Food allergies occur when your body mistakenly identifies and treats an ingested food as a threat, triggering an immune system response. Even eating a tiny amount of the offending food can lead to symptoms ranging from hives to swelling, stomach troubles to difficulty breathing, and even death. More than 90% of the most common food allergies are caused by one of eight allergens: dairy, eggs, wheat, soy, peanuts, tree nuts, fish, or shellfish.

Frequently Asked Questions

  • What's the best way to test for food allergies?

    Food allergies can be diagnosed via a combination of different methods: a blood test (IgE antibody test, known as immunoCAP or ELISA), a skin prick test, an elimination diet, or an oral challenge test. An oral challenge is often used when other testing is inconclusive, as it's the only test that can be used to actually confirm a food allergy, or to test if a food allergy has been outgrown.

  • What causes food allergies?

    Food allergies are caused by an immune system overreaction to a food the body has mistakenly deemed harmful. Experts aren't entirely sure why some people develop allergies and others don't. Environmental factors may play a role, as may family history. Having eczema, allergic rhinitis, or asthma makes you much more likely to have a food allergy, a phenomenon known as atopy.

  • Are food allergies genetic?

    Genetics seem to play a big role in the development of food allergies, as having a parent/sibling with a food allergy or atopy (allergic rhinitis, asthma, or eczema) can greatly increase your chances. But genetics aren't the only factor. Environmental triggers, such as where you live and the regional cuisines you regularly eat, are also a big component in development.

  • How long does an allergic reaction to food last?

    Allergic reactions may vary in length. Some allergic reactions may set in a few minutes after consuming the allergenic food, whereas others may appear up to two hours later. If hives or a rash develop, they may take a day or two to fully clear up. If you're experiencing any symptoms of anaphylaxis, such as throat constriction, dizziness, or shock, seek immediate medical help.

  • Can food allergies cause a fever?

    While food allergies can sometimes cause cold- and flu-like symptoms such as runny nose, sore throat, or sneezing, they do not typically cause a fever. Allergic rhinitis, also known as hay fever, is a common allergy, but it doesn't cause a fever.

  • Can food allergies cause acne?

    Food allergies are unlikely to cause acne, however, acne may be related to a food intolerance or sensitivity. A food intolerance is a condition in which the body has a reaction to a certain food, but the mechanism of this reaction is unknown and is not thought to be related to IgE that is involved in food allergies.

Key Terms

Page Sources
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  1. U.S. Department of Agriculture. Food allergies.

  2. American College of Allergy, Asthma, and Immunology. Food allergy diagnosis. Updated February 12, 2019.

  3. Weidinger S, Novak N. Atopic dermatitis. Lancet. 2016 Mar 12;387(10023):1109-22. doi:10.1016/S0140-6736(15)00149-X.

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