Why do we bite our nails?

It can ruin the appearance of your hands, could be unhygienic and can hurt if you take it too far. So why do people do it? Biter Tom Stafford investigates

What do ex-British prime minster Gordon Brown, Jackie Onassis, Britney Spears and I all have in common? We all are (or were) nail biters.

It’s not a habit I’m proud of. It’s pretty disgusting for other people to watch, ruins the appearance of my hands, is probably unhygienic and sometimes hurts if I take it too far. I’ve tried to quit many times, but have never managed to keep it up.

Lately I’ve been wondering what makes someone an inveterate nail-biter like me. Are we weaker willed? More neurotic? Hungrier? Perhaps, somewhere in the annals of psychological research there could be an answer to my question, and maybe even hints about how to cure myself of this unsavoury habit.

My first dip into the literature shows up the medical name for excessive nail biting: ‘onychophagia’. Psychiatrists classify it as an impulse control problem, alongside things like obsessive compulsive disorder. But this is for extreme cases, where psychiatric help is beneficial, as with other excessive grooming habits like skin picking or hair pulling. I’m not at that stage, falling instead among the majority of nail biters who carry on the habit without serious side effects. Up to 45% of teenagers bite their nails, for example; teenagers may be a handful but you wouldn’t argue that nearly half of them need medical intervention. I want to understand the ‘subclinical’ side of the phenomenon – nail biting that isn’t a major problem, but still enough of an issue for me to want to be rid of it.

It’s mother’s fault

Psychotherapists have had some theories about nail biting, of course. Sigmund Freud blamed it on arrested psycho-sexual development, at the oral stage (of course). Typical to Freudian theories, oral fixation is linked to myriad causes, such as under-feeding or over-feeding, breast-feeding too long, or problematic relationship with your mother. It also has a grab-bag of resulting symptoms: nail biting, of course, but also a sarcastic personality, smoking, alcoholism and love of oral sex. Other therapists have suggested nail-biting may be due to inward hostility – it is a form of self-mutilation after all – or nervous anxiety.

Like most psychodynamic theories these explanations could be true, but there’s no particular reason to believe they should be true. Most importantly for me, they don’t have any strong suggestions on how to cure myself of the habit. I’ve kind of missed the boat as far as extent of breast-feeding goes, and I bite my nails even when I’m at my most relaxed, so there doesn’t seem to be an easy fix there either. Needless to say, there’s no evidence that treatments based on these theories have any special success.

Unfortunately, after these speculations, the trail goes cold. A search of a scientific literature reveals only a handful of studies on treatment of nail-biting. One reports that any treatment which made people more aware of the habit seemed to help, but beyond that there is little evidence to report on the habit. Indeed, several of the few articles on nail-biting open by commenting on the surprising lack of literature on the topic.

Creature of habit

Given this lack of prior scientific treatment, I feel free to speculate for myself. So, here is my theory on why people bite their nails, and how to treat it.

Let’s call it the ‘anti-theory’ theory. I propose that there is no special cause of nail biting – not breastfeeding, chronic anxiety or a lack of motherly love. The advantage of this move is that we don’t need to find a particular connection between me, Gordon, Jackie and Britney. Rather, I suggest, nail biting is just the result of a number of factors which – due to random variation – combine in some people to create a bad habit.

First off, there is the fact that putting your fingers in your mouth is an easy thing to do. It is one of the basic functions for feeding and grooming, and so it is controlled by some pretty fundamental brain circuitry, meaning it can quickly develop into an automatic reaction. Added to this, there is a ‘tidying up’ element to nail biting – keeping them short – which means in the short term at least it can be pleasurable, even if the bigger picture is that you end up tearing your fingers to shreds. This reward element, combined with the ease with which the behaviour can be carried out, means that it is easy for a habit to develop; apart from touching yourself in the genitals it is hard to think of a more immediate way to give yourself a small moment of pleasure, and biting your nails has the advantage of being OK at school. Once established, the habit can become routine – there are many situations in everyone’s daily life where you have both your hands and your mouth available to use.

