What is food allergy?
Non-allergic (non-immune) adverse reactions are termed food intolerance (e.g., pharmacological reactions caused by chemical components of foods, or intolerance to the milk protein lactose, caused by a deficiency of lactase, the enzyme which helps to digest the milk protein lactose).
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How does food allergy develop? The gastrointestinal tract (gut) starts at the mouth. Food moves down from the mouth via the oesophagus into the stomach and from there is processed through the small and large intestines, where it is eventually eliminated with defecation. The intestinal tract processes food to extract the nutrients and normally blocks allergens from entering the body. Many of the immunological and mechanical barriers involved in this process are immature at birth, leaving the infant at risk for allergens to enter the blood stream. Large amounts of food allergens penetrate the gut barriers in children and adults, but the body's defense, the immune system, develops a tolerance to the allergens. Thus, no symptoms occur. A failure to develop tolerance or a breakdown in tolerance results in allergen sensitization (excessive production of food-specific IgE antibodies). When food allergens subsequently penetrate the gut lining and reach the food-specific IgE antibodies bound to mast cells, a number of chemicals, including histamine, are released, leading to a variety of symptoms affecting the gut, skin, nose, lungs and/or the heart and circulation. The skin, nose and lungs are most often affected by food-induced allergic reactions involving specific IgE antibodies to a food. Disorders of the gut are mostly due to non-allergic reactions.
How common is food allergy and whom does it affect?
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Food sensitivity can be so severe that a systemic reaction involving the whole body, anaphylaxis, can occur from breathing airborne particles of the food allergen to which the subject is allergic, for example inhaling the odors of cooked or raw fish.
Which foods commonly cause allergy and anaphylaxis?
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