Definition: A foreign substance which causes the immune system to produce immunoglobulin E antibody (IgE) against the substance. The IgE binds to cells such as mast cells and basophils. Upon re-exposure, the same foreign substance binds to IgE, causing chemical mediators to be released from the mast cells and basophils, resulting in vasodilation, itching, sneezing, wheezing and other allergic symptoms.
Allergy
By Daniel More, MD, About.com
Created: December 11, 2006
About.com Health's Disease and Condition content is reviewed by our Medical Review Board
Explore Allergies
Must Reads
About.com Special Features
Do I Have Allergies?
Are your symptoms merely irritating, or could they be a sign of allergies? More >
Preventing Headaches
The best way to treat a headache is to prevent it. Learn how. More >
Also from About.com:
©2009 About.com, a part of The New York Times Company.
All rights reserved.