Understanding nail-biting as a habit has a bleak message for a cure, unfortunately, since we know how hard bad habits can be to break. Most people, at least once per day, will lose concentration on not biting their nails.

Nail-biting, in my view, isn’t some revealing personality characteristic, nor a maladaptive echo of some useful evolutionary behaviour. It is the product of the shape of our bodies, how hand-to-mouth behaviour is built into (and rewarded in) our brains and the psychology of habit.

And, yes, I did bite my nails while writing this column. Sometimes even a good theory doesn’t help.


This was my BBC Future column from last week

35 thoughts on “Why do we bite our nails?”

  1. Couldn’t agree more: habits have no other significance than their performance. More interesting would be to know how it is that the more revolting/unhygenic habits seem to override peoples’ appreciation of their fellows’ disgust.

  2. There may be a genetic and environmental influences involved in nail-biting, too. Often biting nails seems to “run in families,” which could be due to some common trait or social learning. Probably (as most things are) a combination of both. I think it is a compulsive behavior that falls on the OCD spectrum, although in many cases it is minor enough. I wonder if there are any similarities with excessive grooming in mice.

  3. I also wonder: both the fingers and the mouth have large cortical representation on the sensory homunculus. Is the combination involved in the habit of nailbiting not particularly potent because it forms such a BIG part of the sensory cortex compared to many other forms of compulsive activity? How many smokers bite their nails? How much different are these neural “circuitries”?

  4. Not using my real name for this… I’ve managed to give up nail-biting but I am an inveterate toe-picker / biter / chewer. It’s gross and embarrassing and so so so hard to give up (I’ve never succeeded. In fact I’ve gotten worse). It doesn’t help that the habit produces its own conditions of reproduction: a little bit of tough skin sticking out! Must pick! Your body’s attempts at recovery produce these rough nubbly little surfaces… My mom is a toe-picker and I’ve noticed my 3 year old starting to pick her toes. I’m horrified and transfixed and *can’t stop doing it in front of her*.

  5. If you want to know my “secret” for giving up nail biting: I chipped a front tooth (on the inside face, where it doesn’t show aesthetically) and since then have not been able to get a satisfying pincer bite for nail-nibbling. It still took a long time, I would try and would have this intense feeling of frustration when it didn’t “work”. But eventually the habit went away. Toes, though, are tougher flesh for picking at — you can get an approximate chomp, or use your fingers.

  6. As a child I bit my nails, very often causing damage of the sort that has you run to bathroom to run them under the coldest water possible, but quite apropos to the title of your article here, I stopped precisely because my father asked me one day, “Why do you bite your nails?”

    And I didn’t have an answer. And it stopped me in my tracks. Why did I do it? I didn’t have a reason.

    So I stopped.

    (I took up picking at hangnails instead 😉 )

  7. Great theory! The “deep rooted everything” trend is getting very old. As George Dvorsky said, drop the adaptive traits obsession, because really, life is a series of tradeoffs.

    As for habits: I like talking to myself. Works wonders. I’ve managed to quit smoking and get through races with this method. I stop what I’m doing and give myself a good lecture. People will stare at you but really, doesn’t that just make it more fun?

  8. um.er… let’s consider a simpler rationalization:

    Without access to nail clippers, having nails too long could be life threatening. They would break off and expose skinless open flesh. Humans learned to habitually bite their nails to prevent that from happening.

    If you don’t think that is logical, perhaps consider:Cultural reasons. Poor mates would have poor personal hygiene/habits. Short nails/hair is a good signal of a good mate.

  9. I agree with your theory. Shy does everything always have to be deeply rooted in some kind of childhood trauma/parental failure/sexual “deviance”?

