Studies show that 60 percent of children and nearly half of teenagers bite their nails, and the habit doesn’t always disappear in adulthood. Nail biting in adults is recognized as a mental health issue, a manifestation of compulsive grooming like trichotillomania, compulsive air-pulling. Compulsive grooming is recognized as a form of obsessive-compulsive disorder. However, people seldom think of it in these terms; biting the nails is generally looked upon as a mere harmless habit. In fact, the apparent harmlessness makes it difficult to get a good idea of how many people do bite their nails—because people may not think about it and almost never seek treatment for it, the number of people with a nail-biting habit is almost certainly significantly underreported.
However, while it may seem harmless to bite ones nails, it isn’t. Sometimes this is obvious, such as when someone bites so much that their cuticles bleed. But there are more subtle dangers as well. Nail biting brings the fingers to the mouth. That much is obvious, but along with the fingers comes whatever they may have been touching recently—subway poles or bus straps, the roof of a gar, a toilet handle, raw meat, whatever it may be, and with that comes all manner of harmful things. In addition, the skin around the nails can break without necessarily causing bleeding, and even without blood, any of those microbes can cause an infections. When the nails are bitten down, they are unable to do their job of protecting the fingertip, so biting nails increases the risk of damage there.
Sometimes nail-biting, rather than obsessive-compulsive disorder, can be a sign of a different mental health problem, such as anxiety. In these cases, treating that will generally stop or significantly reduce nail-biting. Obsessive-compulsive disorder treatments might also, but there are more direct methods as well. Managing stress and avoiding boredom can work wonders. Chewing gum or doing something else to keep the mouth busy can also cut down on nail-biting. Sometimes, drastic measures might be needed. A substance called denatonium benzoate is the foulest-tasting substance known. Spreading it on the nails can be a powerful aversive therapy tool, stopping the nail biter long enough for the habit to be broken. This, and variations with less awful (though still bad) tastes, is the most common clinical remedy for biting the nails.