The Scientist: Rebecca Booth, M.D., is an obstetrician and gynecologist who practices in Louisville, Kentucky. She is the author of The Venus Week: Discover the Powerful Secret of Your Cycle…At Any Age.The Answer: Toxic shock syndrome may seem like an urban legend. (Have you every known anyone who actually got it?) But make no mistake, T.S.S. is definitely real. It’s just really rare. There are between one and 17 cases per 100,000 people.T.S.S. has a number of possible causes, but it’s most infamous is keeping tampons in for too long. You should always change your tampon every four to six hours. That means you shouldn’t sleep with it in.