8. Biting nails
Some people have the unhealthy habit of biting their nails either to keep them short or because of nervous reactions. In as much as it does not seem there is much to worry about, it comes with health risks such as getting bacterial infection, with bacteria coming from the nail to the mouth. It also causes nail infections around the nails and even causes dental problems such as lack of proper coming together of teeth due to having nails in the mouth all the time.