A food allergy, or hypersensitivity, is an abnormal response to a food that is triggered by the immune system. The immune system is not responsible for the symptoms of food intolerance, even though these symptoms can resemble those of a food allergy. For example, being allergic to milk is different from not being able to digest it properly due to lactose intolerance. There are two main ways that a food can cause bothersome physical symptoms. The first category is what we call food hypersensitivity.

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These reactions occur when your immune system responds abnormally to proteins in specific foods. These immunologic reactions may be caused by IgE antibodies, which we refer to as a food allergy, or may be related to mechanisms that do not involve IgE. Patients with food allergy due to IgE antibodies often have gastrointestinal symptoms (nausea, vomiting, diarrhea, and abdominal cramping), skin reactions (hives and eczema), and full-blown systemic reactions, also called “anaphylaxis” (throat swelling, wheezing, and drop in blood pressure). Food hypersensitivity that is not related to IgE antibodies includes a number of relatively rare disorders, such as food-induced enter colitis (inflammation of the colon) and celiac disease (immune reaction to gluten).

The second large category of reactions is referred to as food intolerance reactions. These adverse responses to foods are relatively common and are not related to any immunologic mechanism. A good example is lactose intolerance.

Which Food Allergies Are Most Common?

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Peanuts, soybeans, tree nuts, eggs, cow’s milk, wheat, shellfish, and fish are the most commonly reported allergenic foods. Allergy to peanuts, soy, tree nuts, eggs, milk, or wheat often develop early in the first few years of life, while hypersensitivity to shellfish or fish more often manifests in adulthood. Allergy to milk or eggs frequently resolves between age 3 and 5 years, while allergy to peanut, tree nuts, shellfish, or fish often lasts through a patient’s lifetime.

Treatment for Food Allergies

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Several important steps can protect a patient with serious food allergies from having future reactions. These steps include:

  1. Remove all sources of food that the patient is allergic to. Even trace amounts of a food protein can cause a severe reaction in some people. It can be particularly challenging to avoid foods that frequently show up in food items as hidden ingredients, such as peanuts.
  2. Be careful when dining out. Most inadvertent exposures to allergenic foods occur while eating in restaurants or in friends’ homes.
  3. Do not eat foods with an unknown list of ingredients. For children with food allergies, it is very important to make all lunches and snacks that are taken to school or any outing away from home.
  4. Wear a Medic-Alert bracelet to identify yourself as having a life-threatening allergy to food.
  5. Epinephrine is the single most important treatment for food-induced anaphylaxis. People with histories of systemic reactions to foods should have epinephrine available at all times, including in their backpack or purse, home, school nursing office, and car(s).