What does an allergy mean?

allergy information

Medical Editor: William C. Shiel Jr., MD, FACP, FACR

An allergy refers to an exaggerated reaction by our immune system in response to bodily
contact with certain foreign substances. It is exaggerated because these foreign substances are usually seen by the body as harmless and no response occurs in non- allergic people. Allergic people's bodies recognize the foreign substance and one part of the immune system is turned on. Allergy-producing substances are called "allergens." Examples of allergens include pollens, dust mite, molds, danders, and foods. To understand the language of allergy it is important to remember that allergens are substances that are foreign to the body and can cause an allergic reaction in certain people.

When an allergen comes in contact with the body, it causes the immune system to develop an allergic reaction in persons who are allergic to it. When you inappropriately react to allergens that are normally harmless to other people, you are having an allergic reaction and can be referred to as allergic or atopic. Therefore, people who are prone to allergies are said to be allergic or "atopic."

Austrian pediatrician Clemens Pirquet (1874-1929) first used the term allergy. He referred to both immunity that was beneficial and to the harmful hypersensitivity as "allergy." The word allergy is derived from the Greek words "allos," meaning different or changed and "ergos," meaning work or action. Allergy roughly refers to an "altered reaction." The word allergy was first used in 1905 to describe the adverse reactions of children who were given repeated shots of horse serum to fight infection. The following year, the term allergy was proposed to explain this unexpected "changed reactivity."

Allergy Fact

• It is estimated that 50 million North Americans are affected by allergic conditions.
• The cost of allergies in the United States is more than $10 billion dollars yearly.
• Allergic rhinitis (nasal allergies) affects about 35 million Americans, 6 million of whom are children.
• Asthma affects 15 million Americans, 5 million of whom are children.
• The number of cases of asthma has doubled over the last 20 years.