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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
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
Anaphylaxis
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 the 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.
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
Causes
When you have a food allergy, your immune system mistakenly identifies a specific food or a substance in food as something harmful. In response, your immune system triggers cells to release an antibody known as immunoglobulin E (IgE) to neutralize the allergy-causing food or food substance (the allergen).
The next time you eat even the smallest amount of that food, IgE antibodies sense it and signal your immune system to release a chemical called histamine, as well as other chemicals, into your bloodstream. These chemicals cause allergy symptoms.
In adults, the majority of food allergies are triggered by certain proteins in:
- • Shellfish, such as shrimp, lobster and crab
- • Peanuts
- • Tree nuts, such as walnuts and pecans
- • Fish
In children, food allergies are commonly triggered by proteins in:
- • Peanuts
- • Tree nuts
- • Eggs
- • Cow's milk
- • Wheat
- • Soy
Pollen-food allergy syndrome
Also known as oral allergy syndrome, pollen-food allergy syndrome affects many people who have hay fever. In this condition, certain fresh fruits and vegetables or nuts and spices can trigger an allergic reaction that causes the mouth to tingle or itch. In serious cases, the reaction results in swelling of the throat or even anaphylaxis.
Proteins in certain fruits, vegetables, nuts and spices cause the reaction because they're similar to allergy-causing proteins found in certain pollens. This is an example of cross-reactivity.
When you cook foods that trigger pollen-food allergy syndrome, your symptoms may be less severe.
This following table shows the specific fruits, vegetables, nuts and spices that can cause pollen-food allergy syndrome in people who are allergic to different pollens.