Food Allergy—When the Immune System Takes Over

image for food allergy articleA food allergy is an overreaction of the immune system to a food or part of food. It may lead to upset stomach, rash, or wheezing. It may also cause dangerous swelling in airways known as anaphylaxis. The reaction will be the same anytime the food or food part is eaten.

Allergic Reaction Causes

Allergens are items that cause an unusual reaction for some people but not all. The immune system sees the allergen as a problem. After the first contact, it creates antibodies that see the food as a problem. The next time a person eats it, these antibodies will attach to the food and send signals. It starts a process to defend the body when it is not needed. It is not clear why this happens. The reaction causes swelling, irritation, and other symptoms. It may affect the skin, stomach, intestines, or airways.

People may react to one or more allergens. Common ones are:

  • Cow's milk
  • Eggs
  • Shellfish (shrimp, crab, or lobster)
  • Peanuts
  • Tree nuts (walnuts, cashews, Brazil nuts)
  • Fish
  • Soy
  • Wheat
  • Sesame seeds

Oral allergy syndrome is a type of food allergy that is common in people who also have hay fever. Some fruits and veggies have proteins that are like those found in common pollens. The body reacts to these proteins the same way it reacts to pollen. It may lead to tingling or itching in the mouth when eating certain foods. This kind of allergy can also have more serious and life-threatening reactions.

Food allergies are more common in children than adults. Many children will outgrow allergies. Allergies to milk, egg, and soy are most likely to go away over time. However, people who are sensitive to seafood or nuts often have to avoid those foods forever.

Treatment Choices

Allergies can be managed by avoiding foods that cause problems. This can be a challenge with some food groups. Food labels will need to be read carefully. Care will need to be taken when ordering food from staff at restaurants.

Medicine may be needed for more severe allergic reactions. For example, an epinephrine injector (epi pen) may need to be kept nearby at all times. It can give the person medicine to stop or ease severe reactions. Medical care may also be needed after use of the pen.

Sublingual immunotherapy is a newer form of allergy treatment. A small sample of the allergen is placed under the tongue. This process is repeated in a doctor's office over months or years. It may decrease or eliminate response. This treatment is not available for all types of allergens.

Limiting food groups can make it hard to get good nutrition. A doctor or dietitian can help a person get the most out of the foods that can be eaten.


Allergy & Asthma Network
American Academy of Allergy, Asthma & Immunology


Allergy Asthma Information Association


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Last reviewed March 2020 by EBSCO Medical Review BoardDianne Scheinberg Rishikof MS, RD, LDN
Last Updated: 3/3/2021

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