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Child health Infections and infestations Skin and nail

Head lice

Last revised in May 2026

Head lice (Pediculus humanus capitis) are parasitic insects that infest the hairs of the human head and feed on blood from the scalp.

Head lice: Summary

  • Head lice (Pediculus humanus capitis) are wingless parasitic insects that infest the hairs of the human head and feed on blood from the scalp. Head lice infestation is known as pediculosis capitis.
    • An infestation usually involves fewer than 10 live lice. 
    • If left untreated, head lice infestation may persist for long periods.
  • Detection combing is the best way to confirm the presence of lice. This is the systematic combing of wet or dry hair using a fine-toothed (0.2–0.3 mm apart) head lice detection comb.
  • A diagnosis of active head lice infestation should only be made if a live head louse is found.
    • An itching scalp is not sufficient to diagnose active infestation.
    • The presence of louse eggs alone, whether hatched (nits) or unhatched, is not proof of active infestation.
  • A person should only be treated if a live head louse is found. All affected household members should also be treated on the same day.
  • Depending on the preference of the person and/or their parents/carers, their treatment history, the presence of any contraindications, and the cost of treatment, head lice can be treated with one of the following:
    • A physical insecticide, such as dimeticone 4% lotion (Hedrin®).
    • A traditional insecticide, such as malathion 0.5% aqueous liquid (Derbac-M®). 
    • Wet combing with a fine-toothed head louse comb (such as the Bug Buster® comb).
  • No treatment can guarantee success, but a treatment has the best chance of success if it is performed correctly and if all affected household members are treated on the same day. 
  • Detection combing should be done after all treatments to confirm the success of the treatment. If treatment is unsuccessful (that is, a live louse is found after treatment):
    • It should be confirmed that the treatment was used correctly.
    • Household members, close family, and close friends (both adults and children) should be assessed to identify possible sources of reinfestation.
    • The same treatment should be repeated, or a different treatment tried. If malathion was used, the possibility of resistance should be considered.
  • People should be advised that:
    • Children who are being treated for head lice can still attend school.
    • There is no evidence that head lice have a preference for either clean or dirty hair.
    • There is no need to treat (wash at high temperature or fumigate) clothing or bedding that has been in contact with lice, as the lifespan of a head louse is very short (1–2 days) once it is detached from a human head.
    • Essential oil-based treatments and herbal treatments are not recommended due to the lack of good-quality evidence on their safety and efficacy.
    • It is not possible to prevent head lice infestation. Children of primary school age should be examined regularly at home (using a detection comb) to identify infestation early.

Have I got the right topic?

From age 1 month onwards.

This CKS topic covers the management of head lice.

There are separate CKS topics on Pubic lice and Scabies.

The target audience for this CKS topic is healthcare professionals working within the NHS in the UK, and providing first contact or primary healthcare.

How up-to-date is this topic?

Changes

May 2026 — reviewed. A literature search was conducted in May 2026 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of this topic. No major changes to the recommendations have been made.

Previous changes

November 2021 — reviewed. A literature search was conducted in October 2021 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of this topic. No major changes to the recommendations have been made.

December 2016 — reviewed. A literature search was conducted in November 2016 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of this topic. No major changes to the recommendations have been made.

September 2015 — reviewed. A literature search was conducted in August 2015 to identify evidence-based guidelines, UK policy, systematic reviews, and key randomized controlled trials published since the last revision of this topic. No major changes to the recommendations have been made; however, the topic has undergone minor restructuring.

February 2015 — minor update. Hair loss has been reported as a very rare adverse effect of Hedrin® (dimeticone 4%).

March 2014 — minor update. Minor rewording of several sections to clarify the difference between nits (empty shells of hatched eggs) and live louse eggs. Additional information nodes in Background Information have been changed to main nodes to improve the flow of the topic.

May 2013 — minor update. The text regarding Lyclear SprayAway® has been changed or deleted as this product has been discontinued. The prescription for this product has also been removed.

January 2013 — minor update. Reference to a published paper inserted regarding the mode of action of Full Marks Solution®. This replaces a personal communication reference.

March 2011 — minor update. NYDA® (dimeticone 92% is now prescribable on the NHS). Issued in June 2011.

February 2011 — minor update. Advice from the manufacturer that isopropyl myristate and cyclomethicone solution (Full Marks Solution®) works by removing the wax coating on the louse exoskeleton, leading to uncontrollable dehydration and subsequent death has been added to the topic . Issued in February 2011.

December 2010 — minor update. Further detail added to the Basis for recommendation section of the Treatment recommendations to clarify why Hedrin® lotion is the only formulation of Hedrin® offered in this CKS topic. Issued in December 2010.

April 2010 — minor update. Minor rewording of several sections. Issued in April 2010.

November 2009 to March 2010 — topic revised. The evidence-base has been reviewed in detail, and recommendations are clearly justified and transparently linked to the supporting evidence. Changes to recommendations include:

  • Isopropyl myristate and cyclomethicone (Full Marks Solution®) and coconut, anise, and ylang ylang spray (Lyclear SprayAway®) are now recommended as treatment options.
  • Phenothrin and carbaryl are no longer recommended because they are no longer marketed in the UK.

December 2008 — minor update. The topic now includes the advice that people using dimeticone (Hedrin®) should avoid naked flames, cigarettes, and other sources of ignition while treatment is underway updated following a Medicines & Healthcare products Regulatory Agency (MHRA) Drug Safety Update. Issued in January 2009.

