If there's one drug that's taken for granted, it's aspirin. Even though most of us have a bottle in our medicine cabinet, there's a lot about it we don't know. Here are a few interesting facts about aspirin, courtesy of U.S. News & World Report:To start with, aspirin has been around a long time. As early as 400 B.C., Hippocrates prescribed willow leaves to reduce pain. Guess what? Willow bark and leaves contain an acid that's the active ingredient in aspirin. A couple of thousand years later, a man named Edward Stone discovered that willow powder also reduced fevers. Unfortunately, the acid is so harsh that it's used in over-the-counter wart removers. It took scientists another two centuries to figure out how to buffer aspirin it so it wouldn't cause stomach problems. Here are a few recent discoveries about aspirin:* deafness by one third. Aspirin can still cause stomach problems that include nausea and even internal bleeding. So, while it's safe for most adults to use aspirin on occasion, the Mayo Clinic recommends you treat aspirin like any other medication and ask your doctor before using it on a daily basis.