Food allergies are defined as toxic clinical reactions to food or food additives that involve the immune system. The immune system is a complex system whose cells and molecules are found throughout your body to protect it from potentially harmful foreign molecules. It is most active in the areas of the body which have some direct contact with the outside world such as the skin, lungs, nose and gastrointestinal tract. The majority of potentially harmful molecules enter your body through your intestinal tract therefore, it is not surprising that over 60% of immune activity occurs in this area. The immune system is made up of a team of different types of cells that, while each having their own specific function, work together to protect the body from foreign invaders: B-cells produce antibodies; T-cells conduct surveillance for potentially dangerous molecules and kills dangerous cells such as disease-causing bacteria; and macrophages are the scavenger cells of your body acting like garbage trucks, cleaning up residue and removing potentially dangerous substances.
A surveillance team of cells determines whether newly introduced molecules pose a threat to your system. New molecules are constantly being introduced into the intestinal tract by the food that we eat. An allergic reaction occurs when your body identifies molecules as potentially harmful and toxic; these molecules are called antigens. The surveillance cells bind to the antigens activating the immune cells to release histamine and other chemicals which then signals the scavenger macrophages to come to the site and destroy them. Allergic reactions involving excessive histamine release can cause anaphylactic reactions (difficulty in breathing) which are responsible for 29,000 people in the United States ending up in the emergency ward each year. When the surveillance immune cells bind to an antigen and send out chemical messengers, they also communicate to other immune cells, the B-cells, which are instructed to make antibodies to the antigen
(Figure 1. Immune cell bonds antigen and releases chemical messengers, e.g., histamine)
Antibodies are long, branched molecules that have places for recognition and binding (attachment) of the antigen on one side, and a site on the other end that can call into action other immune responses.
An antibody will only bind one specific antigen and nothing else. When the antibody binds, or sticks, to the dangerous molecule it is acts like a red flag identifying the molecule as something potentially damaging that should be removed. Your macrophage cells are often called the 'scavenger' cells of the immune system and are specifically designed to remove damaging molecules from the body. After the antibody binds to a dangerous molecule the macrophages consume the molecule, taking it out of circulation and destroying it.
(Figure 2. Immune cell binds antigen and is activated to make antibodies. Antibodies bind antigens, and macrophages scavenge the antigen-antibody complexes.)
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