If your nail has ever turned green or you've experienced mold, the first thing you want to do is scream! You're nervous and concerned. Bacteria can form under a nail treatment primarily for two reasons. The first reason is that the nail is not cleaned properly or has moisture on it before applying the treatment. We recommend using hand sanitizer and allowing it to completely dry before you begin your application. The second reason is due to the nail not being sealed properly during application. If the nail is not properly sealed, water can get trapped on the nail underneath the treatment which can cause bacteria to grow. If you are experiencing this, we would recommend that you consult with your primary care physician for further treatment, if necessary.