WordNet records no synonym and no antonym for histamine. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
amine formed from histidine that stimulates gastric secretions and dilates blood vessels; released by the human immune system during allergic reactions
Synonyms, antonyms and the broader and narrower relations for histamine come from Princeton University’s WordNet. Full sources and licences.