
  • Some people are so severely allergic to peanuts that being near them or breathing air that contains peanut residue can cause an allergic reaction.
  • Let others know that you or your child has a peanut allergy. Make sure that all caregivers (such as school administrators, teachers, babysitters, and coaches), friends, and coworkers:
    • Know what the symptoms of an allergic reaction look like.
    • Know where the epinephrine shot is kept and how to give the shot.
    • Have a plan to transport you or your child to the hospital.
  • Wear a medical alert bracelet or medallion that lists your peanut allergy. This will alert emergency response workers if you have a severe allergic reaction. Medical alert jewelry can be ordered through most pharmacies or on the Internet.
  • Keep your epinephrine shot with you at all times. Make sure older children know how to give you or themselves the shot. Talk with your doctor or pharmacist if you are unsure how to give yourself the shot.
  • Keep an antihistamine such as diphenhydramine hydrochloride (Benadryl) with you at all times. These medicines can be used in addition to epinephrine and are often helpful in both mild and severe allergic reactions.

If you think you are having an allergic reaction:

  • Get help. Do not minimize the seriousness of the problem.
  • After you give yourself an epinephrine shot, call your doctor immediately or seek other emergency services. You will need to be observed for several hours to make sure the reaction does not recur.

Credits

By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer Rohit K Katial, MD - Allergy and Immunology
Last Revised August 14, 2013

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