Food allergies are abnormal responses to foods. They’re triggered by the body’s immune (infection-fighting) system. They may be chronic (last a long time) or acute (sudden). Acute reactions can cause serious illness or even life-threatening reactions called anaphylaxis.
Food allergies are most common in children, especially babies and toddlers. Food allergies occur in 6% to 8% of young children and about 4% of adults. Children may outgrow allergies to milk, soy, wheat, and eggs.
The immune system mistakenly sees a food as harmful (an allergen). Cells make immunoglobulin E (IgE) antibodies to fight the food. Even a tiny amount of the food can trigger symptoms. Foods accounting for 90% of all such reactions are milk, eggs, peanuts, tree nuts (walnuts, cashews), fish, shellfish (shrimp, lobster, crab), soy, and wheat. Adults usually have reactions to fish, shellfish, peanuts, tree nuts, fruits, and eggs. Children react to eggs, milk, peanuts, and tree nuts. Tree nuts and peanuts are leading causes of anaphylaxis.
Symptoms usually start minutes to 2 hours after food is eaten. Symptoms include tingling in the mouth and swelling of lips, face, tongue, and throat. Others are wheezing, nasal congestion, hives, itching, and eczema. People can have nausea, vomiting, cramps or pain in the abdomen (belly), diarrhea, or low blood pressure. Severe reactions include trouble breathing, dizziness, lightheadedness, fainting, chest or throat tightness, rapid or abnormal heartbeat, losing consciousness, and even death.
The medical (and family) history is most important for diagnosis. The health care provider also uses food diaries, elimination diets, skin tests, blood tests, and food challenges. In elimination diets, possible problem foods are avoided for a week or two and then are added back into the diet one at a time.
Avoiding problem foods is most important, as is learning how to do this. Reading ingredient labels for all foods is critical.
Over-the-counter antihistamines can help minor reactions.
Doctors sometimes prescribe antihistamines and steroids. Severe reactions may need emergency epinephrine and a trip to the hospital. Many people carry an autoinjector (EpiPen, Twinject) that contains epinephrine.
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