Nail biting is so common we barely notice it. Hair pulling is less visible and tends to alarm parents the moment they spot a thin patch on the scalp. Skin picking is usually hidden, often under sleeves or makeup, and almost always carries a heavy load of shame. All three belong to the same family of conditions — body-focused repetitive behaviours, or BFRBs — and all three are far more responsive to specific treatment than most parents (and many GPs) realise.
The mistake most parents make on noticing these behaviours is trying to stop them with reminders, hand-slapping, or willpower talks. It rarely works, and often makes things worse. The behaviour is much more automatic than it looks from the outside, and shining attention on something the child is already aware of and ashamed of mostly just adds to the distress.
Healthbooq (healthbooq.com/apps/healthbooq-kids) covers children's emotional health and behaviour.
For more, see our complete guide to emotional development.
What BFRBs Are
BFRBs are repetitive, self-directed behaviours involving the body that cause some degree of physical damage or cosmetic change and are experienced as hard to stop. The main four:
Trichotillomania (hair pulling): compulsive pulling of hair from the scalp, eyebrows, eyelashes, or elsewhere, to the point of visible hair loss. Estimated to affect around 1–2% of people at some point in their lives, with onset most often in childhood or early adolescence.
Excoriation disorder (skin picking): repetitive picking at skin, spots, scabs, or perceived imperfections, often producing sores, scarring, or infection. More common than trichotillomania — around 1.4–5% of the population in its clinical form.
Onychophagia (nail biting): biting the nails, cuticles, and surrounding skin. Mild nail biting affects around 20–30% of children at some point. Severe nail biting that causes tissue damage or significant distress is much less common but still affects a meaningful minority.
Other variants: lip and cheek biting, severe nose picking, and a few others fit within the same framework and respond to the same treatments.
The TLC Foundation for Body-Focused Repetitive Behaviors has been central in raising awareness of these conditions and building treatment resources for clinicians and families internationally.
The Psychology Behind Them
A common assumption — that BFRBs are caused by anxiety — is only partly right. Anxiety and stress are among the triggers, but Douglas Woods (Marquette University) and Michael Twohig's research established that BFRBs occur most often during states of high focus (studying, watching TV, scrolling on a phone) or boredom, not exclusively in anxious states. The behaviour seems to serve a regulatory function — sensory stimulation, a way of occupying the hands during cognitive load — rather than purely reducing anxiety.
This explains why "just stop" doesn't work. The behaviour is often semi-automatic; by the time the person notices they're doing it, they've usually been at it for several minutes. The hand has a kind of muscle memory that operates beneath awareness.
Neurobiologically, BFRBs are classified in DSM-5 and ICD-11 alongside OCD in the "obsessive-compulsive and related disorders" category, reflecting overlap in the basal ganglia and reward pathways. But they're distinct from OCD: BFRBs are often associated with a positive or neutral feeling during the behaviour — sometimes described as soothing or satisfying — rather than the anxiety relief that drives OCD compulsions.
Habit Reversal Training
The best-evidenced treatment is habit reversal training (HRT), a behavioural therapy developed by Nathan Azrin and R. Gregory Nunn in the 1970s and refined since by Michael Twohig, Douglas Woods, and others. The Comprehensive Behavioural Treatment (ComB) model, developed by Charles Mansueto and refined by Woods and colleagues, extends HRT for more complex presentations.
HRT has two main parts:
Awareness training. The child (with help) maps out exactly when and where the behaviour happens — the specific situations (sitting at a desk, watching TV, lying in bed), the emotional or sensory states that precede it, and the small physical signals that come just before (the hand drifting up, fingers tensing). Most people are surprised by how patterned the behaviour is once they look. It's much more situationally specific than it feels from inside.
Competing response. An alternative behaviour, physically incompatible with the BFRB, that can be done quietly in the same situations. For hair pulling, that might be making a fist or placing the hand flat on the leg. For skin picking, holding a textured ring or a smooth stone. For nail biting, a fidget tool or a strong-tasting nail varnish. The competing response needs to engage the same kind of sensory need — generic advice like "put your hands in your pockets" rarely works because it doesn't satisfy what the BFRB was satisfying.
Multiple randomised controlled trials show HRT and ComB are effective for trichotillomania and excoriation disorder in both children and adults. Response is reasonably good for those who can engage with the work — though it requires practice and the willingness to pay sustained attention to a behaviour the person has often spent years avoiding looking at.
What Parents Can Do
Start by reducing shame. A parent who says "I've noticed you're pulling your hair — I want you to know lots of people do this, there's a therapy that helps, and we can talk about it whenever you're ready" creates a different family climate than one who slaps the hand away or makes the behaviour a recurring source of conflict.
Pointing out the behaviour in real time is useful within the structure of HRT — that's how awareness gets built. Outside that context, real-time reminders mostly increase self-consciousness and shame without reducing the behaviour. So unless you're working through HRT exercises together with a clinician's guidance, try to leave the in-the-moment commentary alone.
For younger children, mild BFRBs that aren't causing significant damage or distress often fade on their own, particularly when they started during a period of stress that has since passed.
For children whose behaviour is causing visible damage (bald patches, wounds, infections), real distress, or social hiding (long sleeves in summer, hats indoors, avoiding swimming or PE), refer on. CAMHS can make the referral to a clinical psychologist trained in HRT or ComB; in practice, NHS waits are often long, and self-funded private psychology with a BFRB-trained therapist tends to be faster.
The TLC Foundation for Body-Focused Repetitive Behaviors (bfrb.org) maintains a therapist directory, self-help resources, and peer support networks.
Key Takeaways
Body-focused repetitive behaviours (BFRBs) – including nail biting, hair pulling (trichotillomania), skin picking (excoriation disorder), and cheek biting – are common in children and teenagers, affecting an estimated 2-5% of the population to a clinically significant degree and many more at a subclinical level. They are not simply bad habits: they are associated with emotional regulation, occur often during periods of boredom or focus rather than only anxiety, and have a neurobiological basis. Habit reversal training (HRT) – a behavioural therapy that involves awareness training and competing response development – is the best-evidenced treatment. Social stigma and shame are significant barriers to help-seeking.
