Antihistamines are drugs used to relieve the symptoms of allergies caused by histamine, an amino acid derivative found throughout the body. Histamine was first recognized and suggested as the cause of allergic reactions by Henry Dale (1875-1968) and Patrick Playfair Laidlaw (1881-1940) in 1910. By 1932 histamines were confirmed as causative agents in allergic response. Researchers then sought to find agents that could counteract the effects of histamines.

A Swiss-Italian pharmacologist, Daniele Bovet, of the Pasteur Institute in Paris, France, focused on this problem in 1936. Since histamine is extremely toxic except when introduced to the body by absorption through the intestine, Bovet reasoned that histamine must normally exist in the body in combination with a neutralizing substance. Only "free" histamine would produce allergic symptoms, so an antagonist (an substance that opposes or resists the action of another substance) to this free histamine had to be found. However, histamine has no...