Histamine is a biogenic amine involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. (Wikipedia)
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These substance are chemically known as beta-imidazolylethylamine which are released by the body in response to various allergens. You can also get it in medicated form. [What you get medically are...
It's an Amine formed from histidine that stimulates gastric secretions and dilates blood vessels; released by the humane immune system during allergic reactions
Histamine is an autocoid ( local harmone) produced from the amino acid histidine, that is usually present in the human body. It exerts a pharmacologic action when released from injured cells....