Many people have trouble falling asleep or staying asleep and find that taking medications can help them get better sleep at night. Tylenol PM is a relatively mild over-the-counter sleep aid that consists of tylenol (a pain reliever) and benadryl (an anti-histamine). Most of the sleep aid effect of Tylenol PM comes from the benadryl, as anti-histamines are known to make people sleepy. In fact, some of the early prescription allergy medications were not well-tolerated by patients because of this side effect. The manufacturers of Tylenol PM are simply taking advantage of this side effect in packaging the benadryl with the tylenol.
In general, neither Tylenol nor benadryl or particularly dangerous or addictive medications. However, it is also good to keep in mind that even if your body is not 'addicted' to a sleeping pill in the same way that we would use the term addicted in the context of something like a narcotic medication, you may very well develop a dependence on the medication. For this reason, it may be a good idea to try limiting the Tylenol PM only for those days when you truly can't fall asleep. The medication itself won't hurt you, but it might keep you from developing more healthy sleep habits. Your primary care doctor
can talk with you about good sleep hygiene habits, and this plus the Tylenol PM when you need it can help keep you sleeping through the night.