If you have an allergy, your body's immune system has been programmed to treat a particular substance in food or the environment as an enemy. Defending us against harmful substances is part of the immune system's job. With allergies, the immune system reacts to a substance that, for the non-allergic person, is completely harmless. Hay fever, for example, is an allergic reaction to pollen. Why do some people have hay fever, while everyone else can breathe in pollen particles with no problem? Because the immune system in the hay fever sufferer sets an allergic reaction in response to pollen molecules that come in contact with sinus passages.

The specific substances that cause allergic reactions are called "allergens." Composed largely of protein, allergens can be food ingredients, chemicals, or environmental substances such as pollen, dust mites, and animal dander. (Another word for allergen is "antigen.")

The allergic reaction, also known as a "hypersensitive" reaction, triggers the release of chemicals into the blood stream, chiefly histamine. Normally stored away inside cells that are part of the immune system, these chemicals produce the various symptoms and discomforts of allergies. These symptoms ranges in severity from mild to life-threatening.

The immune system has two basic functions. First our immune defenses recognize and destroy bacteria, viruses, parasites, and any other foreign invaders. Second, the immune system works to minimize the damage to tissues and organs from the invasion.

The immune system consists of several branches, each with its own protective functions. White blood cells known as "B cells" (B-lymphocytes) play a key role. B cells coordinate with other cells in the blood called "plasma cells" to produce a series of large proteins known as immunoglobulins. Immunoglobulins are antibodies capable of recognizing, destroying, and positioning antigens for removal from the body.

The immune system has five different classes of antibodies: IgE, IgA, IgG, IgM, and IgD. Each class is designed to go after certain category of antigens. Antibodies are "antigen-specific," which is to say that an individual antibody is programmed to recognize and attack a specific foreign invader. For example, antibodies against viruses are assigned to one virus only. When the body becomes infected by a flu virus, a specific antibody is created to recognize and destroy the virus. This is how we become immune to future infections by the same virus.

IgE (immunoglobulin E) is the antibody class that is largely responsible for allergic reactions. IgE triggers a special type of immune cell called the "Mast cell" to release histamine and other potent chemicals into the blood stream. The first line of our immune defense network, Mast cells act like sentries at the places where we interface with the outside world: the intestinal tract, the sinuses, the lungs, and the skin. Mast cells come equipped with IgE antibodies positioned on their surfaces. Before joining forces with Mast cells, IgE antibodies are pre-set to recognize specific antigens. This pre-programming takes place through the activity of T cells and B cells, which are other key players in the immune system.

When an antigen comes in contact with IgE antibodies, an "antigen-antibody" complex is formed. This complex signals the Mast cell to open up storage granules inside the cell that contain histamine and a host of other potent chemicals. This process is called "degranulation." Once in the bloodstream, these substances produce allergic reactions in the skin, the respiratory tract, and the gastrointestinal tract.

Other antibodies such as IgG and IgM are being implicated in food intolerance reactions, causing a whole different set of symptoms, which could include neuropathy, intestinal symptoms, and problems with energy production.(1)

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