    I nibble at hangnails/the skin around my nails, and sometimes I can’t stop ripping until they bleed. The habit seems to get worse when I have drier skin and more hangnails, so I prevent that by moisturizing regularly and snipping of any loose bits of skin with sharp nail scissors until there is nothing left to pick at. Also, wearing nail polish: I don’t want to damage it and/or ingest any.
    In a similar vein, I nibble at loose skin flakes on my lips and pick at bumps/zits on my upper arms and face whenever I discover any. Anything that sticks out, so to speak. Again, it gets worse when I have a lot of those, and prevention (lip balm/good skin care) seems to help. Even picking my nose (when no-one is watching…) gives me similar satisfaction (keep tissues at hand). So there does seem to be some kind of grooming connection.

    For nail biting, maybe cutting your nails very short and filing off any corners would help?

  10. After biting my nails all of my life (and quitting the habit not having crossed my mind) I suddenly stopped doing so around 18 months ago. I don’t recall at what point I stopped, and it certanly wasn’t a conscious decision by me. One day I realised my nails were getting unusually long and I was forced to trim them with clippers, a rare event. I haven’t bitten them since.

    I’ve been wracking my brains ever since trying to pinpoint what event – if any – might have lead me to cease, but I’m still drawing a blank.

    1. I’ve also suddenly stopped biting my nails after a lifetime of biting. I would love to know why as it wasn’t a conscious decision. My girlfriend was trying to convince me to stop…then we broke up. About a week later I noticed that my nails had grown. Going on 3 weeks now. I don’t have much of an urge to bite, but I do give them a bit of a nibble now and then. So weird…I assume my break up somehow had a subconscious affect on my nail biting.

  11. I think I agree with the therapists who suggest that “nail-biting may be due to inward hostility”.

    You go on later to say:

    “…there is a ‘tidying up’ element to nail biting – keeping them short – which means in the short term at least it can be pleasurable, even if the bigger picture is that you end up tearing your fingers to shreds.”

    When you tidy your nails up, its to make them look better – perfecting them, if you will. You’re making your nails, hence yourself, more perfect. I’d argue low self-esteem… which I guess is code for ‘deep-rooted issues’. Sorry.

    That said, at least I’m not the only adult that bites their nails. 🙂

  12. ..as a nail biter {blushes}, I could’ve sworn I had meself justified that it was a habit formed in facilitation of thinking; much like pacing ala Holmes conversing with Dr. Watson, or chewing gum ..at times I think the act of oral manual digestion imitates and aids the pace of which memory retention is best absorbed, “digested”. Any nail biter would have you know there’s just an unexplainable technicality to the habit that instinctually, we already know that it certainly hasn’t got anything to do with hunger why we do it.

    ENTER, the nutritionist p.o.v.:

    At some point of being such an expert with palatal-dental manicure, I considered that I may actually be lacking in certain nutrients and am perhaps making up for the lack of ..say, silica and certain B-complexes by forming a self-sustaining habit of consuming it through the closest available 24/7 mean possible? A deficiency in all sorts of B complexes does take a toll on the body, one of which seems to have lend a hand in developing depression so symptoms anxiety shouldn’t be that far off, I reckon..

    ..I stayed with this nutritional deficient theory of mine due to the success rate at which I’d actually quit nail-biting after 3 weeks onwards with daily intake of horsetail [silica] supplements, I honestly stayed with this understanding ..UNTIL, well, I noticed I had quit to bite on my nails but began biting the callouses or skin bits on the side of my nails, at times til I bled!

    {hands on hips} mmph.

    Also, I don’t see myself nibbling on hair which also has silica so the compulsion has been a bit of a mind-boggler [..I have been biting as I was writing this, by the very way].

    For the time being, the only advantageous side-effect of my nail-biting is that I seem to have developed a much higher rate of nail regeneration compared to most over the years of constant nibbling on them fingernails – it’s not really a plus but I could see mysel in the Book of Records someplace for fastest growing fingernails.

  13. There are certain nail polishes for nail biters. It tastes horrible. When I was a kid I bit my nails so my mom bought it for me. I’ve never done it since. It’s bitter and disgusting. It is for this very problem. It doesn’t matter why you bite your nails but there are products out there to stop it. It’s pretty simple. Take away the pleasure and it stops. Simply paint your nails with the stuff (it’s clear so men can use it too) until you don’t have the automatic reaction to bite.

