Allergy

Allergy Symptoms

Medical Reviewer: Melissa Conrad Stöppler, MD

Allergies are exaggerated immune responses to environmental triggers known referred to as allergens.

What is an allergy?

An allergy refers to an exaggerated reaction by our immune system in response to exposure to certain foreign substances. It is exaggerated because these foreign substances are usually seen by the body as harmless and no response occurs in nonallergic people. In allergic individuals, the body recognizes the foreign substance and one arm of the immune system generates a response.

Allergy-producing substances are called "allergens." Examples of allergens include pollens, dust mites, molds, animal proteins, foods, and even medications. 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 allergic individual comes in contact with an allergen, the immune system mounts a response through the IgE antibody. 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. Generally speaking, allergy therefore 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."

Reviewed on 11/26/2013

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