November 2007 — minor update to text. Malathion is now licensed for a second application after 7 days. The recommendation for a second application of insecticide 7 days after the first is unlicensed for phenothrin, permethrin, and carbaryl, and is different to the information supplied by the manufacturers: their package inserts state that a single application is sufficient. Issued in December 2007.

July 2007 — minor update to text of instructions for wet combing for the treatment of head lice. Issued in August 2007.

January to April 2007 — converted from CKS guidance to CKS topic structure. The evidence base has been reviewed in detail, and recommendations are more clearly justified and transparently linked to the supporting evidence.

August 2003 — reviewed. Validated in December 2003 and issued in February 2004.

November 2000 — rewritten. Validated in March 2001 and issued in June 2001.

Update

New evidence

Evidence-based guidelines

No new evidence-based guidelines since 1 May 2026.

HTAs (Health Technology Assessments)

No new HTAs since 1 May 2026.

Economic Appraisals

No new economic appraisals relevant to England since 1 May 2026.

Systematic reviews and meta-analyses

No new systematic reviews or meta-analysis which reach the CKS threshold for inclusion since 1 May 2026.

Primary evidence

No new primary evidence which reaches the CKS threshold for inclusion published since 1 May 2026.

New policies

No new national policies or guidelines since 1 May 2026.

New safety alerts

No new safety alerts since 1 May 2026

Changes in product availability

No changes in product availability since 1 May 2026.

Goals and outcome measures

Goals

To support primary healthcare professionals to provide advice on:

  • Eradicating live head lice and viable eggs.
  • Preventing transmission of head lice.

Outcome measures

No outcome measures were found during the review of this topic.

Audit criteria

No audit criteria were found during the review of this topic.

QOF indicators

No QOF indicators were found during the review of this topic.

QIPP - Options for local implementation

No QIPP - Options for local implementation were found during the review of this topic.

NICE quality standards

No NICE quality standards were found during the review of this topic.

Background information

What is it?

  • Head lice (Pediculus humanus capitis) are wingless parasitic blood-sucking insects around 2–3 mm long that infest the human scalp.
  • They live close to the scalp surface and feed by injecting small amounts of saliva into the scalp, allowing them to suck tiny amounts of blood every few hours.
  • An infestation usually involves fewer than 10 live lice.
  • Head lice infestation is known as pediculosis capitis.

[Nolt, 2022; Cummings, 2025]

What is the life cycle of the head louse?

  • The life cycle of the head louse involves three stages: egg (or ova), nymph, and adult.
    • Louse eggs (ova) are laid close to the scalp surface and are strongly attached to the hair with a glue-like substance. They are oval shaped, translucent, may be confused with dandruff, and usually take about 7–12 days to hatch (depending on the ambient temperature). 
      • The term 'nits' is often used to describe louse eggs; however, nits are technically the empty shells of hatched louse 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 look like the adults but are smaller in size. They take about 9–12 days to mature into adult lice. 
    • Adult head lice are about the length of a sesame seed (up to 3 mm long). They are tan to greyish white in colour and have six legs ending in hook-like claws to hold onto the hair. The female louse can live for 3–4 weeks and lay up to 10 eggs per day.  

[Leung, 2021; Nolt, 2022; Cummings, 2025]

How are head lice transmitted?

  • Transmission of head lice requires head-to-head contact. Head lice:
    • Cannot hop, jump, or fly, but they can crawl rapidly (23 cm per minute under normal conditions). 
    • Are not transmitted via pets — they only live on humans.
    • Are extremely unlikely to be transmitted by sharing hats, combs, or pillows. 
  • The life span of a louse is very short once it is detached from a human head (1–2 days), as lice are completely dependent on their human host for nutrition and warmth. 

[Leung, 2021; Nolt, 2022; Cummings, 2025]

How common is head lice infestation and what are the predisposing factors?

  • There is little information on the current prevalence of head lice infestation in the UK:
    • Analysis of the General Practice Research Database for diagnoses of headlice or prescription of parasiticidal agents in the West Midlands between 1993–2000 showed a peak of 28.2 diagnoses per 1000 patient/years in 1997 [Smith, 2003].
    • In a survey of 31 primary schools in Wales (n = 2793), live head lice were detected in 8.3% of children who were screened (95% CI 7.3 to 9.4) [Thomas et al, 2006].
  • Head lice infestation can affect anyone of any age. However, it is most common in children aged 4–11 years and is more common in girls than boys [BAD, 2024].
  • A 2020 systematic review (n=1,218,351) aimed to determine the worldwide prevalence of head lice in school children [Hatam-Nahavandi, 2020]:
    • The total prevalence was 19%, with a 7% prevalence in boys compared to 19% in girls.
    • The highest prevalence was in Central and South America (33%) with the lowest prevalence in Europe (5%).
  • Head lice can infest all types of hair [Nolt, 2022].
  • Published reports have not found that head lice infestation is significantly influenced by hair length or by frequent brushing or shampooing [Nolt, 2022; BAD, 2024]. 
  • There are no consistent findings in the medical literature that race or ethnicity influences the rate of infestation [Nolt, 2022].

What is the prognosis?

  • Head lice infestation is usually harmless, and the prognosis is excellent as most people respond to treatment. 
  • Treatment failure may result from: 
    • Inappropriate treatments.
    • Inadequate treatment (for example, exposure time too short, incorrect application, inadequate volume applied, uneven application). 
    • Development of product resistance. 
  • Re-infestation may occur if household members and close contacts are not examined and treated for infestation (where appropriate). 
  • Left untreated, head lice infestation may persist for long periods and lead to complications.

