Why Does Benadryl Make You Sleep?
Benadryl and other allergy drugs contain a natural chemical known as diphenhydramine, an histamine blocker that helps treat allergy reaction, motion sickness, and some symptoms of cold. Antihistamine became popular in the 1940s.
It is important to note that there are other drugs that contain diphenhydramine. The ingredient can also be found in some nighttime drugs, such as Advil PM, Tylenol PM, or Sudafed’s day/night cold medicine. According to studies, the amount of diphenhydramine in Antihistamine Nighttime increases from 25mg to 50mg.
Caffeine is a major ingredient of many “daytime” pain relievers. Taking any of these drugs will keep you awake at night. The nighttime version of these drugs do not contain caffeine, but they contain diphenhydramine which helps reduce pain and induced sleep. While antihistamine causes drowsiness, it is not effective for treating insomnia.