Description an ethanolamine-derivative, first generation histamine h1 antagonist used in hay fever, rhinitis, allergic skin conditions, and pruritus.indication for the relief of symptoms associated with allergic rhinitis such as sneezing, rhinorrhea, pruritus and acrimation. also for the management of mild, uncomplicated allergic skin manifestations of urticaria and angioedema. used as self-medication for temporary relief of symptoms associated with the common cold.mechanism of action clemastine is a selective histamine h1 antagonist and binds to the histamine h1 receptor. this blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms brought on by histamine.