antihistamine

Etymology

anti- + histamine

noun

1. (pharmacology) A drug or substance that counteracts the effects of a histamine. Commonly used to alleviate the symptoms of hay fever and other allergies.
   Perhaps the most striking method of demonstrating the effect of antihistamine substances is to use them to protect guinea-pigs against the action of histamine sprayed into the air from an atomizer. December 1946, British journal of pharmacology and chemotherapy, volume 1, number 4, page 278