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, abdominal 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 difficulty 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?

Your doctor or allergy specialist will ask you about your previous reactions to peanuts or peanut products, such as how long it took to develop symptoms after eating peanuts, and whether any of your family members have allergies or conditions like asthma. Next, the allergy specialist will do a skin test to see if you have an allergic reaction. During a skin test, a tiny bit of your skin will be pricked, and a small amount of peanut liquid will be placed on your skin. If you develop a skin rash or red bumps in that area of your skin, it is likely you are allergic to peanuts.

You may also need to have a blood test that will show whether your body has made proteins called antibodies that would cause an allergic reaction when you eat peanuts. One such test is called an ELISA test, and another is called a RAST test.

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.