An allergy is a chronic condition involving an abnormal reaction to an ordinarily harmless substance called an allergen.

If you have an allergy, your immune system views the allergen as an invader and a chain reaction is initiated. White blood cells of the immune system produce IgE antibodies. These antibodies attach themselves to special cells called mast cells, causing a release of potent chemicals such as histamine. These chemicals cause symptoms such as:

• Itching in the nose, roof of the mouth, throat, eyes
• Sneezing 
• Stuffy nose (congestion) 
• Runny nose 
• Tearing eyes 
• Dark circles under the eyes

Learn more about allergy symptoms, diagnosis, treatment and management.

Courtesy of the The American Academy of Allergy Asthma and Immunology (AAAAI)

Reprinted from with permission of the American Academy of Otolaryngology—Head and Neck Surgery, copyright © 2016. All rights reserved