Nytol one a night is used to relieve temporary sleeping difficulties. The active ingredient contained within nytol diphenhydramine hydrochloride is an antihistamine that causes sleepiness drowsiness. Sleeping difficulties can be caused due to many reasons such as jet lag, stress, personal problems and by taking nytol it is an aid to a good nights sleep. Nytol one a night has been proven to help you fall asleep faster and have a longer, deeper sleep leaving you feeling fresh and rested in the morning.adults over 16 years and elderly 1 tablet 20 minutes before going to bed. Under 16 years and children not to be given.you should make sure that you carefully read all product packaging and labels prior to usedo not use in the following cases asthma, narrow angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal and bladder neck obstruction, pregnancy, lactation or if taking cns depressants or maois. Use with caution in cases if myasthenia gravis and seizure disorders. Driving and use of machinery should be avoided as nytol causes drowsiness. Avoid alcohol.