Definition: An allergen is a substance that causes the immune system to react abnormally. Some people are sensitive to certain allergens, such as grass, pollen, dust and pet dander. In sensitive people, allergens can cause mast cells in their eyes to release histamines, resulting in eye allergy symptoms such as redness, itching and tearing.
Allergen
By Troy Bedinghaus, O.D., About.com Guide
Created: September 09, 2009
About.com Health's Disease and Condition content is reviewed by the Medical Review Board
Suggested Reading
Explore Vision
Must Reads
About.com Special Features
8 Ways to Cut Drug Costs
Learn how to save money on medications with these recommendations. More >
Healthy Bodies, Healthy Minds
Keep yourself, and your family, happy and healthy this season. More >
Also from About.com:
©2009 About.com, a part of The New York Times Company.
All rights reserved.