[Leung, 2021]

What are the complications of head lice infestation?

  • The complications of head lice infestation include:
    • Insomnia due to pruritus.
    • Impaired concentration at school or work. 
    • Excessive scratching, which may lead to bacterial infection, resulting in occipital or cervical lymphadenopathy.
    • Social stigma, psychological distress, and low self-esteem.
    • Absence from school or work.

[Leung, 2021]

Diagnosis of head lice

How should head lice infestation be confirmed?

  • A live louse must be found in order to confirm active head lice infestation.
    • An itching scalp is not sufficient to diagnose active infestation. 
    • The presence of louse eggs alone, whether hatched (nits) or unhatched, does not indicate active infestation. 
    • Lice found using detection combing at home can be attached to sticky tape and brought to the consultation to aid diagnosis.
  • Detection combing (the systematic combing of the hair with a fine-toothed head lice detection comb) is the most reliable way to confirm the presence of head lice, and it is much more reliable than visual inspection.
    • The detection comb should be made of plastic (metal combs are too harsh and may pull out hair) and have rigid teeth between 0.2–0.3 mm apart to trap head lice and their nymphs effectively.
    • Detection combing can be done on wet or dry hair. 
    • Less preparation is needed to comb dry hair, but wet combing is more accurate.
  • All members of the household and close contacts should also be checked for head lice.

Wet detection combing method

  • Wet detection combing takes 10–15 minutes per head, depending on hair length and type. 
  • To prepare the hair for wet detection combing, the family/carer of the person with suspected head lice should: 
    • Wash the hair using an ordinary shampoo.
    • Apply ample hair conditioner (to aid straightening and untangling of the hair).
    • Straighten and untangle the wet hair using a wide-toothed comb.
    • Switch to a detection comb once the wide-toothed comb is able to move freely through the hair without dragging.
  • To perform wet detection combing, they should: 
    • Slot the teeth of the detection comb into the hair at the roots so it is touching the scalp. 
    • Draw the detection comb through to the tips of the hair, maintaining contact with the scalp as long as possible. 
    • Check the comb for lice after each stroke, and remove them by wiping or rinsing the comb (good lighting is essential, and a magnifying glass may help). 
    • Work through the hair in sections until the whole head of hair has been combed thoroughly. 
    • Repeat the combing procedure to check for any lice that might have been missed the first time. 
    • Rinse out the conditioner.

[PHMEG, 2012; BAD, 2024; NHS Inform, 2026]

Dry detection combing method

  • Dry detection combing takes less time than wet detection combing. 
  • To prepare the hair for dry detection combing, the family/carer of the person with suspected head lice should:
    • Use an ordinary wide-toothed comb to straighten and untangle the hair. 
    • Switch to the detection comb once the wide-toothed comb is able to move freely through the hair without dragging.
  • To perform dry detection combing, they should: 
    • Comb the hair from the crown to the tips of the hair, working all around the head.
    • Comb each section of hair 3–4 times before moving to an adjacent section.
    • Look for lice as the comb is drawn through the hair. If a possible louse is seen, the person should trap it against the face of the comb using the thumb. This avoids the risk of the louse being repelled by static electricity as the comb is withdrawn from the hair.
    • Continue combing the hair in sections until the whole head of hair is combed through.

[NHS Inform, 2026]

Basis for recommendation

These recommendations are based on expert opinion in the Canadian Paediatric Society publication Head lice infestations: a clinical update [Cummings, 2025], International recommendations for an effective control of head louse infestations [Mumcuoglu, 2021], a narrative review Head lice [Nolt, 2022], the Public Health Medicine Environmental Group publication Head lice: Evidence-based guidelines based on the Stafford Report 2012 update [PHMEG, 2012], and the British Association of Dermatologists (BAD) leaflet Head lice [BAD, 2024].

Detection combing

  • Experts agree that the detection combing is a reliable method of diagnosing current, active infection with head lice [Mumcuoglu, 2021; Nolt, 2022; Cummings, 2025].
    • A study, published in 2008, found that detection combing was 3.84 times more effective than visual inspection for finding live lice [PHMEG, 2012].
    • Another study involving experienced parasitologists found that using a fine-toothed lice comb was four times more effective and twice as fast as visually examining the scalp to detect live head lice and diagnose an infestation [Cummings, 2025].
  • Limited evidence suggests that wet combing with conditioner may be the most sensitive diagnostic method; however, combing dry hair with a suitable plastic detection comb is quicker and nearly as good a technique for finding lice [Burgess, 2016; Mumcuoglu, 2021].
    • Preparation of wet hair with liberal conditioner prior to fine combing makes combing the hair and removal of lice easier than dry combing [Mumcuoglu, 2021].
    • Wet combing has a sensitivity of 91% for the detection of live lice and is more sensitive than dry combing or visual inspection [Leung, 2021]. 

What else might it be?

