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Updated February 08, 2008


Histamine is a protein released by mast cells in the immune system when the body encounters an allergen. The release of histamine causes inflammation and is responsible for a number of allergic symptoms, including asthma, swelling, and rhinitis.

Many over-the-counter and prescription allergy drugs are antihistamines, which work by blocking the action of histamine in the body.

Pronunciation: HISS-ta-mean

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