Histamine is an organic nitrogenous compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine is involved in the inflammatory response and has a central role as a mediator of pruritus.ost histamine in the body is generated in granules in mast cells and in white blood cells called basophils and eosinophils. Mast cells are especially numerous at sites of potential injury — the nose, mouth, and feet, internal body surfaces, and blood vessels.