Pronunciation: (his'tu-mēn", -min),[key] —n. 1. Physiol.a histidine-derived amine compound that is released mainly by damaged mast cells in allergic reactions, causing dilation and permeability of blood vessels and lowering blood pressure.
2. Pharm.a commercial form of this compound, obtained from histidine and used chiefly in the diagnosis of gastric and circulatory functions. Cf. antihistamine.Also,his•ta•minPronunciation: (his'tu-min).[key]