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A food allergy is an immunologic response to a food protein. It is estimated that up to 12 million Americans have food allergies of one type or another, and the prevalence is rising. Six to eight percent of children have food allergies and two percent of adults have them. The most common food allergies in adults are shellfish, peanuts, tree nuts, sesame seeds, fish, and eggs, and the most common food allergies present in children are milk, eggs, and peanuts.

The place to start when talking about allergies is with the immune system. The immune system is the catch-all term for the various bodily systems that act to fight against disease and toxins. These include the white blood cells, or leukocytes; the skin and mucous membranes that act as physical barriers to germs; and the bone marrow and spleen that produce disease fighting cells called antibodies. When the body is exposed to germs, the immune system produces antibodies to the specific germs (or antigens) it was exposed to in order to fight them off in the future. These antibodies bind to antigens to attack them.

How the Immune System Works in a Food Allergy:

For the most part, this system works well. The body recognizes cells that are part of itself and cells that are not, and recognizes cells that are threatening (e.g., viruses and bacteria) and cells that are harmless (e.g., food and pollen). However, in allergic individuals, the immune system identifes a food as a germ or antigen and produces antibodies --- specifically, Immunoglobulin IgE --- to it. A food that has been primed in this manner is called an allergen. The resulting IgE/mast cell complex recognizes and binds to allergens, and this reaction stimulates the release of histamine and other chemicals.

Allergic Reactions:

When the body is exposed to an allergen, Immunoglobulin IgE attaches to what it perceives as a foreign invader and releases a number of chemicals as a form of attack. The most well-known chemical, which is responsible for a host of allergic symptoms, released in this reaction is called histamine. (Many drugs that treat allergies are called antihistamines because they treat the effects of this chemical). Histamine induces tissue swelling and can cause a host of local and systemic symptoms, including hives, rhinitis, and vomiting.

Basic Treatment:

The basic treatment for food allergies is strict avoidance of the allergen. Unlike environmental allergens, which can sometimes be effectively treated by daily courses of antihistamines or by taking allergy shots, abstinence from allergens is currently the only medically accepted treatment for food allergies.

Emergency Treatment:

Allergic emergencies occur when a patient experiences a severe asthma attack or anaphylactic shock. Both of these events require prompt emergency attention. Patients or bystanders should call emergency medical services if an allergic individual has severe difficulty breathing, suddenly experiences a loss of consciousness, or experiences other symptoms that lead them to believe they are in the initial stages of an allergic reaction. If they have been prescribed rescue medication (such as epinephrine), they should take it per their doctor's instructions.