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Dangers de se ronger les ongles.

Biting your nails: what are the risks?

Sucking one's thumb, picking one's nose, twisting one's hair, grinding and clenching teeth... compulsively biting nails, commonly referred to as onychophagia, is among the most common behaviours in the category of "typical nervous habits". Often regarded as nothing more than a boredom habit and too frequently overlooked, this behaviour can lead to health issues. Let's explore which ones in this article.


Biting one's nails: why do some people develop such a habit?

Onychophagia is characterised by thecompulsive urge to bite one's nails, often leading to tissue damage to the nails, cuticles, and surrounding skin. This can range from occasional mild behaviour to profound self-mutilation. It typically involves the soft tissues surrounding the nail, the cuticle, as well as the nail itself. Common among children and young adults, it occurs in 20 to 33% of children and nearly 45% of teenagers.

This functional habit is generally not observed before the age of 3 or 4 years. Most cases of nail biting begin in early childhood, between 4 and 6 years, and stabilise from 7 to 10 years before intensifying in adolescence with the onset of puberty. However, in many cases, this behaviour most often decreases with age: it stops spontaneously and completely at the end of adolescence or the beginning of adulthood.

Adults can also fall victim to this, particularly after experiencing high levels of stress at work, undergoing a traumatic event (such as divorce, death, etc), or in cases of withdrawal (from tobacco, alcohol, etc). It has also been observed that boys are significantly more likely than girls to bite their nails.

The reason why some individuals develop or do not develop this particular habit is not entirely clear and understood. However, the need to bite one's nails is generally associated with a psycho-emotional state of anxiety due to the self-soothing effect it provides afterwards. It is seen as a reflex of emotional imbalances : a reaction to stress, fear or excessive depression. Our emotional makeup (shyness, low self-esteem) also plays an integral part in the reason why we turn to nail biting.

Onychophagy also has a strong correlation with personality. Thus, some impatient individuals or those prone to frustrations often bite their nails frenziedly to channel their excess energy and regulate their emotions. This behaviour can also occur in order to imitate someone, especially observed in children.

Complications arising from biting your nails?

Biting your nails can lead to a number of consequences that should not be overlooked.

  • Dental Anomalies: Non-physiological mechanical forces acting on the teeth can cause enamel abrasion. One can also observe a rotation and small fractures on the incisive edges of the mandibular incisors (lower front teeth), as well as a displacement of the maxillary incisors (upper front teeth). However, if this persists, onychophagy can also cause a misalignment between the upper dental arch and the lower dental arch (dental malocclusion), due to the pressures exerted.

  • Oral afflictions: If your nails are infected (onychomycosis, paronychia) and you bite them, not forgetting that nails are a fertile ground for the development of microorganisms, these can be transmitted from your fingers to your oral cavity. This can then cause an infection (herpes, gum inflammation, etc.). By biting your nails, it is also possible to be infected by pinworms, tapeworms, staphylococcus, salmonella, E. coli and human papillomavirus.

  • Nail Damage: Initially, the damage caused to the nail plate is minimal, but over time, as the habit strengthens, we can observe a deformation and weakening of the nail plate, as well as wounds and bleeding on the fingers. The hands of a person suffering from onychophagy no longer appear aesthetically pleasing. This can be a cause of embarrassment and sometimes even social withdrawal, which intensifies stress and a number of other negative emotions, becoming the reason for the persistence of the habit.

  • Gastrointestinal Infections: Nail biting, being a carrier of microorganisms, can transmit harmful pathogens into the body. Indeed, swallowing bitten nails can pose a risk of gastric or intestinal infection. Consequently, we are threatened by a inflammation of the intestines, liver, and stomach, which can manifest itself, for example, through diarrhoea or acute abdominal pain.

  • Nail Infections: Chronic nail biting can also make you susceptible to various types of infection (onychomycosis, paronychia). You create a cycle of transmitting bacteria, fungi or viruses from your mouth to your fingers, and vice versa. Indeed, nails provide a conducive environment for the growth and proliferation of potential pathogens. Thus, by biting your nails and cuticles, you are giving free access to all microorganisms.

    They can penetrate through cuts, and consequently, cause damage (pain, irritation, redness, purulent wounds, etc.) to the surrounding skin, as well as to the nail plate. Similarly, a person who bites their nails and suffers from oral herpes can develop herpetic whitlow on the bitten finger. Moreover, once the infection has reached the fingertips, it can spread to other parts of the body.

For these various reasons, it is therefore crucial to take measures to gradually correct this habit.

Anecdote : A positive aspect of nail-biting is that it does not delay nail growth. On the contrary, it increases nail growth, perhaps because frequent manipulation of the nail stimulates blood circulation in the nail root.


  • PENNINGTON L. A. Prevalence of nail biting among adults. American Journal of Psychiatry (1945).

  • KLEIN E. T. Pressure Habit, Etiological Factors in Malocclusion. American Journal of Orthodontics and Dentofacial Orthopedics (1952).

  • ROYALL L. R. & co. Manifest anxiety and nail-biting. Journal of Clinical Psychology (1974).

  • BRASTTSTROM V. & al. Nail biting: Frequency and association with root resorption during orthodontic treatment. British Journal of Orthodontics (1985).

  • ROBSON L. M. & others. Nail biting. Clinical Paediatrics (1990).

  • CAMARGO E. S. & al. Nail biting, or onychophagia: A unique habit. American Journal of Orthodontics and Dentofacial Orthopedics (2008).

  • GHANDIZADEH A. Nail Biting; Causes, Effects and Management. Iranian Journal of Medical Sciences (2011).

  • DEMETROVICS Z. & al. Pathological grooming: Evidence for a single factor behind trichotillomania, skin picking and nail biting. PLoS One (2017).

  • SIDDIQUI J. Onychophagia (nail biting): an overview. Indian Journal of Mental Health (2020).

  • KIM M.-B. & al. Onychophagia: detailed clinical characteristics. International Journal of Dermatology (2022).


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