Diphenhydramine is a generation of antihistamine with antihistamine H1 receptor effect, strong inhibitory effect on central nervous system, and atropine-like effect. It is indicated for allergic diseases of the skin mucosa, such as urticaria, kwashiorkor fever, allergic rhinitis, etc. It can also be used to prevent motion sickness such as seasickness, motion sickness and airsickness. Drowsiness and dry mouth are its main adverse effects. The dosage forms are tablet 25mg, 50mg, injection 20mg, 1mL, cream 20g. Contraindications include contraindication for newborns, premature babies, early pregnancy and lactating women, and contraindication for patients with angle-closure glaucoma.