What Is a Food Allergy?

What Is a Food Allergy?
A food allergy is an adverse reaction to a food or food component that involves the body’s immune system. A true allergic reaction to a food involves three primary components: 1) contact with a food allergen (reaction-provoking substance, virtually always a protein); 2) immunoglobulin E (IgE-an antibody in the immune system that reacts with allergens); and 3) mast cells (tissue cells) and basophils (blood cells), which when connected to IgE antibodies release histamine or other substances causing allergic symptoms.
The body’s immune system recognizes an allergen in a food as foreign and produces antibodies to halt the “invasion.” As the battle rages, symptoms appear throughout the body. The most common reaction sites are the mouth (swelling of the lips), digestive tract (stomach cramps, vomiting, diarrhea), skin (hives, rashes, or eczema), and the airways (wheezing or breathing problems).
Allergic reactions to food are rare and can be caused by any food. The most common food allergens, known as the “Big 8,” are fish, shellfish, milk, egg, soy, wheat, peanuts, and tree nuts such as walnuts, cashews, etc. Symptoms of a food allergy are highly individual and usually begin within minutes to a few hours after eating the offending food. People with true, confirmed food allergies must avoid the offending food altogether.
There are numerous misconceptions regarding allergy to food additives, preservatives, and ingredients. Although some additives and preservatives have been shown to trigger asthma or hives in certain people, these reactions are not the same as those reactions observed with food allergies. These reactions do not involve the immune system and therefore are examples of food intolerance or idiosyncrasy rather than food allergy. Most people consume a wide variety of food additives and ingredients daily, with only a very small number having been associated with adverse reactions.
There are also some adverse reactions to foods that involve the body’s metabolism but not the immune system. These reactions are known as food intolerance. Examples of food intolerance are food poisoning or the inability to properly digest certain food components, such as lactose or milk sugar. This latter condition is commonly known as lactose intolerance.


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