Benadryl is a brand name allergy medicine marketed over-the-counter by Johnson & Johnson subsidiary McNeil Consumer Healthcare. Prior to 2007, Benadryl was marketed by Pfizer Consumer Healthcare. Benadryl is used as an antihistamine for the temporary relief of seasonal and perennial allergy symptoms. It will also help with normal symptoms of insect stings even if there is no allergic reaction. Benadryl is available for oral or topical use.
In the United States and Canada, Benadryl products contain the first-generation antihistamine diphenhydramine. Diphenhydramine is used as an allergy treatment in various forms around the world. Diphenhydramine is an H-1 receptor antagonist. Antagonism is achieved through blocking the effect of histamine more than blocking its production or release. Diphenhydramine inhibits most responses of smooth muscle to histamine and acts as a vasoconstrictor by inhibiting the vasodilator effects of histamine. The antagonism may also produce anticholinergic effects, antiemetic effects, and significant sedative side effects.
In the United Kingdom, Benadryl products contain either the second-generation non-sedating antihistamine acrivastine (marketed as Benadryl Allergy Relief, with a suggested efficacy duration of eight hours) or the non-sedating antihistamine cetirizine (marketed as Benadryl One a Day Relief). Cetirizine is indicated for the relief of symptoms associated with allergy and hives. Cetirizine is an orally active and selective H1-receptor antagonist.
Benadryl products are marketed in Australia and New Zealand by Johnson & Johnson Pacific.