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Seven-year-old Flora and her twin sister Iris are brought to see you by their exasperated maternal grandmother Mary.

They have headlice for the third time this school year, and Mary is fed up with wet combing.  The twins live with her permanently after their parents went to prison 18 months ago for drug-related offences, and Mary is frustrated and ashamed that they seem so often to pick up headlice.

She already feels judged at the school gate and is now upset that an invitation to a sleepover was refused, as other parents are complaining the twins always have nits.

Headlice are a common minor ailment. A systematic review in 2020 aiming to determine the worldwide prevalence of head lice in school children [Hatam-Nahavandi, 2020] found a total prevalence of 19%, with male children half as likely as females to have an infestation. 

Risk factors include age (3-12 years), sex (female) and ethnicity (any other than black) [NICE CKS]. The average infestation consists of 30 live lice, though between 10 and 1000 are typically found.

The life cycle of the head louse involves three stages: egg (or ova), nymph, and adult.

Headlice and nits

The eggs are oval-shaped, translucent, and may be confused with dandruff. They are laid close to the scalp surface by adult lice and are strongly attached to the hair with a glue-like substance. They usually take about 7–10 days to hatch. The term ‘nits’ is often used to describe louse eggs; however, technically “nits” are the empty shells of hatched eggs that turn white and remain attached to the hair but further from the scalp surface.

Nymphs are baby lice that hatch from the eggs. They are about the size of a pinhead, pearly white and take about 7–10 days to mature into adult lice.

Adult head lice are up to 3 mm long. Tan or grey and have six legs ending in hook-like claws to hold onto the hair. The female louse lays anywhere from 50–150 eggs during her 30–40-day lifespan.

How do we diagnose headlice?

Headlice are usually transmitted from head to head. The lice crawl but cannot jump or fly. Once detached from a human head, they will only live 24-48 hours but can be spread by sharing hairbrushes or combs.

The commonest symptom of headlice is an itchy scalp. To diagnose an active infestation, at least one live louse should be detected (using wet combing with a special fine-toothed detection comb).  NICE clearly states that “the presence of louse eggs alone, whether hatched (nits) or unhatched, is not proof of active infestation.

How do we treat headlice?

UK guidance from NICE CKS and the British Association of Dermatologists (BAD) recommends head lice should be treated with one of the following:

  • A biological insecticide, such as dimethicone 4% lotion (Hedrin®). Physical insecticides work by physically coating the surfaces of head lice and suffocating them. This means resistance is unlikely to develop.
  • A chemical insecticide, such as malathion 0.5% aqueous liquid (Derbac-M®). Resistance is known to develop quickly to chemical insecticides, which will reduce efficacy.
  • Wet combing with a fine-toothed head louse comb (such as the Bug Buster® comb, specifically named by NICE/BAD as the most effective product for use in this way). BAD recommends using conditioner or a dimethicone product to lubricate the hair, making the procedure easier, particularly for children with curly hair. BAD advises that the comb be immediately cleaned after each pass to remove lice and eggs by wiping on clean white paper or cloth. They signpost patients to the Community Hygiene Concern website for further information.

What about wet combing?

Advantages of wet combing

  • Contact with a clinician is not necessary.
  • No insecticides are used, so resistance is not an issue. 
  • No contraindications or precautions for its use. 
  • The method is inexpensive, and the kits are reusable. 
  • Clinical trials report cure rates of 38% and 52% at 14/15 days [Roberts et al., 2000; Hill et al., 2005].


  • The technique is time-consuming and labour-intensive; this may be a drawback when treating young children or if several people are to be treated simultaneously.
  • The method is ineffective if an unsuitable comb or incorrect method is used.
  • Cure rates are lower than other methods.

All household members should be checked for headlice, and if any live lice are detected, they should all begin treatment on the same day. All close contacts (e.g. classmates and friends) should be checked too. The combs and brushes of an infested person should be washed in hot water daily. Children need not be excluded from school or childcare settings when they have headlice.  After treatment, parents should check their child’s hair by wet combing at least weekly for a month to ensure the infestation has cleared. Head lice are extremely common, and it can take time to completely treat the infestation, particularly if more than one family member is infested.

You address Mary’s worries about being judged at the school gate and reassure her that social services are unlikely to be interested in the situation.

You tell her that the infestation does not necessarily indicate poor parenting or poor hygiene though you recognise why she is so worried. 

You recommend over-the-counter treatment and an intensive course of “bug busting” and suggest the girls wear their hair tied back at school or for other social activities. You give her the patient leaflet from, and she and the twins leave your clinic reassured.

Complications from headlice are rare. Rarely an untreated infestation can cause severe itching, scalp dermatitis and secondary bacterial infection. Although common in all social demographics, a prolonged and persistent failure by the child’s parents or carers to treat the infestation is likely distressing for the child and could also indicate other welfare issues.  Professionals should know that a ‘Severe and Persistent Infestation’ of head lice or ‘nits’ (NICE, 2016) may indicate serious welfare concerns for children and young people. This has been evidenced in serious case reviews.


Hatam-Nahavandi, K., Ahmadpour, E., Pashazadeh, F., et al. (2020) Pediculosis capitis among school-age students worldwide as an emerging public health concern: a systematic review and meta-analysis of past five decades. Parasitology Research 119(10), 3125-3143.

Hill, N., Moor, G., Cameron, M.M., et al. (2005) Single-blind, randomised, comparative study of the Bug Buster kit and over-the-counter pediculicide treatments against head lice in the United Kingdom. British Medical Journal 331(7513), 384-387!topicsummary

NICE Guideline NG76 Child abuse and neglect: recognising, assessing and responding to abuse and neglect of children and young people

Roberts, R.J., Casey, D., Morgan, D.A. and Petrovic, M. (2000) Comparison of wet combing with malathion for treatment of head lice in the UK: a pragmatic randomised controlled trial. Lancet 356(9229), 540-544. 


  • Dr Tara George. MBChB (Hons) Sheffield 2002, FRCGP, DCH, DRCOG, DFSRH, PGCertMedEd Salaried GP and GP Trainer, Wingerworth Surgery, Wingerworth, Derbyshire. GP Training Programme Director, Chesterfield and the Derbyshire Dales GP Speciality Training Programme. Out of Hours GP and supervisor, Derbyshire Health United. Early Years Tutor, Phase 1, Sheffield University Medical School. Mentor, GP-s peer mentoring service and Derbyshire GPTF new to practice scheme. External Advisor RCGP. Host Bedside Reading podcast. Pronouns: she/her When she's not doing doctory things Tara loves to bake, to read novels, run and take out some of that pent up angst in Rockbox classes.

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