  14. Also, Tom: Might you’ve any good reads on the compulsions of nail-biting being related to spiritual problems, by any chance?

    I wonder if anyone studying cognitive sciences had explored with interesting results on the relation of these compulsions to presumably spiritually-based issues – would definitely like to hear your perspective on the parallels of psychological issues vs spiritual problems with regards to compulsions and compulsiveness.

  15. I only started biting my nails half-way through elementary school. It was a bad habit, then. They got ugly-short, but never to the point of ‘injury’. Taping my fingers (a cold turkey solution) helped reduce the impulse over the time that I taped them, if it was long enough.

    Eventually, the problem just transformed into a regular grooming habit. Every now and then I look at my nails, and if they look like they’re getting too long, or are irregularly shaped, I slightly go at them with my teeth to either cut or file. I haven’t used a nail-file since my nail-biting problem began. But I almost never bite them down now to less than a milimeter of white.

    1. Also, now that I think about it, my impulse is relegated to soft nail biting without biting off, on the occasions when I do not intend to shorten them.

  16. When I was a child with a nail-biting habit, I noticed that my aunt and grandmother, who did the same, had awful-looking hands because of it. I decided to stop. My method was to chew gum instead. It was totally efficient; I easily stopped the nail-biting habit.

    I’m not sure when exactly I stopped chewing gum; that habit kind of withered away by itself.

    But I do still have an “oral fixation”; I’m a stress-eater and overweight.

    Good luck curing your habit.

  17. When I was young, I used to bite my nails all the way down to the bed, until they hurt so much I had to bandage them so I wouldn’t mess with them. Only once did I ever make myself bleed, though.

    A few years ago, I decided I wanted to quit. I tried dipping my fingers in nail polish remover but the taste wore off too quickly for me to keep up with it. Now I find that as long as I keep my nails clipped short and I rub lotion into my cuticles, I don’t feel the need to bite them. Putting nail polish on can help too, for some reason. It’s when they start to grow out that I start obsessing over them.

  18. I think nail biting is triggered by a stressful situation that we don’t feel we have control over. The nail biting allows the person to feel in control and as if they’re making progress (despite doing damage to their nails and cuticles).

    This is why we bite our nails unconsciously. The trigger coems from a feeling which prompts us to distract ourselves with an act that we feel in control of.

  19. I found hypnosis helped me stop biting my nails ( a few times) but it’s not permanent. Stress seemed to undo the hypnosis.

  20. I was a lifelong nail-biter. At 36yrs I started learning guitar for the first time (steel-string) and I’ve not bitten my nails since – not even once, and no relapses after a year now. I guess whatever nervous energy I have is working itself out on the guitar.

  21. Some good comments here. The “control” theory above works for me. I had hoped Invisiline braces (plastic teeth covers) might squelch my habit. No such luck, though I have moved to mostly chomping them with nail clippers.

  22. Biting nails might be an attempt to ease the subtle uncomfortable feeling of the stretched skin that is attached to the ever growing nail. This is the reason why people might switch to pulling or biting the cuticles off. There are also nervous knots on both sides of a finger, where the nail connects to skin. Massaging that spot may take away the desire to bite nails or cuticles off. Separating the dead cuticle to that point might work to the same effect. May be not everyone has this physiology thus not all people have the desire to bite their nails.

  23. I used to suck my thumb during sleep and later on bite my nails. I used tape while sleeping to stop the sucking and later on relised how ugly the bit nails looked like. It also helped that at some point wanted to learn guitar and i consiously had to stop bitting my long nails. Now that i dont play anymore i occasionly bite them without cutting bits, just for the pleasure of it. But helps that everytime i feel like bitting them (cause are getting long) i use a nail clipper to shorten them and the impulse goes away.

