Diphenhydramine is an ethanolamine antihistamine, which is mainly used for the treatment of allergic diseases and counteracts or attenuates the effects of histamine on vascular, gastrointestinal and bronchial smooth muscles. It has a strong inhibitory effect on the central nervous system. It also has antiemetic and anticholinergic effects, and is mainly used for motion sickness, motion sickness, etc. Adverse reactions include dizziness, headache, drowsiness, dry mouth, nausea and sleepiness, which can disappear after stopping or reducing the drug. It can also cause skin rash, granulocytopenia, and anemia after long-term application for more than six months. Therefore, the drug should be used under the guidance of a doctor during the process of administration. In addition, routine blood monitoring is required, and once there are changes in the blood, the drug should be stopped immediately or changed to other drugs.