A food allergy is a condition that causes your immune system to treat a normally harmless type of food as if was a dangerous virus, bacteria, or other infectious agent. The immune system response to a food allergy ranges from mild rashes to abdominal pain to a life-threatening complication called anaphylactic shock. Food allergies are more common in children than adults, affecting about 5 percent of children in the United States. Many children outgrow their allergies as they get older. Almost 90 percent of all food allergies are caused by the following foods: - Milk - Soy - Wheat - Eggs - Tree nuts (including almonds, walnuts, pecans, and cashews) - Fish - Shellfish - Peanuts For some people, even the tiniest amount of the allergy-causing food can trigger life-threatening symptoms. Of the foods listed above, peanuts, tree nuts, shellfish, and fish usually cause the most serious allergic reactions. Food allergy testing can find out whether you or your child has a food allergy. If a food allergy is suspected, your primary care provider or your child's provider will probably refer you to an allergist. An allergist is a doctor who specializes in diagnosing and treating allergies and asthma.