  • Head lice may be confused with pubic lice (Phthirus pubis) or body lice (Pediculus humanus). They can be distinguished by the location where they are found:
    • Head lice are found on the head. 
    • Pubic lice are found in pubic hair and other coarse hair, such as eyebrows, eyelashes, axillary hair, moustache, and beard. See the CKS topic on Pubic lice for more information.
    • Body lice are found on clothes, although they feed on the body. 
  • Nits may be confused with seborrhoeic scales, hair muffs (secretions from the hair follicle that are wrapped around the hair shaft), and particles from hair products (such as hair spray). 
    • Unlike nits, seborrhoeic scales, hair muffs, and hair spray particles can easily be brushed off.
  • Other causes of scalp itching include:
    • Other scalp conditions, such as eczema or seborrheic dermatitis.
    • A delayed reaction after the onset of infestation. Itch may not develop for several weeks or months and so could persist after successful eradication. 
    • Psychogenic itch after hearing that there are head lice within the school or community. 

Basis for recommendation

These recommendations are based on expert opinion in the Canadian Paediatirc Society publication Head lice infestations: a clinicial update [Cummings, 2025], narrative reviews Head lice [Nolt, 2022], Paediatrics: how to manage pediculosis capitis [Leung, 2021], and Lice and scabies: treatment update [Gunning, 2019], the Public Health Medicine Environmental Group publication Head lice: Evidence-based guidelines based on the Stafford Report 2012 update [PHMEG, 2012], and the British Association of Dermatologists (BAD) leaflet Head lice [BAD, 2024]. 

Management

Scenario: Management of head lice

From age 1 month onwards.

How should I manage a person with a confirmed head lice infestation?

  • The three main treatment options are:
    • Wet combing — this is the systematic combing of wet hair with a louse detection comb to remove head lice. 
      • The Bug Buster® kit and other nit combs are available on the NHS. For more information, see the Drug Tariff.
    • A physical insecticide — these silicone or fatty acid ester-based products kill the lice by physically coating their surfaces and suffocating them.
      • They include dimeticone 4% gel, lotion, or spray (other strengths of dimeticone products are also available); isopropyl myristate and cyclomethicone solution; and isopropyl myristate and isopropyl alcohol aerosol. 
    • A chemical insecticide — these poison the lice by chemical means. 
      • In the UK, the only chemical insecticide that is currently recommended is malathion 0.5% aqueous liquid, but resistance has been reported. 
  • The choice of treatment will depend on the preference of the person and/or their parents/carers after considering the advantages and disadvantages of each treatment, what has been previously tried, and the cost of the treatment. 
    • Wet combing or dimeticone 4% lotion is recommended first-line for pregnant or breastfeeding women, young children aged 6 months to 2 years, and people with asthma or eczema. 
    • Shampoo treatments are generally not recommended because they are less effective than lotions, as they are diluted too much and have an insufficient contact time to kill eggs.
  • Supply enough treatment to complete a treatment course. 
    • In general, a small bottle of insecticide is sufficient for treating short or shoulder-length hair, but a larger bottle or two small bottles would be needed for longer, thicker hair.
  • Give additional information and advice, including on how to use the treatment, how to check that treatment has been successful, and how to reduce the risk of reinfestation. 

Basis for recommendation

These recommendations are based on expert opinion in the Canadian Paediatric Society publication Head lice infestations: a clinical update [Cummings, 2025], International recommendations for an effective control of head louse infestations [Mumcuoglu, 2021], a narrative review Head lice [Nolt, 2022], the Public Health Medicine Environmental Group publication Head lice: Evidence-based guidelines based on the Stafford Report 2012 update [PHMEG, 2012], the British Association of Dermatologists (BAD) leaflet Head lice [BAD, 2024], and the British national Formulary [BNF, 2026]. 

 

Choice of treatment
  • There is a lack of consensus amongst experts on the preferred initial treatment choice. The recommendation that it depends on factors such as contraindications and cautions (including the age of the person), the person's choice, what has been tried before, and cost is therefore pragmatic. 
  • The recommendations for managing women who are pregnant or breastfeeding, young children, and people with scalp dermatitis or asthma is based on the BAD patient information leaflet [BAD, 2024].
  • Expert opinion in an international guideline [Mumcuoglu, 2021], the BAD leaflet [BAD, 2024], and the BNF [BNF, 2026], is that insecticide products with a short contact time, which are applied to wet or damp hair (such as insecticide shampoos), are not generally recommended as there are concerns that they become too dilute when used to be effective. 
Treatment efficacy
  • Wet combing
  • Physical insecticides
    • Dimeticone kills lice by creating a physical barrier around them. A 2016 review found dimeticone superior to other traditional lice treatments with no increased adverse events [Kolber, 2016]. Cure rates in European RCTs were 83-92%, dropping to 70% in long-standing cases. A 2020 meta-analysis suggested superiority or non-inferiority of occlusive products over traditional neurotoxic pediculocides [Flores-Genuino, 2020].
    • Isopropyl myristate and cyclomethicone kills head lice by dissolving the wax coating on the louse exoskeleton, leading to uncontrollable dehydration. Cure rates of 52% and 82% have been reported in clinical trials in the UK [Kaul et al, 2007; Burgess et al, 2008].
    • Experts advise that while it is widely believed that physical treatments are not susceptible to resistance this is not the case [Burgess, 2022; Burgess, 2023]. 
  • Malathion 0.5% aqueous liquid
    • Cure rates of 75% and 33% have been reported in clinical trials of two applications one week apart [Roberts, 2000; Burgess et al, 2007]. Resistance to malathion and low cure rates have been reported [Hill et al, 2005].
    • Expert opinion in in a narrative review is that malathion liquid 0.5% is severely affected by resistance and should no longer be used [Burgess, 2016]. 
Treatments not recommended
  • The insecticide permethrin is active against head lice but the formulation and licensed methods of application (a 15-minute shampoo treatment) makes it unsuitable for the treatment of head lice [BNF, 2026]. 
  • The following products are not recommended for the treatment of head lice infestation due to a lack of consistent evidence for their safety and efficacy: 
    • Herbal and essential oil preparations (such as lavender oil, or eucalyptus oil)  [BAD, 2024; Nolt, 2022]. 
    • Electric combs — in addition, expert consensus is that they should not be used because they are expensive and can pose a safety risk if used incorrectly [PHMEG, 2012]. 
    • Dry air devices [PHMEG, 2012]. 

