Daniel More, MD, is a board-certified allergist and clinical immunologist with a background in internal medicine.
Food allergies occur when your body mistakenly identifies and treats an ingested food as a threat, initiating an immune system response. Even eating a tiny amount of the offending food can trigger an allergic reaction, which may involve anything from hives to eczema, stomach troubles to difficulty breathing, and even death.
Some allergies may be lifelong, while others may fade over time. 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.
Overall, food allergies are relatively common, impacting 32 million Americans, including 5.6 million children under the age of 18. While food allergies tend to run in families, doctors are not able to predict who will develop food allergies and who will not.
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.
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.
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.
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.
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.
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 not an immune response.
A sudden and severe whole-body allergic reaction resulting in a significant drop in blood pressure, the onset of shock, and shortness of breath. Anaphylaxis occurs as the result of an allergy affecting more than one body system at the same time, such as the skin and respiratory systems. Anaphylaxis comes on quickly and is a medical emergency requiring immediate care.
Also known as atopic eczema, atopic dermatitis is an inflammatory skin condition marked by a dry, itchy, inflamed rash that may be acute or chronic. Eczema has many potential causes, including genetics and environmental factors. Food allergens are a common trigger of atopic dermatitis.
Not a true allergic reaction, histamine intolerance is a response to certain foods that contain high levels of histamine, a naturally occurring chemical. Histamine can be found in alcohol, aged cheeses, and other fermented foods, as well as spinach and tomatoes. Migraine headaches are a classic symptom of histamine intolerance
The body's defense system to protect you from infection and harmful microorganisms. The immune system is capable of waging complex responses to various viruses, bacteria, and pathogens, but in some cases, a certain trigger may set off an immune reaction when one is not warranted, as in the case of food allergies.
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