What are antihistamines?

Antihistamines

These drugs are also called as anti – allergic drugs and are used to treat allergy, e.g, skin rashes. Since the allergic reactions are caused due to liberation of histamine in the body that is why these drugs are called antihistamines. Other than skin rashes these drugs are useful for conjunctivitis and rhinitis. In seasonal rhinitis and conjunctivitis, these drugs relieve sneezing, nasal discharge and itching of eyes, nose and throat, e.g diphenylhydramine, promethazine and terfenadine. They interfere with the natural action of histamine by competing with histamine for binding sites of receptor.