Peanut Allergy

Condition Basics

What is a peanut allergy?

A peanut allergy is a reaction that occurs when your body mistakenly identifies peanuts as a harmful substance. When you eat peanuts or food that contains peanuts, your body's immune system overreacts. This can cause a serious response and even can cause death.

What causes it?

It's not clear why peanuts trigger a reaction in some people. 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. These include the skin, eyes, nose, airways, intestinal tract, lungs, and blood vessels.

What are the symptoms?


  • A stomachache.
  • A runny nose.
  • Itchy eyes.
  • Hives.
  • Tingling in your lips or tongue.


People who are allergic to peanuts may have a dangerous 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.
  • Loss of consciousness.

Anaphylaxis can cause death if not treated. It usually occurs within minutes but can occur up to several hours after eating peanuts or peanut products.

How is it diagnosed?

To diagnose a peanut allergy, your doctor will start with a medical history and a physical exam. Your doctor will want to know about any family food allergies, especially siblings with peanut allergies. Your doctor will ask about your symptoms and how soon they started after you ate the food. He or she will ask if any over-the-counter allergy medicines like an antihistamine were helpful. Your doctor will also ask if other people 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. You may be asked 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 or an oral food allergy challenge. Or the doctor may have you try 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. This diet can last from 2 to 8 weeks.

You may also have allergy tests, such as skin tests or blood tests. These help to find out what foods you are allergic to after you've been diagnosed with having a food allergy.

How is an allergic reaction to peanuts treated?

If you by accident eat a peanut or food that contains peanuts, follow your doctor's instructions.

If you had a severe reaction in the past, your doctor probably prescribed a medicine called epinephrine. If you have symptoms in more than one body area, such as mild nausea and an itchy mouth, give yourself an epinephrine shot. Then call 911.

Even if you feel better after giving yourself the shot, symptoms of anaphylaxis can recur or suddenly appear hours later. You will need to be watched 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 right away.

How can you prevent it?

This is how to prevent an allergic reaction to peanuts.

  • Understand your allergy.

    Be aware 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.



    • Know what the symptoms of an allergic reaction look like.
  • Wear a medical alert bracelet or medallion that lists your allergy.


  • Keep your epinephrine shot with you at all times.


  • Keep other medicines with you if your doctor recommends it.

    This includes antihistamines used for mild reactions. Antihistamines are not a substitute for epinephrine in a severe allergic reaction.

If you think you are having an allergic reaction, get help. Do not minimize how serious this problem is. 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.

Related Information


Current as of: February 10, 2021

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine

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