Food allergy

Food allergy is an immune system reaction that occurs soon after eating a certain food. Even a tiny amount of the allergy-causing food can trigger signs and symptoms such as digestive problems, hives or swollen airways. In some people, a food allergy can cause severe symptoms or even a life-threatening reaction known as anaphylaxis.

Food allergy affects an estimated 6 to 8 percent of children under age 3 and up to 3 percent of adults. While there's no cure, some children outgrow their food allergy as they get older.

It's easy to confuse a food allergy with a much more common reaction known as food intolerance. While bothersome, food intolerance is a less serious condition that does not involve the immune system.

Symptoms Causes Risk factors Complications Prevention

For some people, an allergic reaction to a particular food may be uncomfortable but not severe. For other people, an allergic food reaction can be frightening and even life-threatening. Food allergy symptoms usually develop within a few minutes to two hours after eating the offending food.

The most common food allergy signs and symptoms include:

  • Tingling or itching in the mouth
  • Hives, itching or eczema
  • Swelling of the lips, face, tongue and throat or other parts of the body
  • Wheezing, nasal congestion or trouble breathing
  • Abdominal pain, diarrhea, nausea or vomiting
  • Dizziness, lightheadedness or fainting


In some people, a food allergy can trigger a severe allergic reaction called anaphylaxis. This can cause life-threatening signs and symptoms, including:

  • Constriction and tightening of airways
  • A swollen throat or the sensation of a lump in your throat that makes it difficult to breathe
  • Shock with a severe drop in blood pressure
  • Rapid pulse
  • Dizziness, lightheadedness or loss of consciousness

Emergency treatment is critical for anaphylaxis. Untreated, anaphylaxis can cause a coma or even death.

Exercise-induced food allergy

Some people have an allergic reaction to a food triggered by exercise. Eating certain foods may cause you to feel itchy and lightheaded soon after you start exercising. In serious cases, an exercise-induced food allergy can cause certain reactions such as hives or anaphylaxis.

Not eating for a couple of hours before exercising and avoiding certain foods may help prevent this problem.

Pollen-food allergy syndrome

In many people who have hay fever, fresh fruits and vegetables and certain nuts and spices can trigger an allergic reaction that causes the mouth to tingle or itch. In some people, pollen-food allergy syndrome — sometimes called oral allergy syndrome — can cause swelling of the throat or even anaphylaxis.

This is an example of cross-reactivity. Proteins in fruits and vegetables cause the reaction because they're similar to those allergy-causing proteins found in certain pollens. For example, if you're allergic to ragweed, you may also react to melons; if you're allergic to birch pollen, you may also react to apples.

Cooking fruits and vegetables can help you avoid this reaction. Most cooked fruits and vegetables generally don't cause cross-reactive oral allergy symptoms.

Common cross-reactivity between pollens and fruits and vegetables:

If you are allergic to:Birch pollenRagweed pollenGrassesMugwort pollen
You may also have a reaction to:Apples
Raw potatoes
(cantaloupe, honeydew and watermelon)
(cantaloupe, honeydew and watermelon)
White potato
Bell pepper
Some spices (caraway seeds, parsley, coriander, anise seeds, fennel seeds)

When to see a doctor

See a doctor or allergist if you have food allergy symptoms shortly after eating. If possible, see your doctor when the allergic reaction is occurring. This will help your doctor make a diagnosis.

Seek emergency treatment if you develop any signs or symptoms of anaphylaxis, such as:

  • Constriction of airways that makes it difficult to breathe
  • Shock with a severe drop in blood pressure
  • Rapid pulse
  • Dizziness or lightheadedness

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