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Why Do I Bite My Nails and Do I Have Onychophagia

Why Do I Bite My Nails and Do I Have Onychophagia

Many of us bite our nails once in a while, but if the habit develops into a long-term or severe problem it’s known as a condition called onychophagia.

This is thought to be common in children and young adults, with studies suggesting between 20 - 33 per cent of children and around 45 per cent of teenagers bite their nails (i).   It’s thought that many children and teenagers grow out of the habit, but some continue with nail biting as adults (though because most of the studies into onychophagia are limited to children and teenagers we don’t really know exactly how many adults are affected).

The most obvious symptom of onychophagia is the visible damage it causes. This includes damage to parts of the nail including the following:

  • The nail plate (this is what most people refer to as the nail itself, the hardened covering of the nail bed that’s made from a protein called keratin)

  • The proximal nail fold (the protective fold of skin around the edge of the base of the nail plate)

  • The lateral nail fold (the continuation of the proximinal nail fold along each side of the nail plate)

  • The perionychium (the skin surrounding the nail)

  • The hyponychium (the skin that forms the seal between the nail plate and the nail bed where the growing tip starts)

Besides this tissue damage, people who bite their nails may also experience a range of psychological issues, such as stress or tension before biting, a feeling of relief or even pleasure after biting and also often embarrassment and guilt because of the physical appearance of their nails.

Indeed, onychophagia has been classified as a body-focused repetitive behaviour that’s part of a specified obsessive-compulsive and related disorder in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) (ii), a diagnostic handbook used by many doctors published by the American Psychiatric Association. This classification places nail biting alongside other body-focused repetitive behaviours (BFRBs) such as trichotillomania (compulsive hair pulling) and dermatillomania (compulsive skin picking).

What causes it?

Experts still don’t know exactly what causes nail biting, though it has often been associated with anxiety, with some people who bite their nails reporting it helps relieve stress and tension. Some admit to biting their nails in order to cope with other emotional or mental states such as nervousness, frustration, boredom, insecurity and low mood. It’s not uncommon for people to bite their nails when they feel hungry, or when they’re concentrating deeply, either.

There could also be a case for arguing nail biting is hereditary, since it can run in families – though in such cases it could well be a behaviour children learn from their parents, rather than the result of any genetic link. It may also be a habit that develops out of thumb or finger sucking

Nail biting is also often described as an automatic behaviour, meaning you’re likely to do it without realising. And according to the US-based TLC Foundation for Body-Focused Repetitive Behaviors, it can also be accompanied by other BFRBs including trichotillomania, skin picking disorder, bruxism (teeth clenching or grinding) and cheek biting (iii).

Complications of chronic nail biting

Biting your nails is a socially unaccepted habit, largely because of the way it affects the appearance of your hands. But if you’re a chronic nail biter there are other ways it can affect aspects of your health, including the following:


If you bite your nails severely it can cause tissue damage that can lead to viral, bacterial and fungal infections of the nail bed as well as the surrounding skin.

Temporomandibular dysfunction

The temporomandibular joints connect the jawbone to the skull, and chronic nail biting may affect them, causing a condition called temporomandibular dysfunction (or temporomandibular disorder, TMD for short) (iv). If you have TMD you may experience symptoms such as pain around your jaw, ear and temple, popping or clicking noises when you move your jaw, headache, locking of your jaw and difficulty in opening your mouth fully.


A bone infection that usually affects the legs, arms or back, osteomyelitis has been recorded in the in finger bones of people who bite their nails severely (v). This painful condition can happen when bacteria or fungi spread to bones from infected tissue or an infected wound through the bloodstream. It can cause soreness, redness and swelling in the affected area, and is usually treated with antibiotics or antifungal drugs.

Dental complications

While much of the damage of nail biting is done directly to the nail and surrounding parts of the fingers, constant nail chewing can also have an effect on your teeth and mouth, causing the following:

  • Chipped, worn and broken teeth

  • Malocclusion of the front teeth (that is, when your front teeth aren’t positioned correctly)

  • Crowding and protrusion of the teeth

  • Injury to the soft tissue lining the mouth

  • Gum inflammation and infection

  • Apical root resorption (a condition that can lead to permanent loss of tooth structure)


How to treat onychophagia

If you bite your nails there are several things you could do that may help:

Nail coatings

Liquid compounds that you apply to your nails that make them taste bitter are available over the counter. There’s no clinical evidence they work, but they are often the first thing people try for breaking their nail-biting habit.

