Specificity and Mode of Action of Histamine

Abstract

WHEN human skin is injured, a substance is released into the tissue spaces which brings about the so-called triple response: a local dilatation of the skin vessels, an increase in their permeability leading to wheal formation, and around this an area of further vasodilatation without notable change in permeability, mediated through a nerve axon reflex. Lewis has shown¹ that when a needle is pricked into the skin through a drop of a dilute solution of a histamine salt, this same triple response occurs, and he therefore suggests that the natural excitant substance (H-substance) may also be histamine. We have investigated the chemical specificity of the response in detail by Lewis's simple technique, comparing all results with the negligible effects of control pricks through 0·9 per cent saline.