You might have heard of gua sha, which is basically a scraping massage. It’s often used as part of acupuncture therapy, employed to treat acute disease, from fever and migraine to hepatitis. It has been gaining interest as a facial treatment among American beauty junkies, who claim that gua sha can firm muscles, smooth skin and lighten age spots. What is gua sha, and does it work? For this week’s Healthy Habit, I set out to find out.