  24. When I was five years old, I saw some dark lint in the deep corners of my little fingernails. I couldn’t get at them by picking so I chewed through my skin. I’d get the lint out as a reward. Then it became a habit.

    Actually, it’s more than just a habit, it’s my happy place. When I watch TV or concentrate at work, I do it without even noticing.

    It’s routine: A week would go by with light chewing and I’d notice my nails are too long. Then I’d “gorge” and trim them all too much. Then I’d feel regret for days until I forget. Then they grow back a bit too much and it restarts.

    If I were good, I’d be able to go a couple of weeks without biting them, but the temptation of biting full formed nails would become too much.

  25. I can recall the exact circumstances of my taking up this life long habit. I was about seven years old and had been playing in the dirt. The sensation of dirt packed tightly under my fingernails drove me crazy. I tried scraping it out with my teeth but couldn’t relieve the feeling. When my teeth caught a small split in one nail I bit and peeled the nail off. Instant relief! I immediately moved on to my other fingers. As I worked my way through them I even thought “This is how people start biting their nails.” I kid you not. I suspect it was the sensation of the remaining rough edges that kept me making ‘adjustments’ until the habit was fully ingrained, but I really have no idea why I’ve kept it up. Perhaps I’m a little OCD. If so, I’m happy this is it’s only manifestation!

  26. I have a question:

    Before nail clippers, before miniature scissors, how did one trim ones nails?

    Don’t apes band gorillas bite their nails. Contrary to much of the discussion on this site, I think it’s normal.

  27. Ultimately, anything we do is about gaining comfort. Even those things we do to hurt ourselves is ultimately about some notion of comfort. Thus, for those who bite their nails, there is some comfort in doing so. As long as that comfort outweighs the discomfort of being a nail-biter, the habit will likely continue.

  28. Nail biting is an ugly habit with a negative social stigma but a common way for mega numbers of people around the globe to deal with stress. Compulsive nail biters have existed throughout human history in all strata of society. No doubt it can in some cases result in dental and mouth problems, minor infections and sickness if one’s immune system is compromised. But if the immune system of a non nail biter is not working, he is just as vulnerable to the same pathogens. Since humans are exposed to billions of pathogens all the time, it is irrational to argue the nail biter faces more health risks than the average individual who doesn’t bite his nails. It is poor sanitation in general or lack of medicinal remedies that pose risks to health in the general population. How can nail biting be stigmatized as a dirty activity posing any greater health risks than sexual activity between people where there is intimate contact and the interchange of body fluids? It is because sex is vital for the survival of our species and nail biting deemed aberrant behavior.

    I have been a chronic nail biter for about 35 years. As a kid I played in dirt, was close to dogs and animals, fished with worms and frequently had dirty hands that ended up in my mouth. I never contracted pin worms or had more sickness than playmates who did not bite their nails. A non nail biter could just as easily ingest microorganisms or worms though skin exposure or dirt collected beneath unbitten fingernails. It is exposure to pathogens in general, not the incidental habit of nail biting, that’s the culprit. The same applies to emotional issues. Nail biting can no doubt result from emotional issues and depression. Biting nails plays an incidental role as a coping mechanism but is not the cause of one’s problems or loss of self-esteem, though it seems logical that having painful and severely bitten nails could aggravate one’s depression in some circumstances.

    For whatever reason, I became a nail biter at a very early age and the habit persisted to the present. I never could overcome the urge and seemed programmed to bite my nails when certain stimuli occur. My nails are stubby and unattractive and I admit to biting them frequently in public. . . which I’m not ashamed about though aware some people find it offensive. I feel better when I bite my nails. If I try to stop, I feel self-conscious and repressed. I don’t know what prompted the habit since my family life was relatively normal and I was a happy, active kid. For whatever reason, unlucky natural selection made me a chronic nail biter. There are others just like me everywhere.

  29. I agree, wholeheartedly. This article’s truth is harmonic with my own experience. I feel not-quite validated, but will most probably keep intermittently biting my nails like I have. I am not more justified, yet I do have kinship.

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