Allergic reaction

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Allergic reaction

An allergic reaction is an overreaction of the immune system to a substance called an allergen. Allergens include chemicals, foods, medicines, mold, plants, and pollen.

Symptoms of an allergic reaction can range from mild and annoying to severe and life-threatening.

Allergens can affect different tissues in the body, such as the airways, eyes, gastrointestinal tract, nose, lungs, and skin.
Some allergic reactions, such as hives or itching around an insect bite or where a plant or chemical touched the skin, affect only one area of the body.
Other allergic reactions may affect the whole body, causing itching, swelling, or difficulty breathing.
A severe allergic reaction (called anaphylaxis) can lead to shock and even death.

Allergic reactions do not occur the first time a person is exposed to an allergen. A person may become more sensitive to the allergen with each exposure.

Credits

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Author	Sydney Youngerman-Cole, RN, BSN, RNC
Editor	Susan Van Houten, RN, BSN, MBA
Associate Editor	Tracy Landauer
Primary Medical Reviewer	William M. Green, MD - Emergency Medicine
Specialist Medical Reviewer	H. Michael O'Connor, MD - Emergency Medicine
Last Updated	July 11, 2007

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Last updated:	July 11, 2007
Author:	Sydney Youngerman-Cole, RN, BSN, RNC
Reviewed By:	William M. Green, MD - Emergency Medicine, H. Michael O'Connor, MD - Emergency Medicine
Editors:	Susan Van Houten, RN, BSN, MBA, Tracy Landauer

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