Food Allergies

A food allergy is an exaggerated, adverse immune reaction to food affecting 6 to 8 percent of children under 3 to 6 years old and 3 to 4 percent of adults, and the incidence is rising. A food allergy is different from the more common food intolerance. There are nine common food allergies and several lesser ones. Most allergies are IgE mediated, involve histamine release, and can be diagnosed by one of several tests. The only treatment is strict avoidance.

A food allergy is a type I immediate hypersensitive reaction mediated by the immune system involving an antibody immunoglobulin, IgE, and mast cells. When the individual is first exposed to the food, his or her white blood cell lymphocytes produce the IgE antibody to the food allergen, a protein in the food. Upon reexposure, the IgE antibody on the mast cell prompts the release of histamine. This can occur anywhere from within seconds to after two hours. The location of the tissue from which the histamine is released and to which it is carried determines the symptoms that an individual develops.

The classic IgE-mediated reaction occurs from oral exposure and can produce oral symptoms. Second, the IgE and/or non-IgE-mediated reaction can produce esophagitis, gastritis, and gastroenteritis. Third, the non-IgE-mediated response can produce protein-induced enterocolitis syndrome; food-protein proctocolitis or proctitis; protein-induced enteropathy (e.g., Celiac disease); milk-soy protein intolerance (especially during infancy [Page 168]or childhood); and Heiner syndrome, a serious lung disease due to milk-protein IgG antibody-immune complexes. The classic type I mediated IgE response can include angioedema, with swelling of the eyelids, face, lips, tongue, and voice box. The patient may also develop hives and itching of the mouth, throat, eyes, and skin. Nausea, vomiting, diarrhea, and abdominal cramping pain can also occur. Nasal congestion is possible, as is wheezing, a scratchy throat, shortness of breath, and difficulty swallowing. Anaphylaxis is a severe systemic reaction leading to a sudden drop in blood pressure and edema, causing bronchoconstriction that can be fatal within minutes. This is why avoidance of the offending food is essential.