Article Outline
Food Allergy and Intolerance, conditions that result in a variety of adverse physiological reactions caused by eating specific foods. True food allergy involves an immune response, while food intolerance does not.
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Symptoms of Food Allergy
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Food allergies are most frequently caused by eggs, milk, peanuts, shellfish, soy, tree nuts, and wheat. Symptoms generally appear from within minutes to two hours after the food has been ingested. In cases of allergic rhinitis, symptoms may appear many hours or even days after the food allergen has been ingested. Symptoms of food allergy include swelling of the tongue or throat, difficulty breathing, abdominal cramps, vomiting, diarrhea, and even loss of consciousness. In a small percentage of individuals, food allergy causes a life-threatening reaction called anaphylaxis. A slight tingling on the tongue or in the mouth after eating apples or stone fruit often accompanies hay fever. A patient may have eaten the food allergen on a daily basis for years without realizing any connection to symptoms.
Food allergies can affect almost any part of the body and give rise to diseases such as eczema, asthma, and urticaria (hives). In some patients physical exercise can trigger an allergic reaction, a condition called exercise-induced urticaria.
Food allergies are caused by an immune response. When the immune system identifies a substance as harmful, it produces the antibody immunoglobulin E (IgE). This triggers an “explosion” of histamine from mast cells, which are found in the mouth, nose, gut, and skin. The release of histamines can cause itching, sneezing, wheezing, rash, and diarrhea. Antihistamines combat the symptoms to some extent.
Doctors diagnose food allergies by testing the skin or the blood. Skin testing is a safe, simple procedure. It involves pricking or injecting the surface of the skin with a small amount of potential allergen. If redness or swelling occurs after about 20 minutes, an allergy is present. Individuals with severe allergies or skin conditions should avoid skin testing. The blood test measures specific IgE levels. It is not always as accurate as skin testing because some food allergy patients do not have detectable levels of IgE in the blood. According to the Asthma and Allergy Foundation of America, between 1 and 2 percent of adults suffer from true food allergy.
While food allergy involves an immune response, food intolerance does not. Studies show that food intolerance is involved in conditions such as irritable bowel syndrome (IBS), migraine, arthritis, Crohn’s disease, and hyperactivity. Lactose intolerance is one of the most common instances of food intolerance. Symptoms of food intolerance include headache, abdominal cramps, bloating, flatulence, and diarrhea.
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