Reasons for nail biting include stress, nervousness and boredom. It can be a learned behavior and is occasionally a symptom of obsessive compulsive disorder. A person may bite his nails without thinking about it or while performing another activity.
Nail biting refers to biting the nail, the cuticle or the soft tissue around the nail. It is most common with children going through puberty. It is less common among young adults, and it occurs rarely among adults aged 30 or older. It's more common than other nervous habits, such as nose picking and teeth grinding. Nail biting increases infection risk around the nails and mouth. It can cause nail deformities.