Sinus infections, the cause of untold misery, strike about 37 million people in the U.S. each year.
On the surface of things, the cause of sinus trouble is clear. Teeny holes that connect your nasal passages to your sinuses (basically a collection of hollow, moist cavities that lurk beneath your nose, eyes, and cheeks) get blocked. Then gunk builds up in your sinuses, germs may grow, and you feel, well, hideous.
But the cause of the blockage is sometimes trickier to figure out. Here are 13 things that can cause an acute sinus infection (the most common type) and, in some cases, lead to a chronic sinus infection.