Diphenhydramine hydrochloride (icon; abbreviated DPH, sometimes DHM) is a first-generation antihistamine

Antihistamine

An H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...

 possessing anticholinergic

Anticholinergic

An anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. An example of an anticholinergic is dicycloverine, and the classic example is atropine....

, antitussive, antiemetic

Antiemetic

An antiemetic is a drug that is effective against vomiting and nausea. Antiemetics are typically used to treat motion sickness and the side effects of opioid analgesics, general anaesthetics, and chemotherapy directed against cancer....

, and sedative

Sedative

A sedative or tranquilizer is a substance that induces sedation by reducing irritability or excitement....

 properties which is mainly used to treat allergies. Like most other first-generation antihistamines, the drug also has a powerful hypnotic

Hypnotic

Hypnotic drugs are a class of psychoactives whose primary function is to induce sleep and to be used in the treatment of insomnia and in surgical anesthesia...

 effect, and for this reason is often used as a non-prescription sleep aid. It is produced and marketed under the trade name Benadryl

Benadryl

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...

 by McNeil-PPC

McNeil Laboratories

McNeil Consumer Healthcare is a medicals products company belonging to the Johnson & Johnson healthcare products group.-History:The company was founded on March 16, 1879 by 23-year-old Robert McNeil, who paid $167 for a drugstore complete with fixtures, inventory and soda fountain, as a retail...

 (a division of Johnson & Johnson

Johnson & Johnson

Johnson & Johnson is an American multinational pharmaceutical, medical devices and consumer packaged goods manufacturer founded in 1886. Its common stock is a component of the Dow Jones Industrial Average and the company is listed among the Fortune 500....

) in the U.S., Canada and South Africa (other trade names in other countries: Dimedrol, Daedalon).