Allergic Reactions

Food normally doesn't provoke a response from the human immune system, the body's defense against microbes and other threats to health. In food allergies, two parts of the immune response are involved, according to researchers at the National Institute of Allergy and Infectious Diseases. One is the production of an antibody called immunoglobulin E (IgE) that circulates in the blood. The other part is a type of cell called a mast cell. Mast cells occur in all body tissues but especially in areas that are typical sites of allergic reactions, including the nose, throat, lungs, skin, and gastrointestinal tract.

People usually inherit the ability to form IgE against food. Those more likely to develop food allergies come from families in which allergies such as hay fever, asthma, or eczema are common.

A predisposed person must first be exposed to a specific food before IgE is formed. As this food is digested for the first time, tiny protein fragments prompt certain cells to produce specific IgE against that food. The IgE then attaches to the surface of mast cells. The next time the particular food is eaten, the protein interacts with the specific IgE on the mast cells and triggers the release of chemicals such as histamine that produce the symptoms of an allergic reaction.

If the mast cells release chemicals in the nose and throat, the allergic person may experience an itching tongue or mouth and may have trouble breathing or swallowing. If mast cells in the gastrointestinal tract are involved, the person may have diarrhea or abdominal pain. Skin mast cells can produce hives or intense itching.

The food protein fragments responsible for an allergic reaction are not broken down by cooking or by stomach acids or enzymes that digest food. These proteins can cross the gastrointestinal lining, travel through the bloodstream and cause allergic reactions through out the body.

The timing and location of an allergic reaction to food is affected by digestion. For example, an allergic person may first experience a severe itching of the tongue or "tingling lips." Vomiting, cramps or diarrhea may follow. Later, as allergens enter the bloodstream and travel through out the body, they can cause a drop in blood pressure, hives or eczema, or asthma when they reach the lungs. The onset of these symptoms may vary from a few minutes to an hour or two after the food is eaten.

Allergic Reasction from foods can be dangerous!