What information and advice should I offer?

  • Advise the person with head lice and/or their parents/carers to read the instructions that come with the treatment to ensure that it is used safely and correctly. Highlight that:
    • All affected family members should be treated on the same day to avoid reinfection. 
  • For wet combing, advise that:
    • They should wash their hair with ordinary shampoo, then apply lots of conditioner, then comb the whole head of hair using a detection comb from the roots to the end. 
    • The process should be performed on days 1, 5, 9, and 13. 
    • It takes about 10 minutes to complete the process on short hair, and 20–30 minutes for long, frizzy, or curly hair. Two combing procedures are recommended at each treatment session. 
    • The hair should be checked again on day 17. 
    • The charity Community Hygiene Concern (www.chc.org) has a video about the wet combing method on its website. 
  • For insecticides, advise that:
    • Treatment should be applied to all areas of the dry scalp and to all of the hairs, from their roots to their tips. 
    • The product should be left on for the time recommended by the manufacturer, then washed off. This varies from 15 minutes to at least 8 hours. A contact time of 8–12 hours (or overnight) is recommended for lotions and liquids. 
    • It is generally recommended that insecticides be applied twice, at least 7 days apart, in order to treat any lice hatching from eggs before they lay more eggs themselves. 
    • Inappropriate use can lead to treatment failure and may increase the risk of resistant lice. 
    • During treatment, hair should be kept away from open flames or other sources of ignition as dimeticone-containing products are combustible when on the hair and in direct contact with an open flame or other source of ignition. 
    • After treatment is complete the hair should be checked every week for a month to ensure the infestation has cleared. 
    • Treatments is successful if no living lice are found on the scalp. 
  • Explain that the presence of louse eggs alone (whether hatched [nits] or unhatched) and/or itching do not indicate treatment failure. 
    • Itch in response to chemical agents may persist for many days and itch from the infestation may persist for 2–3 weeks after successful treatment. 
  • Give general advice, including that:
    • Children who are being treated for head lice can still attend school. 
    • There is no evidence that head lice have a preference for either clean or dirty hair. 
    • Environmental cleaning is not necessary as lice do not survive away from the head and so an unlikely route of transmission 
      • Only items that have been in contact with the head within 2 days before treatment should be considered. 
    • No treatment can guarantee success. However, a treatment has the best chance of success if it is performed correctly and if all affected household members are treated on the same day. 
    • Essential oil-based treatments and herbal treatments are not recommended due to the lack of good-quality evidence on their safety and efficacy. 
    • It is not possible to prevent head lice infestation. However, children of primary school age should be examined regularly (for example, weekly) at home to identify infestation early. 
    • The following measures are not recommended for preventing head lice transmission:
      • Products marketed as head lice repellents. 
      • Repeated use of head lice treatments in the absence of live lice. 
      • Measures beyond normal personal hygiene, house cleaning, and laundry (for example, spraying pesticides, or freezing personal items).
  • Provide additional information on head lice.

Basis for recommendation

These recommendations are based on expert opinion in the Canadian Paediatric Society publication Head lice infestations: a clinical update [Cummings, 2025], International recommendations for an effective control of head louse infestations [Mumcuoglu, 2021], narrative reviews Head lice [Nolt, 2022], and Head lice: resistance and treatment options [Burgess, 2016], the Public Health Medicine Environmental Group publication Head lice: Evidence-based guidelines based on the Stafford Report 2012 update [PHMEG, 2012], the British Association of Dermatologists (BAD) leaflet Head lice [BAD, 2024], the British National Formulary, [BNF, 2026], the summaries of product characteristics for Hedrin 4% cutaneous solution [EMC, 2020], and Derbac M [MHRA, 2025], and the NHS patient information on Head lice and nits [NHS, 2024].

