Allergies are abnormal reactions of the immune
system which occur in response to otherwise harmless
substances.
Allergies are among the most common of medical disorders. It
is estimated that 60 million Americans, or more than one in every five people,
suffer from some form of allergy, with similar proportions throughout much of
the rest of the world. Allergy is the single largest reason for school absence
and is a major source of lost productivity in the workplace.
An allergy
is a type of immune reaction. Normally, the immune system responds to foreign
microorganisms or particles, like pollen or dust, by producing specific
proteins called antibodies that are capable of binding to identifying
molecules, or antigens, on the foreign particle. This reaction between antibody
and antigen sets off a series of reactions designed to protect the body from
infection. Sometimes, this same series of reactions is triggered by harmless,
everyday substances. This is the condition known as allergy, and the offending
substance is called an allergen.
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