Food Allergy Basics

If your immune system is activated by a particular food protein you eat, you have a food allergy. As many as 12 million people in the United States have such allergies, including about seven percent of children and less than five percent of adults.

To understand why some people develop food allergies, it is important to first understand how the immune system in your body works. Normally, our immune system reacts to dangerous external elements by producing a group of cells known as Immunoglobulin E (IgE) antibodies. These antibodies act to guard our body against bacteria and viruses that can cause infections and other illnesses. 

A food allergy occurs due to an immune system malfunction. The immune system comes into contact with certain proteins in a food and then marks that protein as dangerous, even though it’s not. This sensitization triggers an inflammatory response sparked by the release of IgE antibodies and eosinophils (white blood cells produced in the blood marrow) and other cell types. The next time your immune system is exposed to that food protein, the IgE antibodies recognize them as “dangerous,” signaling your immune system to release histamines and other chemicals into your body. This causes the symptoms of an allergic reaction.

Eight kinds of food cause 90 percent of food allergies:

• Milk
• Eggs
• Peanuts
• Wheat
• Soy
• Fish
• Shellfish (shrimp, lobster, crab)
• Tree nuts (almonds, pecans, walnuts)

For some people, allergic reactions to food are mild; uncomfortable but not dangerous. Occasionally, however, an allergic reaction can produce more severe and even dangerous reactions. In the most severe cases, a food allergy can result in anaphylactic shock, which is an emergency situation where breathing becomes difficult and blood pressure drops dangerously.