Definition:
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
