 If you haven't washed your pillowcase in the last 3 days, you might as well be sleeping on your toilet seat. Yup, after a week, your pillowcase is full of 3 million colony forming units of bacteria. That's 17,000 times more bacteria than the porcelain throne. Some of that bacteria can lead to different kinds of infections and even pneumonia. Not to mention the dead skin cells and sweat that lured dust mites to your pillow. You can keep your pillowcase cleaner by washing it and yourself regularly.