What Are Allergies?
Allergies are abnormal immune system reactions to things that are typically harmless to most people. When a person is allergic to something, the immune system mistakenly believes that this substance
is harming the body. Substances that cause allergic reactions — such as some foods, dust, plant pollen, or medicines — are known as allergens. Allergies are a major cause of illness in the United States. Up to 50 million Americans, including millions of kids, have some type of allergy. In fact, allergies cause about 2 million missed school days each year.