Cetirizine, or Cetirizine Hydrochloride, there is no optimal time to take Cetirizine Hydrochloride, it is usually taken at bedtime or after meals. Cetirizine hydrochloride is an anti-allergy drug, mainly used for hives, allergic rhinitis and other allergic diseases treatment. In order for patients to get a good night’s sleep and avoid allergies interfering with sleep, it is generally recommended to take Cetirizine Hydrochloride half an hour or one hour before bedtime. Cetirizine Hydrochloride can also be taken immediately after meals if allergy symptoms are more severe. Cetirizine Hydrochloride has some efficacy, and taking Cetirizine Hydrochloride may cause adverse reactions such as dry mouth, emotional instability, headache, nausea, diarrhea, and drowsiness. It is prohibited for those who are allergic to Cetirizine Hydrochloride and Hydroxyzine, prohibited during pregnancy, lactation and the presence of severe renal impairment patients, and should not be taken after drinking alcohol. Taking Cetirizine Hydrochloride should be guided by a doctor and should not be used blindly.