Adverse Food Reactions and Allergies

An adverse food reaction is defined as any untoward reaction following the ingestion of food (Lifshitz 1988). These reactions generally fall into two categories: food intolerance and food hypersensitivity. Intolerances are nonimmunologic (Sampson and Cooke 1990) and are responsible for most adverse food reactions. They may be idiosyncratic, due to metabolic disorders, or caused by pharmacological substances such as toxins or drugs present in food. Food additives can also be a cause of food intolerance or hypersensitivity and can produce respiratory and gastrointestinal complaints (Lifshitz 1988).

True food hypersensitivity, or allergy, is an adverse food reaction involving immunologic mechanisms. It is initiated by production of specific antibodies, otherwise known as immunoglobulins, in reaction to food constituents. The body manufactures antibodies as part of its regular defense system against foreign invaders such as viruses and bacteria. In certain individuals, the immune system is triggered to elicit a specific antibody, called immunoglobulin E (IgE), against various environmental substances like pollens, pet dander, insect venoms, and foods. The common immunologic mechanisms involved can cause food-allergic reactions to resemble allergic reactions to honeybee stings or penicillin.

Mechanism

In food-allergic individuals, IgE antibodies are produced against food components and circulate in the blood. Upon reaching certain cells, known as mast cells and basophils, the IgE becomes fixed to the cell surface and remains there. These cells contain high quantities of special receptors for IgE; rat mast cells have been found to contain 2-5 × 105 receptors per cell (Mendoza and Metzger 1976). A large portion of the IgE in the body is fixed to these cells, and when they become armed with IgE, they are said to be “sensitized.”