Diphenhydramine (/ˌdaɪfɛnˈhaɪdrəmiːn/; abbreviated DPH, sometimes DHM) is a first-generation antihistamine possessing anticholinergic, antitussive, antiemetic, and sedative properties that is mainly used to treat allergies. It is also used in the management of drug-induced parkinsonism and other extrapyramidal symptoms. The drug has a strong hypnotic effect and is FDA-approved as a nonprescription sleep aid, especially in the form of diphenhydramine citrate.