Onychophagia (Nail Biting)
Nail-biting can be a temporary, relatively non-destructive 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 some other related behaviors such as lip biting or cheek chewing, onychophagia is classified in the DSM-5 as “body-focused repetitive behavior disorder,” which falls under “Other Specified Obsessive-Compulsive and Related Disorders.” 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, cuticles, and the surrounding skin, may occur on its own or may co-occur with other body-focused repetitive behaviors (BFRBs), such as hair pulling (trichotillomania) or skin picking (excoriation disorder). Symptoms of onychophagia are both psychological and physical. In addition to a compulsive urge to bite their nails, 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, anxiety, or guilt, often related to the appearance of physical damage to skin and nails caused by biting
- fear of others seeing one's nails or being disgusted by them
- strained or complicated family and social relationships, either due to intentional social withdrawal or to others shaming or mocking the individual for the behavior
- tissue damage to fingers, nails, and cuticles
- mouth injuries, dental problems, abscesses, and infections
Nail-biting may occur without conscious notice or may be a focused behavior. It usually begins in early childhood and intensifies during adolescence. Although it may continue through adulthood, the behavior most often decreases with age; in many cases, it stops altogether in late adolescence or early adulthood.
Nail-biting itself is relatively common, but the line between “normal” and pathological nail-biting is not always clear. According to the DSM-5, diagnosable “body-focused repetitive behavior disorder” (a category that includes onychophagia) triggers clinically significant distress, interferes with functioning in at least one important life domain, and is characterized by repeated, failed attempts to stop the behaviors. Thus, those who feel intense shame, guilt, or anxiety about their nail-biting, feel unable to stop, and find that it interferes with one or more areas of their life may benefit from seeking treatment.
Possible physical side effects of nail-biting include damaged or disfigured nails and skin, skin infections, fungal infections, and mouth pain or tooth damage. Individuals who swallow the bitten nails may be at risk for stomach or intestinal infections as well. Because nails and fingers often carry bacteria or viruses, biting them may transmit pathogens into the body, potentially increasing the risk of internal infections or gastrointestinal problems.
Serious or long-term damage from nail-biting is rare but possible. Fingernails themselves are resilient, and biting has been found to have little long-term effect on growth once the behavior has been stopped. Infections to the skin, stomach, or intestines pose the greatest long-term risk but are usually treatable. In some cases, nail-biting may lead to tooth damage (such as chipped teeth) that will require corrective care.
Nail-biting usually begins in childhood, typically after age 3 or 4. It is less common for children younger than 3 to bite their nails persistently. Nail-biting may also begin in adolescence; in very rare cases, an adult may start to bite their nails suddenly.
Nail-biting is thought to be the most common of the body-focused repetitive behaviors. The most commonly cited research studies estimate that 20 to 30 percent of the population bite their nails. Children and adolescents are most prone to nail-biting, with some estimates suggesting that almost 40 percent of children and nearly half of teenagers bite their nails.
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 frequently 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.
Why some individuals bite their nails and others do not is not fully understood. Like other BFRBs, nail-biting appears to run in families to some degree, and may share neurological roots with OCD, anxiety, and other mental health disorders. Some researchers also speculate that nail-biting may partially stem from an overall tendency toward perfectionism in one’s personality, or from a desire to seek stimulation when bored or frustrated. Nail-biting that begins suddenly in adulthood may be the side effect of a medication.
Individuals who bite their nails report many different triggers for doing so. Some bite when anxious or stressed, for example, others bite when bored or understimulated, and still others bite when they’re mentally engrossed in another activity. Identifying one’s own triggers and establishing replacement behaviors is often a critical part of effective treatment.
Old-fashioned remedies specifically designed to prevent nail biting, such as applying bitter-tasting products to the nails, work for some nail-biters—especially those whose habit is less severe—but are usually less effective for those with persistent, compulsive onychophagia. Barrier-type interventions that block contact between the mouth and nails, such as gloves, mittens, socks, and retainer-style or bite-plate devices may be more effective because they both serve as impediments to biting and as physical reminders not to bite. However, they may be challenging to use consistently or over the long term.
In more severe cases of onychophagia, professional treatment can be helpful, especially if it focuses on identifying triggers and managing the emotional factors associated with nail biting. Cognitive behavioral therapy (CBT)—often combined with habit-reversal training and/or progressive muscle relaxation—and acceptance and commitment therapy (ACT) 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.
Yes. Therapy, especially CBT or ACT, can help someone identify and manage the repetitive thoughts or emotional triggers that drive nail-biting. A specific form of therapy known as habit reversal training (HRT) focuses on becoming aware of one’s biting triggers, identifying replacement behaviors (such as balling one’s fists or squeezing a stress ball), and cultivating social support. HRT has been shown to be highly effective in treating BFRBs, especially in the short-term—over the long-term, more comprehensive approaches that include a cognitive-behavioral element are typically most effective.
Medications are not often used for nail-biting, though some patients prescribed SSRIs for anxiety and depression find that the medication reduces their nail-biting somewhat. Some small studies suggest that N-acetylcysteine, a supplement also being investigated for trichotillomania and excoriation disorder, is more effective at reducing nail-biting behaviors than a placebo, though more research is likely needed.
Hiding one's nails or making them unpleasant to bite—by cutting them short, painting them with bitter-tasting polish, or wearing gloves or mittens—can make it more difficult to engage in the behavior. It’s also helpful to identify one’s “trigger”—the emotion or situation that makes someone most prone to biting—and developing coping mechanisms that replace nail-biting with a healthier alternative. For example, someone who bites while bored could play with a fidget toy in situations where they’re likely to be bored; someone who bites when anxious could squeeze a stress ball or engage in a brief relaxation exercise instead of biting.