Since an important mediator of allergies is a chemical produced by certain cells inside the body—histamine—we can administer antihistamines. But they are rarely fully effective, and some have annoying side effects, like making a patient sleepy. Sometimes we use steroids or other agents which stabilize the cells that release histamine and other annoying products so as to decrease the release of materials causing symptoms. Histamine is not the only material that causes allergic symptoms, so we also try to block the activities of some other chemicals after exposure to an allergen.