Use a barrier

Anything that puts a barrier between your teeth and your nails may be worth a try, such as wearing gloves or mittens, or using oral devices such as mouth guards. These may be particularly helpful if you tend to bite your nails at night – though they may not be practical for daytime use (using something that acts as a nail covering may be more acceptable)

Keep your nails short

The shorter your nails are, the less satisfying biting them may feel – which means cutting them may be useful if you use nail biting as a form of emotional relief. Alternatively, getting a good manicure to make your nails look attractive may make you think twice before you bite.

Keep your mouth occupied

Chewing sugar-free gum may be useful if you need to keep your mouth busy, or you could try a chew tool made from medical-grade materials that are designed to be chewed for stress relief (some of these are made to be worn as necklaces, called chewelry, and are suitable for children and adults). Meanwhile, try to find something to occupy your hands too (squeeze a stress ball, for instance).

If these simple measures aren’t effective, there are some psychological treatments that are sometimes recommended for onychophagia:

Cognitive behavioural therapy (CBT)

This popular talking therapy attempts to change the way you think and behave around a problem, and your therapist may ask you to keep a diary of when you bite your nails to try and discover what triggers the biting. It may also help you find alternative ways of addressing the triggers – for instance, if you bite your nails when you’re feeling stress, you may learn other ways of feeling more relaxed.

CBT is offered on the NHS for a range of physical and mental health issues, but waiting times can be long.

Habit-reversal training (HRT)

HRT involves awareness training, which means working with a therapist to discover which situations or emotions lead you to bite your nails and how biting your nails can have negative consequences. Like CBT it also helps you to find alternative behaviours, ideally those that make it difficult for you to bite your nails (activities that involve using your hands, for example).

Another component of HRT is social support, whereby someone you’re close to points out when you’re biting your nails or gives you encouragement when you use one of your alternative behaviours. However, since habits are often hard to break, HRT needs commitment as it may take a lot of effort.


Some natural health practitioners also recommend hypnotherapy for breaking stress-related habits.

To find a therapist in your area, visit the British Association for Counselling and Psychotherapy’s website. 

Other nail disorders

Biting your nails can dramatically affect their appearance. But there are other things that can change the way your nails look too – here’s a quick guide to some of the most common nail problems:

Thickened nails

Often these can be a sign of a fungal nail infection, though they can also be caused by psoriasis, a form of arthritis called reactive arthritis, and, where toenails are concerned, wearing badly fitting shoes for a long period of time.

Brittle or weak, crumbling nails

These can also be a sign of a fungal nail infection, but often they are a result of exposure to water, detergents and other chemicals such as those found in nail polish. Other conditions that cause brittle, crumbly nails include an underactive or overactive thyroid, nail psoriasis and a skin condition called lichen planus.

Discoloured nails

Nails can turn grey, brown or green-black, but possibly the most common discolouration of nails is yellowing. Again, fungal nail infections and nail psoriasis can be behind this common nail problem. Other things that could cause yellow-coloured nails include sinusitis, jaundice (which turns the skin under the nail plate yellow), tuberculosis, lymphoedema (which causes swelling of the skin) and infection of the nail folds (or perionychium).

Using nail polish for extended periods of time can also discolour your natural nails. Nails that are half white and half brown, on the other hand, may be a sign that your kidneys aren’t working properly.

Nail dents

Pitting or small dents on the surface of the nails can be a sign of psoriasis (it’s thought that up to 50 per cent of people with psoriasis have psoriatic nail disease (vi)). This can also be caused by eczema, reactive arthritis and a type of hair loss called alopecia areata.

Curved nails

This is when there’s a spoon-shaped dent in your nails, which is also known as koilonychia. There are a few reasons why you may have these inward curves in your nails, including having iron-deficiency anaemia (plus the opposite of iron-deficiency anaemia, called haemochromatosis, which is when you have too much iron in your system), Raynaud’s disease and lupus.

