There are many, many different skin-care products out there...and keeping skin healthy has long been a booming industry...but how did we get here? And why are there so many confusing messages from health experts regarding the care of our skin? Why are there so many ineffective treatments? Our guest is a preventative medicine physician and staff writer for The Atlantic whose new book explains the surprising (and often unintended) effects of our modern-day hygiene practices; his book also offers an introduction to the new science of skin microbes and probiotics. James Hamblin is our guest, and his book is called "Clean." As noted by a critic for BookPage: "A fascinating, rich mix of science, marketing, and culture that will have you questioning everything you think you know about your daily skincare routine."