H1 histamine antagonist

H1 histamine antagonists have been used for more than fifty years in allergy medicine and act on histamine H1 receptors. These receptors are located on bronchial cells, some blood vessel cells, and in the intestine. They are used for allergic skin reactions such as urticaria or for allergic rhinitis, hay fever, or allergic conjunctivitis.

How do H1 histamine antagonists work?

The H1 histamine antagonists are administered orally or by injection. They block the H1 receptors for histamine, an important mediator in the allergic reaction. They are both preventative and curative although they can be ineffective in severe allergic reactions.

Do they have side effects?

The H1 histamine antagonists can occasionally cause severe drowsiness in some patients. They can also produce other problems such as dry mouth, constipation, raised intra-ocular pressure, and urinary retention.

Sources:

• Merck Manual – 4^th edition ;
• Principles of internal medicine, TR Harrison, ed. Flammarion.