Definition & Meaning of "antihistamine"

What is "antihistamine"?

Antihistamine is a type of medication used to ease allergy symptoms by blocking the action of histamines in the body. Histamines are chemicals released by the immune system during allergic reactions, causing symptoms such as sneezing, itching, runny nose, and watery eyes. Antihistamines work by stopping histamines from attaching to receptors in the cells, and so reducing or preventing these allergic symptoms. They are commonly used to treat hay fever, hives, pink eye caused by allergies, and sometimes symptoms of the common cold.