“Using toothpaste for acne typically does more harm than good,” says S. Tyler Hollmig, MD, the director of laser and cosmetic dermatology at the University of Texas at Austin’s Dell Medical School.

Is it true that toothpaste can treat pimples? Toothpaste is being touted on social media as a hack to clear acne, soothe burns and whiten fingernails. But dermatologists say products intended for ...