'Tis the season to have the sniffles. It gets pretty annoying when you can only breathe out of one nostril. But as this video from Australian radio station Triple J explains, there's actually a simple scientific explanation why one side is always clogged: Your nose has erectile tissue, just like the penis or clitoris. The tissue is on a cycle that causes one side of your nose to swell at a time. That's what causes the alternating flow of air—and snot. The more you know, right?