Food Allergy

What is a food allergy?

A food allergy is when your immune system has a bad reaction to a certain food. This is different from a food intolerance, which does not involve the immune system. This is true even though some of the same signs may be present.

What causes a food allergy?

Your body’s immune system fights off infections and other dangers to keep you healthy. When your immune system senses that a food or something in a food is a danger to your health, you may have a food allergy reaction. Your immune system makes IgE (immunoglobulin E) antibodies. These react to the food or substance in the food. This causes your body to release histamine and many other substances. This can cause hives, asthma, itching in the mouth, trouble breathing, stomach pains, vomiting, or diarrhea. It doesn't take much of the food to cause a severe reaction in highly allergic people.

Most food allergies are caused by these foods:

  • Milk

  • Eggs

  • Wheat

  • Soy

  • Tree nuts

  • Peanuts

  • Fish

  • Shellfish

  • Sesame

Food protein-induced enterocolitis syndrome (FPIES) is also called the delayed food allergy. FPIES is rare and usually occurs in young babies. It causes vomiting and severe fluid loss (dehydration) hours after eating a food. The most common cause of FPIES is having milk, soy, or grains. FPIES is not caused by IgE antibodies.

What are the symptoms of a food allergy?

Allergic symptoms may begin within minutes to an hour after eating the food. Symptoms may be a bit different for each person. Symptoms may include:

  • Severe nausea or vomiting

  • Diarrhea

  • Stomach cramps or stomach pain

  • Red, itchy rash (hives)

  • Face swelling

  • Eczema

  • Itching or swelling of the lips, tongue, or mouth

  • Throat itching or tightness

  • Feeling dizzy with a lowered blood pressure

  • Asthma symptoms, such as coughing, runny or stuffy nose, wheezing, or trouble breathing

The symptoms of a food allergy may look like other health problems. Always see your healthcare provider for a diagnosis.

Severe symptoms of a food allergy

Anaphylaxis is a severe allergic reaction. It is life-threatening. Symptoms can include:

  • Trouble breathing, shortness of breath, or wheezing

  • Feeling as if the throat is closing

  • Hoarseness or trouble talking

  • Swelling of the face, lips, tongue, and throat

  • Cool, moist, or pale blue skin

  • Feeling faint, dizzy, lightheaded, or confused (this could be from a drop in blood pressure)

  • Nausea, belly (abdominal) pain, vomiting, or diarrhea

  • Fast and weak heartbeat

  • Loss of consciousness

  • Seizure

When to call 911

Anaphylaxis is a medical emergency. Call 911 to get help right away. Severe allergic reactions are treated with epinephrine. You should carry an emergency kit with self-injecting epinephrine. If you have emergency injectable epinephrine, use it before you call 911.

How is a food allergy diagnosed?

If you think you have a food allergy, see your healthcare provider for a diagnosis. They will take your health history and do a physical exam. The healthcare provider will do skin or blood tests or both to find out the exact diagnosis. These tests may include:

  • Skin prick test

  • Blood test

  • Oral food challenge

  • Trial elimination diet

How is a food allergy treated?

There is currently no cure for food allergy. You need to stay away from the food that causes the symptoms. This includes speaking up when you are at a restaurant or at friends' homes. Let them know that you have a food allergy. Don't be shy. And be clear that you could have a severe reaction if you eat a food you are allergic to, even in small amounts.

The FDA recently approved a medicine called omalizumab to help reduce a person's allergic reaction to food if they are accidentally exposed. It may be helpful for several different types of food allergies. Omalizumab is a monoclonal antibody that is given as an injection. It is approved for adults and children over 1 year old. People who take this medicine should still avoid the foods they are allergic to. Talk to your provider to see if this medicine is an option for you.

A different medicine is available to reduce the risk of allergic reactions in children with a peanut allergy. The FDA-approved oral immunotherapy (OIT) medicine is for children and teens ages 4 to 17. A child with a confirmed peanut allergy can start taking the medicine at age 4. Talk with your child’s healthcare provider to find out if this medicine can help your child. If your child is taking this medicine, you should still make sure they don’t eat peanuts or peanut products.

If you have a food allergy, carry an epinephrine autoinjector to treat emergency reactions. Know how to give yourself this medicine. You must be ready to treat any allergic reaction caused by eating a food by mistake that you are sensitive to. You need an emergency kit to stop severe reactions. Talk with your healthcare provider about how to use it. Also consider wearing a medical alert bracelet or necklace

Medicines are available to treat some symptoms of food allergy after the food has been eaten. These medicines may ease nose and sinus symptoms, digestive symptoms, or asthma symptoms.

Living with a food allergy

If you have 1 or more food allergies, eating out can be a challenge. But it's possible to have a healthy and satisfying meal when dining out. It just means that you may have to plan ahead when you eat out.

Here are some tips for dealing with food allergies when you are eating away from home:

  • Know what ingredients are in the foods at the restaurant where you plan to eat. When possible, get a menu from the restaurant ahead of time and look over the menu items.

  • Let your server know from the start about your food allergy. Before you order, ask how the dish is made and what is in it. If your server does not know this information or seems unsure, ask to speak to the manager or the chef.

  • Don't go to buffet-style or family-style restaurants. There may be cross-contamination of foods from using the same utensils for different dishes.

  • Don't eat fried foods. The same oil may be used to fry several different types of foods, such as fish.

  • Carry your emergency injectable epinephrine whenever you go out to eat. Bring it to restaurants and to other people's homes.

Another tip for dining out is to carry a food allergy card. You can give it to your server or the manager before you order food. A food allergy card contains information about the specific items you are allergic to. It also has more information. This includes a reminder to make sure all utensils and equipment used to make your meal are thoroughly cleaned before use. You can easily print these cards yourself using a computer and printer.

Clearer food labels with FALCPA

The Food Allergen Labeling Consumer Protection Act (FALCPA) was passed into law in 2004. It helps make sure that labeling of food by manufacturers is clear. Here is more information about FALCPA:

Key points about a food allergy

  • A food allergy is when your immune system has a bad reaction to a certain food. Before having a food allergy reaction, a sensitive person must be exposed to the food at least once before.

  • Most allergies are caused by milk, eggs, wheat, soy, tree nuts, peanuts, fish, shellfish, and sesame.

  • Allergic symptoms may begin within minutes to an hour after eating the food. If you think you have a food allergy, see a healthcare provider for a diagnosis.

  • Carry an epinephrine autoinjector to treat emergency reactions. Know how to give yourself this shot.

  • The goal of treatment is to stay away from the food that causes the symptoms. Medicines may be an option to reduce allergic reactions in certain people.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • Bring someone with you to help you ask questions and remember what your provider tells you.

  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

  • Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

  • Ask if your condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if you do not take the medicine or have the test or procedure.

  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your provider if you have questions.

Online Medical Reviewer: Dan Brennan MD
Online Medical Reviewer: Deborah Pedersen MD
Online Medical Reviewer: Jessica Gotwals RN BSN MPH
Date Last Reviewed: 3/1/2023
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