A histamine antagonist is an agent which serves to inhibit the release or action of histamine. Antihistamine can be used to describe any histamine antagonist, but it's usually reserved for the classical antihistamines that act upon the H1 histamine receptor. Clinical: H1- and H2-receptor antagonists H1-receptor antagonists In common use, the term antihistamine refers only to H1 antagonists, also known as H1 antihistamines. It has been discovered that these H1-antihistamines are actually inverse… (More on Anti-histamine)