In this review you will learn how allergy relates
to the immune system. You will begin understanding how and
why certain people become allergic. The most common allergic
diseases are discussed briefly in this article.
An allergy refers to a misguided reaction by
our immune system in response to bodily contact with certain
 foreign substances. It is misguided because these foreign
substances are usually harmless and remain so to non- allergic
people. 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."
- 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.
- Hay fever 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.
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