Nail biting can be a temporary, relatively nondestructive behavior that is merely a cosmetic concern, but it can also develop into a severe, long-term problem. Onychophagia, or onychophagy, is considered a pathological oral habit and grooming disorder characterized by chronic, seemingly uncontrollable nail biting that is destructive to fingernails and the surrounding tissue. Along with other body-focused repetitive behaviors (BFRBs), onychophagia is classified in the DSM-5 as an “Other Specified Obsessive-Compulsive and Related Disorder.” Professional treatment, when necessary, focuses on both the physical and psychological factors involved in nail biting.
Onychophagia, which often results in visible damage to fingernails, may co-occur with other BFRBs, such as hair pulling or skin picking. Symptoms are both psychological and physical. People who chronically bite their nails may experience:
- distressful feelings of unease or tension prior to biting
- feelings of relief or even pleasure after biting
- feelings of shame, embarrassment, and guilt, often related to the appearance of physical damage to skin and nails caused by biting
- tissue damage to fingers, nails, and cuticles
- mouth injuries, dental problems, abscesses, and infections
- in some cases, onychophagia may lead to complicated family and social relationships
There may be a genetic link to onychophagia; some people appear to have an inherited tendency toward developing BFRBs, as well as higher-than-average rates of mood and anxiety disorders in immediate family members. Nail biting is associated with anxiety, because the act of chewing on nails reportedly relieves stress, tension, or boredom. People who habitually bite their nails often report that they do so when they feel nervous, bored, lonely, or even hungry. Nail biting can also be a habit transferred from earlier thumb or finger sucking. While nail biting can occur without symptoms of another psychiatric condition, it can be associated with Attention-Deficit/Hyperactivity Disorder (ADHD), oppositional defiant disorder, separation anxiety, enuresis, tic disorder, and other mental health issues.
Old-fashioned remedies specifically designed to prevent nail biting, such as applying bitter-tasting products to the nails, are generally ineffective. Barrier-type interventions that block contact between the mouth and nails, such as gloves, mittens, socks, and retainer-style or bite-plate devices can serve as impediments to biting or reminders not to bite. Treatment in severe cases must also focus on reducing or removing the emotional factors associated with nail biting. Cognitive behavioral therapy (CBT), with habit-reversal training and progressive muscle relaxation, and acceptance and commitment therapy (ACT), along with a self-help technique known as movement decoupling, have been shown to be beneficial in some cases of BFRBs. Any successful treatment of onychophagia requires the permission and cooperation of the child or adult who is biting their nails, along with positive reinforcement and routine follow-ups.