Histamine

Histamine is a biogenic amine involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by basophils and by mast cells found in nearby connective tissues. Histamine dilates blood vessels and makes the vessel walls abnormally permeable, in order to allow white blood cells and other proteins to engage foreign invaders in the affected tissues.

As an integral part of the immune system, histamine plays a major role in many allergic reactions.