Why should I choose Nytol One-A-Night? Nytol One-A-Night may be a good choice for you if you’ve used sleeping aids in the past, or are looking for a convenient dose as part of your bedtime routine. Simply taking a single tablet 20 minutes before bed can help you drift off, improving the depth and quality of your sleep. How does Nytol One-A-Night work? Let’s get a little sciencey for a second. Nytol One-A-Night contains a commonly used antihistamine called diphenhydramine hydrochloride (trust us it’s easier to use than to say!) It works by blocking the normal actions of histamine, the chemical that stimulates arousal-promoting areas of the brain. This helps reduce alertness and promote that first drowsy stage of sleep, helping you to then drift off into a restful, deeper sleep.