Stop biting of finger nails

Onychophagia, or nail biting, is a pretty common habit, affecting an estimated 30 percent of adults, 45 percent of teens, and 30 percent of children.
Nail biting can be caused by stress, anxiety, obsessive compulsive disorder, or just being bored and fidgety and all these can seem harmless, but you should know that it can invite bacteria or fungi infections to enter into the body and blood stream, increasing your chances of contracting a cold or the flu.
1. How nail biting leads to cold and flu

According to the CDC, there are more than 200 cold viruses floating around at any given time. Even though the risk factors for acquiring one include a weakened immune system and/or exposure to someone sick, you can significantly reduce your chances of catching a virus by keeping your hands away from your mouth.
Viruses that cause the flu also flourish on your skin, so wash your hands frequently with soap and water (or use an alcohol-based hand sanitizer), and discourage nail biting by chewing gum.
2. How nail biting can harm your teeth
Nail biting can also damage your teeth and gums. The Academy of General Dentistry has found that nail biting can crack, chip, or wear down the front teeth, and also potentially lead to sore gums and gum tissue damage.
You may want to ask your dentist about having a mouth guard which can help you to stop biting your nails—or at least minimize some of the damage it can cause. They may also help to suggest some other techniques to help you quit the habit for good.