What Is the Strongest Over-the-Counter Sleep Aid?

There is no real way to quantify strength among over-the-counter sleep aids; however, the most popular sleep aids include those that contain diphenhydramine, which is an antihistamine that is useful in promoting sleep due to its sedating properties. Mayo Clinic states that a number of OTC sleep aids contain diphenhydramine, including Unisom Sleep Gels, Tylenol PM and others.