Patient education: Peanut, tree nut, and seed allergy (The Basics)

What is a peanut, tree nut, or seed allergy? — A food allergy is when a person's immune system responds as if a certain food is harmful to the body. (The immune system is the body's infection-fighting system.)

Allergies to the following foods are common:

●Peanuts

●Tree nuts, such as walnuts, cashews, and hazelnuts

●Seeds, such as sesame, mustard, sunflower, and flax

Most often, allergic reactions happen from eating the food or something that contains the food. Less often, allergic reactions happen when a person breathes in tiny pieces or dust, like from a package of nuts. Touching the food can also cause a skin reaction.

What are the symptoms of an allergic reaction? — Common symptoms include:

●Hives, which are raised or puffy areas of skin that are itchy (picture 1)

●Puffiness of the face, eyelids, ears, mouth, hands, or feet

●Swelling of the tongue (picture 2)

●Trouble breathing, noisy breathing (wheezing), or coughing

●Nausea, vomiting, or diarrhea

●Feeling dizzy or passing out

●Death (although this is very rare)

The above symptoms usually start quickly, minutes to hours after eating the food. A severe allergic reaction is also called "anaphylaxis." When a person has anaphylaxis, they can get very sick, very quickly.

Although uncommon, a food allergy also sometimes triggers other symptoms. When this happens, it is usually hours to days after eating the food. These symptoms include:

●Eczema – This is a skin condition that makes the skin itchy and flaky.

●Eosinophilic esophagitis – This is a condition that makes it hard to swallow food or causes heartburn. It can happen in people who are allergic to peanuts or tree nuts.

Is there a test for a peanut, tree nut, or seed allergy? — Yes. Your doctor or nurse will ask about your symptoms and the foods you eat. They will also do a test to check for an allergy. Tests can include:

●A skin test – This involves pricking your skin with a device that contains a tiny amount of the nut or seed you might be allergic to. The test is positive if you get an itchy bump, like a mosquito bite, where your skin was pricked.

●Blood tests – These tests check the level of "IgE antibodies" in your blood. Antibodies are a type of protein. The body makes IgE antibodies when it is having an allergic reaction to something.

For peanuts and some tree nuts, different blood tests can be done. For example, 1 looks for IgE to whole peanut. Another test, called "component testing," looks for IgE to several different proteins found in peanuts. These test results can give your doctor more information about your allergy and how best to manage it.

Some people have a test called a "food challenge." This involves gradually eating a serving of the food and seeing whether it causes symptoms. For safety reasons, this test is done only in a doctor's office or hospital. Usually, a food challenge is only done if other tests are not clear, or if a doctor wants to check if a person's allergy has gone away.

Can peanut, tree nut, or seed allergy be cured? — As of now, there is no definite cure for a food allergy. A treatment called "oral immunotherapy" ("OIT") might lower the risk of an allergic reaction if a person is accidentally exposed to a food. This involves getting tiny amounts of the food in a controlled way. OIT comes with risks and is not likely to make an allergy go away completely. But it might be an option in certain situations.

How are allergic reactions treated? — Severe allergic reactions are usually treated with medicine called epinephrine. Epinephrine comes in a device called an "autoinjector." This device gives you a shot of epinephrine (picture 3). When your doctor prescribes an autoinjector, they will show you how to use it and give you instructions for when to use it. Keep your autoinjector with you at all times. Most doctors recommend carrying 2 autoinjectors in case you need a second dose.

After you use an autoinjector, call for an ambulance (in the US and Canada, call 9-1-1). Epinephrine doesn't last very long in the body, and symptoms can sometimes come back as it wears off. In the hospital, doctors can watch you and give you more medicine if needed.

If you think that someone is having a severe allergic reaction and you do not have an epinephrine autoinjector, call for emergency medical help right away.

How can I prevent an allergic reaction? — The only way to prevent an allergic reaction is to completely avoid eating the food you are allergic to.

●To know whether a food contains peanuts, tree nuts, or certain seeds, you need to read its ingredient label. Some countries (including the US) have laws that make companies clearly list whether a food has certain common "allergens" in it. These include peanuts, tree nuts, and sesame.

●Some foods have warning labels for food allergies, such as "May contain peanuts or tree nuts." These foods might have been made on machines or in factories that also made other foods with nuts. Talk to your doctor about whether you should avoid these foods.

●Foods that are especially likely to contain peanuts, tree nuts, or seeds include baked goods and Asian, African, and Mexican foods. If you eat at a restaurant, bakery, or ice cream parlor, tell your server about your allergy.

What else should I know if I have a peanut, tree nut, or seed allergy? — People with an allergy:

●Can have an allergic reaction if they share saliva with (kiss) someone who ate the food and did not brush their teeth afterward

●Cannot have an allergic reaction by only smelling a nut or seed butter

●Might have an allergic reaction by breathing in dust or tiny bits of the food, for example, when someone cooks with nuts or seeds (if they are very allergic)

●Might get hives on their skin if they touch the food they are allergic to

●Sometimes have allergies to other foods, too, so might need to avoid eating certain other foods

What if my child has a peanut, tree nut, or seed allergy? — If your child has an allergy, tell their caregivers, schools, and camps. You should:

●Tell them which foods your child can and can't eat.

●Make a plan so they know how to treat an allergic reaction.

●Make sure that they know where your child's epinephrine autoinjector is, and how and when to use it.

●Make sure that they know how to reach you or your child's doctor in case of an emergency.

Will my child outgrow their allergy? — Most children do not outgrow peanut, tree nut, or seed allergy, but some do. Your child's doctor will monitor your child's allergy over time to see whether they outgrow it.

Where can I learn more? — You can get more information about food allergies from an organization called Food Allergy Research & Education (FARE). Their website is www.foodallergy.org.

More on this topic

Patient education: Food allergy (The Basics)
Patient education: Anaphylaxis (The Basics)
Patient education: Angioedema (The Basics)
Patient education: How to use an epinephrine autoinjector (The Basics)
Patient education: Hives (The Basics)
Patient education: Eczema (atopic dermatitis) (The Basics)
Patient education: Eosinophilic esophagitis (The Basics)

Patient education: Food allergy symptoms and diagnosis (Beyond the Basics)
Patient education: Anaphylaxis symptoms and diagnosis (Beyond the Basics)
Patient education: Using an epinephrine autoinjector (Beyond the Basics)
Patient education: Eczema (atopic dermatitis) (Beyond the Basics)