Nail biting is so common that it's barely commented on. Hair pulling is less visible but more alarming when parents notice it. Skin picking tends to be hidden and is often accompanied by significant shame. All three are variants of the same category – body-focused repetitive behaviours, or BFRBs – and all three are substantially underrecognised as conditions that respond to specific treatment.
The mistake most parents make when they notice these behaviours is trying to stop them through attention, reminders, or willpower alone. This approach usually doesn't work, and often makes things worse, partly because the behaviour is more automatic than it appears, and partly because bringing more attention to something the child is already aware of and often ashamed of increases distress without reducing the behaviour.
Healthbooq (healthbooq.com/apps/healthbooq-kids) covers children's emotional health and behaviour.
What BFRBs Are
Body-focused repetitive behaviours are repetitive, self-directed actions involving the body that cause some degree of physical damage or cosmetic change and are experienced as difficult to control. The main ones are:
Trichotillomania (hair pulling): compulsive pulling of hair from the scalp, eyebrows, eyelashes, or other body areas. In its clinical form, it causes visible hair loss and significant distress. It is estimated to affect around 1-2% of the population at some point, with onset often in childhood or early adolescence.
Excoriation disorder (skin picking): repetitive picking at skin, spots, scabs, or imperfections, often to the point of sores, scarring, or infection. It is more common than trichotillomania and affects an estimated 1.4-5% of the population in its clinical form.
Onychophagia (nail biting): biting nails, cuticles, and surrounding skin. Subclinical nail biting affects around 20-30% of children; clinical nail biting severe enough to cause tissue damage or significant distress affects a smaller proportion.
Other: lip and cheek biting, nose picking to excess, and several other variants fall within the same framework.
The TLC Foundation for Body-Focused Repetitive Behaviors, founded by Suzanne Mouton-Odum and based in the US, has been central to raising awareness and developing treatment resources for these conditions internationally.
The Psychology Behind Them
BFRBs are not primarily driven by anxiety, though anxiety and stress are among the triggers. Research by Douglas Woods and Michael Twohig (central figures in BFRB research; Woods at Marquette University) established that BFRBs have a functional dimension: they occur most often during states of high-focus (studying, watching television, being online) or boredom rather than exclusively in anxious states. The behaviour appears to serve a regulatory function – not necessarily anxiety reduction, but something like sensory stimulation or a way of occupying the hands during cognitive load.
This explains why telling a child to simply stop is ineffective: the behaviour is often semi-automatic (occurring without conscious awareness) and serves a functional need. Once the awareness is there – once the child notices they're doing it – they've often been doing it for several minutes already.
Neurobiologically, BFRBs are classified in DSM-5 and ICD-11 alongside OCD in the "obsessive-compulsive and related disorders" category, reflecting shared features: the repetitive, compulsive nature, the difficulty stopping, and some overlap in neural circuitry (involving the basal ganglia and reward pathways). They are, however, distinct from OCD: BFRBs are often associated with positive or neutral affect during the behaviour (sometimes described as a satisfying or soothing quality) rather than the anxiety relief typical of OCD compulsions.
Habit Reversal Training
The most evidence-based treatment for BFRBs is habit reversal training (HRT), a behavioural therapy developed by Nathan Azrin and R. Gregory Nunn in the 1970s and refined by subsequent researchers including Michael Twohig and Douglas Woods. The Comprehensive Behavioural Treatment (ComB) model, developed by Penzel and refined by Woods and colleagues, extends HRT for more complex presentations.
HRT has two main components:
Awareness training: Helping the individual recognise when and in what context the behaviour occurs – the specific triggers (situations, emotional states, sensory contexts), the warning signals just before the behaviour, and the characteristic situations (sitting at a desk, watching television, being in a car). Many people are surprised by the pattern once they map it; the behaviour is more situationally specific than it feels.
Competing response: Developing an alternative behaviour that is physically incompatible with the BFRB and that can be performed in the same contexts without drawing attention. For hair pulling, this might be clenching the fist or placing the hand flat on the leg. For skin picking, wearing textured rings or placing hands on a smooth stone. For nail biting, wearing flavoured nail varnish or using a fidget tool. The competing response needs to feel similar to the BFRB in terms of sensory engagement, which is why generic alternatives ("put your hands in your pockets") often don't work.
Multiple randomised controlled trials have demonstrated the efficacy of HRT and ComB for trichotillomania and excoriation disorder in both children and adults. Response to treatment is reasonably good for those who can engage with the training.
What Parents Can Do
Reducing shame and increasing awareness is the starting point. A parent who notices the behaviour and says "I've noticed you're pulling your hair – I want you to know that some people do this and there's a therapy that can help, and I'd like to talk to you about it when you're ready" creates a different dynamic from one who slaps the hand away, nags, or makes it a source of ongoing family conflict.
Pointing out the behaviour in real-time is useful in the context of HRT – it helps build awareness. Outside that context, it tends to increase self-consciousness and shame without helping.
For younger children, BFRBs that are mild and not causing significant physical damage or distress often remit spontaneously without treatment, particularly if they started during a period of stress that has resolved.
For children whose behaviour is causing physical damage (bald patches, wounds, infections), significant distress, or social difficulty (hiding their hands, wearing gloves to cover damage), referral to a clinical psychologist or therapist trained in HRT or ComB is the appropriate next step. CAMHS can make this referral; in practice, wait times are long, and private psychology with a BFRB-trained therapist is often more accessible.
The TLC Foundation for Body-Focused Repetitive Behaviors provides a therapist directory, self-help resources, and peer support for those affected internationally.
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.
