Why do we bite nails?

Nail biting, also known as onychophagia, is a common habit for many people. It involves using the teeth to bite, chew, or pick at the nails on the fingers and/or toes. For some, it is an occasional nervous habit, while for others it can be a chronic behavior that is difficult to stop. Nail biting has a number of proposed causes and risk factors. Understanding why people start and continue biting their nails can help identify ways to manage or stop this habit.

Prevalence of Nail Biting

Nail biting is a very common habit, especially among children and adolescents. Some key statistics on the prevalence of nail biting include:

  • Approximately 20-30% of children ages 7-10 years old bite their nails regularly.
  • The prevalence decreases with age; around 10-15% of adolescents still regularly bite their nails.
  • 5-10% of adults bite their nails on a regular basis.
  • Nail biting tends to be more common in males than females across age groups.

These rates indicate that nail biting is one of the most common “nervous habits” and compulsive behaviors. The majority of nail biters begin during childhood. While many kick the habit as they get older, it does persist at a lower rate into adulthood for some people.

Proposed Causes of Nail Biting

There are a number of theories as to what causes people to start, continue, and relapse into nail biting behaviors. Some of the main proposed causes include:

Genetics and Biology

There may be underlying genetic, neurobiological and family dispositions that make some more prone to developing nail biting habits and having difficulty stopping. Research has linked nail biting behaviors with:

  • Hereditary factors – having parents who also bite/picked their nails
  • Underlying neurobiological traits involving brain circuits and neurotransmitters
  • Impulsivity as a personality trait
  • Obsessive-compulsive tendencies

The body may also become dependent on the physical sensations associated with nail biting over time. This can lead to a psychological and physiological reinforcement of the behavior.

Stress and Anxiety

Nail biting is very commonly linked as a reaction to stress, anxiety, tension, nervousness, and other negative emotional states. Possible explanations for this association include:

  • Biting nails provides temporary physical relief from tension
  • It can be an unconscious distraction or diversion from emotional distress
  • The habit develops as a learned coping mechanism to deal with emotional difficulties

Nail biting then becomes reinforced over time as a habitual way to self-soothe when anxious. This makes the behavior more likely to persist and resurface when under stress.


Nail biting is also associated with boredom and the need for stimulation. Possible links include:

  • Biting nails provides physical stimulation when bored
  • It becomes an unconscious habit to fill time and distract from boredom
  • The behavior provides temporary sensory interest

Similar to stress, nail biting can then become reinforced as a response to bored situations over time. This makes it become an automatic behavior whenever bored.

Social Learning

Observing and copying the behavior from parents or peers is also a potential contributor, especially during childhood. If children regularly see others biting nails, they are more inclined to try it themselves and turn it into a learned habit over time.

Risk Factors

Certain characteristics and circumstances seem to be linked with higher risks of beginning and maintaining nail biting habits:


Nail biting typically begins during childhood, around ages 5-10 years old. Younger children are more susceptible to picking up the habit from parents or peers. It also reflects a developmental period where nail biting may be used to self-soothe during emotional upsets or satisfy stimulation needs. Adolescence is the next most common period for nail biting to emerge.


Males, especially boys, tend to exhibit higher rates of nail biting across age groups when compared to females. This may relate to innate gender differences in typical personality traits and coping mechanisms.

Mental health conditions

People with certain conditions appear more predisposed to chronic nail biting, including:

  • Anxiety disorders
  • Obsessive-compulsive disorder
  • Autism spectrum disorders
  • Attention-deficit/hyperactivity disorder (ADHD)

The habit may develop as a symptom or coping mechanism related to the condition. Underlying neurobiology or genetics could also make nail biting more likely.

High stress levels

Those undergoing high levels of psychological stress or instability seem to exhibit more nail biting habits, especially if they lack healthier coping skills. Examples include stressful family situations, school and work pressures, financial problems, or relationship conflicts.


Habitual nail biting tends to be more common in those who frequently experience boredom or have idle time. Without other stimuli or activities to engage in, nail biting can become a default behavior to fill the time and provide sensory stimulation.

Physical Effects of Nail Biting

Regular nail biting over time can lead to various physical effects and complications. Potential consequences include:

Damage to nails

Constant biting can cause nails to become ragged, uneven, splintered, thin, and brittle. This can lead to pain as well as cosmetic concerns. Damaged nails are also breeding grounds for infection.


Opening the skin around the nails provides pathways for bacteria and viruses to enter and cause infections of the fingernails or cuticles, known as paronychia. Ingrown toenails are also a possible complication. Oral infections could also develop from bacteria, viruses or fungi entering the mouth during biting.

Dental problems

Biting fingernails can chip and crack teeth. It can also trigger teeth misalignment and changes to the roof of the mouth over time.

Digestive issues

Swallowing nail fragments or filings when biting off nails could cause physical irritation, inflammation, or injury within the digestive tract.