Treatment advice
  • Manufacturers of insecticide products advise that two applications are necessary, and the second treatment should be used after 7 days [EMC, 2020; MHRA, 2025]. The BNF [BNF, 2026] advises they should be used once a week for 2 weeks. Experts advise that the second application should be done 7–10 days after the first application [Nolt, 2022; Cummings, 2025] to kill the lice that have hatched after the first application [Mumcuoglu, 2021].
    • Hatchlings can emerge after 6 to 10 days. Any egg more than 12 days old has hatched or contains a dead embryo [Mumcuoglu, 2021].
Checking success of treatment
  • This recommendation is based on the fact that no treatment for head lice is completely ovicidal, and it is possible that eggs laid on the morning of a treatment session could survive treatment and hatch live head lice after the completion of a course of treatment. 
  • Opinions differ on when hair should be re-examined after treatment. 
    • One expert [Mumcuoglu, 2021] recommends re-examining one day after the final treatment and again after 10 days, while BAD recommends the hair should be checked every week for a month to ensure the infestation has cleared [BAD, 2024]. Expert opinion in a narrative review is that the follow-up check should be done at least 7 days after the last application of treatment to allow for any eggs that survive the treatment and/or eggs that hatch later than expected [Burgess, 2016]. 
      • The author highlighted that a retrospective examination of data from around 20 clinical trials found that in a small proportion of thoroughly treated people, a few louse eggs hatched up to 13 days after the first treatment.
    • Advice from BAD [BAD, 2024] and Community Hygiene Concern (www.chc.org) is that after wet combing detection combing should be done on days 1, 5, 9, and 12/13 to avoid risks of continuing infestation. 
Additional advice
  • The British Association of Dermatologists (BAD) [BAD, 2024] advises that children with head lice do not need to be kept off school as long as treatment advice is followed. This approach is supported by other experts [Cummings, 2025]. 
  • Expert opinion in narrative reviews is that environmental cleaning is not necessary as the lifespan of a head louse is very short (1–2 days) once it is detached from a human head [Cummings, 2025; Nolt, 2022].
    • Washing items in close or prolonged contact with the head (such as hats, pillow cases, brushes and combs) may be useful. These items should be washed at 66°C or over and dried in a hot dryer for 15 minutes. Alternatively storing items in a sealed plastic bag for 2 weeks will kill live lice and nits [Cummings, 2025]. 
    • This view is supported by an American Academy of Pediatrics clinical report [Nolt, 2022] which states that it is advisable to clean hair care items and bedding used by the individual with the infestation, and that only items that have been in contact with the head of the person with infestation within 2 days before treatment should be considered for cleaning.
    • The role of fomite transmission remains controversial [Cummings, 2025]. 
    • There is no evidence that measures beyond normal personal hygiene, house cleaning, and laundry can prevent reinfestation [Burgess, 2016; Nolt, 2022].
  • Regular detection combing is recommended as it is the best way to identify a head lice infestation quickly [Mumcuoglu, 2021]. 
  • Experts agree that repellents should not be used as there is no evidence to support their use.
    • There is no evidence that head lice treatments used prophylactically are effective [Burgess, 2016], and there is concern that prophylactic use of insecticidal treatments could increase the risk of toxic effects. They should only be used if a live louse is found [Mumcuoglu, 2021].
  • Opinion from previous reviewers of this CKS topic was divided regarding the length of time itch may persist after successful treatment: some suggested a few days, whilst others suggested that itch may persist for 2–3 weeks after successful eradication [PHMEG, 2012].

How should I manage treatment failure?

  • If a live louse is found after treatment with an insecticide:
    • Check that the following were used: a complete treatment course, correct application technique, correct application time, and sufficient volume of product to cover hair adequately. 
    • Advise that household members, close family, and close friends (both adults and children) should be assessed to identify possible sources of reinfestation.
    • Repeat the same treatment, ensuring that it is undertaken correctly and all people are treated simultaneously, or switch to a different treatment as appropriate.
      • If malathion has been used, consider the possibility of resistance.
  • If a live louse is found after treatment by wet combing (that is, a live louse is found on day 17):
    • Check that the following were used: the correct combing technique, sufficient duration of combing, and sufficient combing sessions. 
    • Advise that household members, close family, and close friends (both adults and children) should be assessed to identify possible sources of reinfestation. 
    • Advise the person to repeat wet combing or consider using an appropriate insecticide.
  • Whichever second-line treatment strategy is chosen:

Basis for recommendation

These recommendations are based on expert opinion in the Canadian Paediatric Society publication Head lice infestations: a clinical update [Cummings, 2025], International recommendations for an effective control of head louse infestations [Mumcuoglu, 2021], narrative reviews Head lice [Nolt, 2022], and Head lice: resistance and treatment options [Burgess, 2016], the Public Health Medicine Environmental Group publication Head lice: Evidence-based guidelines based on the Stafford Report 2012 update [PHMEG, 2012], the British National Formulary, [BNF, 2026], and the NHS patient information on Head lice and nits [NHS, 2024].

Supporting evidence

This CKS topic is largely based on the Canadian Paediatric Society publication Head lice infestations: a clinical update [Cummings, 2025], International recommendations for an effective control of head louse infestations [Mumcuoglu, 2021], narrative reviews Head lice [Nolt, 2022], and Head lice: resistance and treatment options [Burgess, 2016], the Public Health Medicine Environmental Group publication Head lice: Evidence-based guidelines based on the Stafford Report 2012 update [PHMEG, 2012], and the British Association of Dermatologists (BAD) leaflet Head lice [BAD, 2024]. The rationale for individual recommendations is outlined in the relevant basis for recommendation sections of the topic.

How this topic was developed

This section briefly describes the processes used in developing and updating this topic. Further details on the full process can be found in the About Us section and on the Clarity Informatics website.

Search strategy

A literature search was conducted for guidelines, systematic reviews and randomized controlled trials on primary care management of head lice.

Search dates

October 2021 - May 2026

Key search terms

Various combinations of searches were carried out. The terms listed below are the core search terms that were used for Medline.

  • exp pediculus/, head lice.tw, headlice.tw, head louse.tw, lice infestations/, pediculus.tw, pediculosis.tw, pediculide$.tw*
  • Antiparasitic Agents/therapeutic use*

Sources of guidelines

Sources of systematic reviews and meta-analyses

  • The Cochrane Library:
    • Systematic reviews
    • Protocols
    • Database of Abstracts of Reviews of Effects
  • Medline (with systematic review filter)
  • EMBASE (with systematic review filter)

Sources of health technology assessments and economic appraisals

Sources of randomized controlled trials

  • The Cochrane Library:
    • Central Register of Controlled Trials
  • Medline (with randomized controlled trial filter)
  • EMBASE (with randomized controlled trial filter)

Sources of evidence based reviews and evidence summaries

Sources of national policy

Patient experiences

Sources of medicines information

The following sources are used by CKS pharmacists and are not necessarily searched by CKS information specialists for all topics. Some of these resources are not freely available and require subscriptions to access content.

