ProPublica has an in-depth story about the hidden dangers of over-the-counter drugs, especially Tylenol. One of the key problems with Tylenol is that it doesn't take all that many extra pills to start experiencing harmful side effects. For instance, the maximum recommended daily dose is eight extra-strength tablets. Just two additional tablets a day, taken over a long period, can cause liver damage. All told, this isn't a massive risk — about 150 people die from Tylenol poisoning a year — but it does illustrate why you can't assume there are no risks, just because it's easy to buy something.