Nail biting is one of the most common things that people do when they fidget. It is most common during adolescence due to puberty, and nail biting could be a manifestation of stress. Though many adolescents outgrow the habit, there are still many adults who bite their nails in times of stress.
Is nail biting a bad habit? Since it is common, some people believe that it is normal and harmless. This could be true; however, it might also be useful to know that Onychophagia, which is the medical term for nail biting, is listed in both the Diagnostic and Statistical Manual of Mental Disorders (DSM) and the International Classification of Diseases (ICD) as a form of compulsive, repetitive, maladaptive, and/or abnormal behavior.
Nevertheless, do not be overly concerned and jump to the conclusion that you have a severe issue that needs to be fixed if you have a habit of nail biting. Onychophagia is only considered abnormal and/or maladaptive if the habit is excessive and interferes with normal, regular, and daily functioning.
If you believe that you or someone you know has developed an excessive and maladaptive form of nail biting, you should inform your medical practitioners as they will know how to help you better.