Stakeholder engagement

Our policy

The external review process is an essential part of CKS topic development. Consultation with a wide range of stakeholders provides quality assurance of the topic in terms of:

  • Clinical accuracy.
  • Consistency with other providers of clinical knowledge for primary care.
  • Accuracy of implementation of national guidance (in particular NICE guidelines).
  • Usability.

Principles of the consultation process

  • The process is inclusive and any individual may participate.
  • To participate, an individual must declare whether they have any competing interests or not. If they do not declare whether or not they have competing interests, their comments will not be considered.
  • Comments received after the deadline will be considered, but they may not be acted upon before the clinical topic is issued onto the website.
  • Comments are accepted in any format that is convenient to the reviewer, although an electronic format is encouraged.
  • External reviewers are not paid for commenting on the draft topics.
  • Discussion with an individual or an organization about the CKS response to their comments is only undertaken in exceptional circumstances (at the discretion of the Clinical Editor or Editorial Steering Group).
  • All reviewers are thanked and offered a letter acknowledging their contribution for the purposes of appraisal/revalidation.
  • All reviewers are invited to be acknowledged on the website. All reviewers are given the opportunity to feedback about the external review process, enabling improvements to be made where appropriate.

Stakeholders

  • Key stakeholders identified by the CKS team are invited to comment on draft CKS topics. Individuals and organizations can also register an interest to feedback on a specific topic, or topics in a particular clinical area, through the Getting involved section of the Clarity Informatics website.
  • Stakeholders identified from the following groups are invited to review draft topics:
    • Experts in the topic area.
    • Professional organizations and societies (for example, Royal Colleges).
    • Patient organizations, Clarity has established close links with groups such as Age UK and the Alzheimer’s Society specifically for their input into new topic development, review of current topic content and advice on relevant areas of expert knowledge.
    • Guideline development groups where the topic is an implementation of a guideline.
    • The British National Formulary team.
    • The editorial team that develop MeReC Publications.
  • Reviewers are provided with clear instructions about what to review, what comments are particularly helpful, how to submit comments, and declaring interests.

Patient engagement

Clarity Informatics has enlisted the support and involvement of patients and lay persons at all stages in the process of creating the content which include:

  • Topic selection
  • Scoping of topic
  • Selection of clinical scenarios
  • First draft internal review
  • Second draft internal review
  • External review
  • Final draft and pre-publication

Our lay and patient involvement includes membership on the editorial steering group, contacting expert patient groups, organizations and individuals.

Evidence exclusion criteria

Our policy

Scoping a literature search, and reviewing the evidence for CKS is a methodical and systematic process that is carried out by the lead clinical author for each topic. Relevant evidence is gathered in order that the clinical author can make fully informed decisions and recommendations. It is important to note that some evidence may be excluded for a variety of reasons. These reasons may be applied across all CKS topics or may be specific to a given topic.

Studies identified during literature searches are reviewed to identify the most appropriate information to author a CKS topic, ensuring any recommendations are based on the best evidence. We use the principles of the GRADE and PICOT approaches to assess the quality of published research. We use the principles of AGREE II to assess the quality of published guidelines.

Standard exclusions for scoping literature:

  • Animal studies
  • Original research is not written in English

Possible exclusions for reviewed literature:

  • Sample size too small or study underpowered
  • Bias evident or promotional literature
  • Population not relevant
  • Intervention/treatment not relevant
  • Outcomes not relevant
  • Outcomes have no clear evidence of clinical effectiveness
  • Setting not relevant
  • Not relevant to UK
  • Incorrect study type
  • Review article
  • Duplicate reference

Organizational, behavioural and financial barriers

Our policy

The CKS literature searches take into consideration the following concepts, which are discussed at the initial scoping of the topic.

  • Feasibility
    • Studies are selected depending on whether the intervention under investigation is available in the NHS and can be practically and safely undertaken in primary care.
  • Organizational and Financial Impact Analysis
  • Studies are selected and evaluated on whether the intervention under investigations may have an impact on local clinical service provision or national impact on cost for the NHS. The principles of clinical budget impact analysis are adhered to, evaluated and recorded by the author. The following factors are considered when making this assessment and analysis.
    • Eligible population
    • Current interventions
    • Likely uptake of new intervention or recommendation
    • Cost of the current or new intervention mix
    • Impact on other costs
    • Condition-related costs
    • In-direct costs and service impacts
    • Time dependencies
  • Cost-effectiveness or cost-benefit analysis studies are identified where available. 

We also evaluate and include evidence from NICE accredited sources which provide economic evaluations of recommendations, such as NICE guidelines. When a recommended action may not be possible because of resource constraints, this is explicitly indicated to healthcare professionals by the wording of the CKS recommendation.

