Tylenol is one of over 100 brand names of the analgesic acetaminophen that acts quickly and safely to provide temporary relief of minor headaches, minor muscular aches, overexertion, menstrual cramps, and many other ailments. Acetaminophen is available without a prescription, and is widely used either by itself or in combination with other drugs to produce a wide variety of effects. Side effects include yellow eyes or skin, diarrhea, loss of appetite, nausea, and swelling.