Nail ridges

Vertical ridges on your nails often become more prominent as you get older but are rarely anything to worry about. Sometimes, however, they can be a sign that you are lacking in iron, folic acid or protein. But if you have grooves that run horizontally across your nails, the effect is called Beau’s lines, and it may be caused by a previous illness or injury, chemotherapy or if you have Raynaud’s disease by previous exposure to very cold temperatures (the ridges will appear several months after exposure).

Loose nails

Injuries to nails can lead to them becoming loose and eventually falling off. But if you haven’t sustained an injury it’s possible that a loose nail could be caused by a fungal nail infection, nail psoriasis, poor circulation, an overactive thyroid or a serious condition called amyloidosis, which is the result of proteins building up in tissues and organs in your body.

White horizontal lines

If you have white lines that run in parallel across your nails, it may be a sign that you have low protein levels, possibly because you have liver disease. White spots or specks under the nails are less of a worry, with some nutrition experts believing they may be a sign of zinc deficiency.

For more information about nail problems, read our guide here.

Nutritional support for nail biters

If you’re trying to give up the habit of biting your nails, taking a good-quality multivitamin and mineral supplement may help keep your nails healthy as they grow back, since your nail beds need a constant supply of vitamins, minerals and other nutrients to make new nail cells.

Many nutritional practitioners also recommend omega-3 supplements – such as fish oils – to help strengthen weak, brittle nails. Studies suggest these may be helpful for reducing inflammation (vii), which can be caused by the damage nail biting can do to the nails and surrounding skin. The omega-3 fatty acids found in oily fish may also help if you bite your nails to help yourself cope with a low mood, since studies have found it may help relieve anxiety and depression (viii).

If you’re a vegetarian or vegan you can still benefit from an omega-3 supplement, thanks to the availability of products that contain the natural triglyceride (TG) form of omega-3, which is sourced from plant organisms called microalgae rather than fish oils.

Several B vitamins – including biotin, vitamin B12 and folic acid – are also thought to be important for nail health. Biotin, for instance, has been found to have a positive effect on brittle nails (ix), while deficiencies in vitamin B12 and folic acid may cause nail deformities and brittleness (x). Vitamin B6, meanwhile, is needed for the body’s production of neurotransmitters including serotonin and norepinephrine, which help regulate your mood (an imbalance of serotonin is thought to be involved in anxiety).

Taking a good-quality B complex supplement may also be helpful, since some B vitamins have been linked with obsessive-compulsive disorder (onychophagia is classed as a specified obsessive-compulsive and related disorder). Indeed, in one study, scientists suggest obsessive-compulsive disorder may be an early symptom of vitamin B12 deficiency (xi).

Several nutrients may also help if you bite your nails as a way of coping with stress and anxiety, including:

L-theanine   An amino acid found almost exclusively in green, black, oolong and pekoe tea, theanine is believed to stimulate the production of calming alpha brain waves (xii). There’s also evidence theanine may help reduce stress (xiii). Drinking green, black, oolong or pekoe tea can help increase your intake of theanine, or you could try a theanine supplement.
Lemon balm and valerian   Often recommended by herbal practitioners to help aid relaxation, some small-scale studies have found lemon balm may help reduce anxiety levels (xiv). Combining lemon balm with valerian – another herb often recommended by natural practitioners as a mild sedative – may also help you feel calm, say researchers (xv). Valerian is used for the temporary relief of mild anxiety as well as sleep disturbances, based on traditional use only.

Nail biting can be a difficult habit to break, but this guide should help to make it a little easier. For more information on a number of common health conditions, feel free to visit our health library.



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Disclaimer: The information presented by Nature's Best is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications.

Our Author - Christine Morgan


Christine Morgan has been a freelance health and wellbeing journalist for almost 20 years, having written for numerous publications including the Daily Mirror, S Magazine, Top Sante, Healthy, Woman & Home, Zest, Allergy, Healthy Times and Pregnancy & Birth; she has also edited several titles such as Women’ Health, Shine’s Real Health & Beauty and All About Health.

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