ZzzQuil vs. Benadryl: what’s the difference? The classic ZzzQuil Nighttime Sleep-Aid and Benadryl contain the same active ingredient: diphenhydramine. One is marketed for sleep and one for allergies, but always check the active ingredient on the label because there are different ZzzQuil products now. #ZzzQuil #Benadryl #Diphenhydramine #SleepAid #PharmacistTips