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Causes
Food Allergies are caused by the same basic mechanism as other allergies; they result from an overreaction of the body's immune system to a normally harmless substance. Under usual circumstances, the body deploys the immune system to fight off foreign invaders like parasites, bacteria, or viruses. Allergic reactions occur when the immune system misidentifies harmless foreign substances and reacts to them as if they posed a threat. These substances are called allergens. The allergens that cause the majority of allergic reactions are plant pollens, mold spores, house dust mites, cockroaches, and animal dander (flakes of skin and other debris shed by an animal). Allergic reactions to foods, insect venom, medications, and latex occur less frequently but are not uncommon and tend to be more severe.
Irritants like tobacco smoke, perfumes, or strong cleaning products can make allergy symptoms worse and trigger asthma but are not allergens.
With the first exposures to an allergen, there are no symptoms, but in people who are genetically predisposed to become allergic, the immune system produces an antibody directed against the allergen called IgE. Once produced, IgE attaches to a receptor on the surface of a specialized cell in the body called a mast cell. The next time the body is exposed to the allergen, the IgE antibody tells these specialized cells to release chemicals, including histamine, which cause the symptoms of the allergic reaction.
Asthma and allergies have both been on the rise for several decades, especially in developed countries. One possible explanation for this, called the"hygiene hypothesis,"proposes that children in these countries are exposed to fewer infectious organisms than in the past. As a result, their developing immune systems lack the degree of stimulation by certain bacteria and bacterial products needed for appropriate maturation--and they thus overreact to allergens.
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