Declarations of interest

Our policy

Clarity Informatics requests that all those involved in the writing and reviewing of topics, and those involved in the external review process to declare any competing interests. Signed copies are securely held by Clarity Informatics and are available on request with the permission of the individual. A copy of the declaration of interest form which participants are asked to complete annually is also available on request. A brief outline of the declarations of interest policy is described here and full details of the policy is available on the Clarity Informatics website. Declarations of interests of the authors are not routinely published, however competing interests of all those involved in the topic update or development are listed below. Competing interests include:

  • Personal financial interests
  • Personal family interest
  • Personal non-financial interest
  • Non-personal financial gain or benefit

Although particular attention is given to interests that could result in financial gains or losses for the individual, competing interests may also arise from academic competition or for political, personal, religious, and reputational reasons. An individual is not obliged to seek out knowledge of work done for, or on behalf of, the healthcare industry within the departments for which they are responsible if they would not normally expect to be informed.

Who should declare competing interests?

Any individual (or organization) involved in developing, reviewing, or commenting on clinical content, particularly the recommendations should declare competing interests. This includes the authoring team members, expert advisers, external reviewers of draft topics, individuals providing feedback on published topics, and Editorial Steering Group members. Declarations of interest are completed annually for authoring team and editorial steering group members, and are completed at the start of the topic update and development process for external stakeholders.

Competing interests declared for this topic:

None.

References

  • BAD (2024) Head lice. Brisith Association of Dermatologists. https://www.bad.org.uk [Free Full-text]
  • BNF (2026) British National Formulary. National Institute for Health and Care Excellence. https://bnf.nice.org.uk [Free Full-text]
  • Burgess, I.F., Lee, P.N. and Matlock, G. (2007) Randomised, controlled, assessor blind trial comparing 4% dimeticone lotion with 0.5% malathion liquid for head louse infestation. PLoS ONE 2(11). [Abstract]
  • Burgess, I.F., Lee, P.N. and Brown, C.M. (2008) Randomised, controlled, parallel group clinical trials to evaluate the efficacy of isopropyl myristate/cyclomethicone solution against head lice. Pharmaceutical Journal 280(Mar), 371-375. [Abstract]
  • Burgess, I.F. (2016) Head lice: resistance and treatment options. Pharmaceutical Journal 297(7893). [Free Full-text]
  • Burgess, I.F. (2022) Physically acting treatments for head lice — can we still claim they are ‘resistance proof’? Pharmaceutics 14(11), 2430. [Abstract]
  • Burgess, I.F. and Brunton, E.R. (2023) Head lice: evidence that resistance to physically acting treatments is developing. British Journal of Dermatology 189(1), 144-145. [Abstract]
  • Cummings, C., Finlay, J.C., MacDonald, N.E. et al. (2025) Head lice infestations: a clinical update. Canadian Paediatric Society. https://cps.ca [Free Full-text]
  • EMC (2020) SPC for Hedrin 4% cutaneous solution. Electronic Medicines Compendium. Datapharm Communications Ltd. https://www.medicines.org.uk/emc [Free Full-text]
  • Flores-Genuino, R. N. S., Gnilo, C. M. S. and Dofitas, B. L. (2020) Occlusive versus neurotoxic agents for topical treatment of head lice infestation: A systematic review and meta-analysis. Pediatr Dermatol 37(1), 86-92. [Abstract]
  • Gunning, K., Kiraly, B. and Pippitt, K (2019) Lice and scabies: treatment update. American Family Physician 99(10), 635-642. [Abstract]
  • 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. [Free Full-text]
  • 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. [Abstract]
  • Kaul,N., Palma,K.G., Silagy,S.S., et al. (2007) North American efficacy and safety of a novel pediculicide rinse, isopropyl myristate 50% (Resultz). Journal of Cutaneous Medicine & Surgery. 11(5), 161-167. [Abstract]
  • Kolber, M. R., Pierse, M. and Nickonchuk, T. (2016) The louse is (no longer) in the house. Canadian Family Physician 62(4), 322. [Free Full-text]
  • Leung, A.K.C., Lam, J.M., Leong, K.F. et al. (2021) Paediatrics: how to manage pediculosis capitis. Drugs Context 11. [Abstract]
  • MHRA (2025) SPC for Derbac M Liquid. Medicines and Healthcare products Regulatory Agency. https://products.mhra.gov.uk [Free Full-text]
  • Mumcuoglu, K. Y., Pollack, R. J., Reed, D. L., et al. (2021) International recommendations for an effective control of head louse infestations. International Journal of Dermatology 60(3), 272-280. [Free Full-text]
  • NHS Inform (2026) Head lice and nits. NHS Inform. https://www.nhsinform.scot [Free Full-text]
  • NHS (2024) Head lice and nits. NHS. https://www.nhs.uk [Free Full-text]
  • Nolt, D., Moore, S., Yan, A.C. et al. (2022) Head lice. Pediatrics 150(4), e2022059282.. [Abstract]
  • PHMEG (2012) Head lice: evidence-based guidelines based on the Stafford Report. 2012 update. Public Health Medicine Environmental Group. http://www.phmeg.org.uk [Free Full-text]
  • Roberts, R.J., Casey, D., Morgan, D.A. et al. (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. [Abstract]
  • Smith, S., Smith, G., Heatlie, H., et al. (2003) Head lice diagnosed in general practice in the West Midlands between 1993 and 2000: a survey using the General Practice Research Database. Commun Dis Public Health 6(2), 139-143. [Free Full-text]
  • Thomas, D.R., McCarroll, L., Roberts, R., et al. (2006) Surveillance of insecticide resistance in head lice using biochemical and molecular methods. Archives of Diseases in Childhood 91(9), 777-778. [Abstract]
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