Spread of pinworm

The contagious pinworm parasite infection can spread through nail biting when infected fingers enter the mouth. This is most common in children.

Physical Effects Examples
Damage to nails Ragged, uneven, brittle, thin nails
Infections Paronychia, ingrown nails, oral infections
Dental problems Chipped/cracked teeth, misaligned teeth, changes to roof of mouth
Digestive issues Irritation, inflammation or injury from swallowing nail parts
Spread of pinworm infection Contagious parasitic infection entering mouth from fingers

Psychological Effects of Nail Biting

In addition to physical effects, habitual nail biting may also have psychological consequences:

Emotional distress

Some individuals, especially adolescents, may experience significant shame, anxiety, and reduced self-esteem related to their nail biting if it causes embarrassment or impacts appearance. There is also potential distress if they want to stop but are unable to.

Social difficulties

Extreme or socially inappropriate nail biting in public can negatively impact social interactions and relationships. There may be social anxiety or avoidance related to embarrassment of the habit. Colleagues or bullying peers may also tease or isolate nail biters, especially children.

Self-image issues

Body-focused repetitive behaviors like nail biting contradict a person’s self-image of having control over behaviors and appearance. This can lower self-confidence and increase focus on physical appearance instead of inner positive traits.

Reduced productivity

In severe cases, chronic nail biting may interfere with daily functioning, ability to concentrate, successfully complete tasks, or achieve goals. Frequent nail biting breaks distract from work or school activities.

When Nail Biting Becomes Problematic

Most occasional, mild nail biting does not cause serious health issues or interfere with life. However, chronic, severe nail biting can become highly problematic. Signs it may require professional treatment include:

  • Persistent biting daily or almost daily for 6+ months
  • Severe damage to the nails and skin around nails
  • Bleeding, pain, infection, or physical injury
  • Significant social or emotional distress
  • Interferes with daily life and responsibilities
  • Unable to stop or reduce frequency despite making efforts

Seeking professional help is advisable in these problematic cases where nail biting has become excessive and caused impairment or harm. Assessment and treatment from a doctor, therapist, or counselor can improve management of this challenging habit.

Treatments to Stop Nail Biting

A number of techniques and interventions may help reduce or eliminate chronic nail biting habits:

Behavioral therapies

Working with a therapist, several behavioral approaches aim to make patients more aware of their habits and triggers, and develop skills to change nail biting behaviors. Common behavioral strategies include:

  • Cognitive-behavioral therapy – identifying distorted thoughts that maintain the behavior and learning healthier coping skills.
  • Habit reversal training – manually interrupting the habit and substituting with an alternate action.
  • Stimulus control therapy – removing triggers and modifying surroundings to make nail biting less accessible.


Prescription medications may help reduce nail biting driven by underlying psychiatric conditions such as anxiety disorders, OCD, or ADHD. Anti-anxiety medications, antidepressants, or other psychological medications can address root causes.

Barrier techniques

Applying bandages, tape, gross-tasting polishes or false nails to fingers can act as physical barriers to biting nails. However, these are temporary and don’t change the root habit.

Alternative techniques

Methods like acupuncture, hypnosis, yoga, or meditation may help relax the body, reduce anxiety and boredom, increase self-awareness, and ultimately decrease nail biting for some people. But more research is needed on their effectiveness.

Tips to Stop Biting Nails

Along with professional treatment methods, some self-help tips to help reduce nail biting include:

  • Keeping nails trimmed short to limit biting opportunities
  • Carrying a stress ball or fidget toy to occupy hands when tempted
  • Identifying and managing triggers like stress or boredom
  • Finding other oral habits like chewing gum to substitute
  • Using bad tasting polishes or bandages to remind against biting
  • Rewarding progress for going longer without biting nails

Developing more awareness of when and why biting occurs, and having strategies to redirect the habit, can help some gain control over frequent nail biting.

Preventing Nail Biting in Children

For parents seeking to prevent nail biting in children, key tips include:

  • Modeling – making sure parents and other family avoid nail biting themselves
  • Providing activities for idle hands when bored
  • Not punishing for nail biting, but praising for progress stopping
  • Encouraging open communication about any stress/anxiety
  • Suggesting alternatives like rubbing hands together or playing with putty
  • Keeping nails trimmed short to limit damage if biting persists

With patience and support, many children can overcome nail biting habits over time. Seeking additional help from school counselors or therapists is recommended if the behavior persists and causes distress.


Nail biting is a common oral habit with a number of underlying causes including genetics, anxiety, boredom, and social learning. It can have physical and psychological effects, especially when severe and chronic. While difficult to stop, nail biting can often be reduced through therapies, behavior changes, and habit substitutions. Addressing root factors like stress can also help. With time and consistency, the bothersome habit can be overcome. Keeping an open, non-judgmental approach and not punishing lapses are key to long-term success.

Leave a Comment