Diphenhydramine hydrochloride is one of the common anticholinergic drugs. Anticholinergic drugs are a class of drugs for the treatment of many diseases, including allergy, cold, hypertension, depression, Parkinson's disease, epilepsy, chronic obstructive pulmonary disease, urinary incontinence and overactive bladder. Some of the strongest anticholinergic drugs include antihistamines, hypnotics, tricyclic antidepressants and drugs for overactive bladder. Diphenhydramine hydrochloride is an over-the-counter anti allergic drug. It is mainly used for skin and mucous membrane allergy, such as urticaria, allergic rhinitis, skin pruritus and drug eruption. It is also effective for insect bite and contact rhinitis; The product can also be used for the prevention and treatment of motion sickness and has a strong antiemetic effect.