ABSTRACT
Histamine was identified in 1911 as a potent vasoactive substance and was subsequently found to have many other physiologic activities. It was not until 60 years after its discovery that histamine’s activities were shown to be mediated through two types of receptors. The allergyrelated effects of histamine are mediated through its Hi receptor and include smooth muscle contraction, increased vascular permeability, and pruritus (1). The H2 receptors are located primarily in parietal cells in the stomach.
