Biting your nails is unsanitary and can damage the skin around the nail, increasing the risk of infection, and harm teeth. To stop nail-biting, the Mayo Clinic recommends the following: avoid factors that trigger nail-biting; take steps to manage stress and anxiety; keep your nails neatly trimmed; occupy your hands or mouth, such as by chewing gum; and apply a bitter-tasting lacquer to nails. If you’re concerned about nail-biting, consider talking to a doctor or mental health professional. Mayo Clinic, June 2019