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HEAD LICE: Supporting families with evidence-based treatment advice

MODULE SUMMARY

NICE guidance (updated 2016) provides robust evidence-based advice about detecting and treating head lice.1 This module will help develop and strengthen your understanding of the guidance, so that you can be confident that you are offering parents up-to-date information and practical treatment advice. 

 

LEARNING OBJECTIVES

After studying this module you should:

  • understand how head lice spread
  • know how to detect head lice
  • be aware of the recommended treatment options


NEXT STEPS

  • Read the clinical review: if you don't have a printed version, click here to download a pdf
  • Complete the online assessment
  • Receive CPD credit

AUTHOR(S)

Written by Karen J Stocker BSc (Hons)
Reviewed by Professor Dave Clarke PhD, MA (Ed), PGDip, BSc (Hons), RGN, RSCN

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    The content of this website is subject to editorial review however you should seek independent validation where required. Content on the website is correct at the time of publishing, and will be reviewed every 2 years aligned to medical best practice.

     

    Pre-learning reflection

    Please take a moment to answer these pre-learning questions.  Once completed, click 'next step' below to start this module.  These answers will be logged on your CPD certificate which will be emailed to you on completion as evidence of your learning.


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    Head lice: A common problem


    Head louse infestation (pediculosis capitis) is an old and extremely common problem. Despite the availability of effective treatments, it continues to affect millions of people of all ages worldwide. With transmission occurring almost exclusively through direct head-to-head contact, children of primary school age (4-11 years) tend to be most frequently affected, with a peak incidence occurring at 7-8 years.1

    National Institute for Health and Care Excellence (NICE) guidance (last updated 2016) provides robust evidence-based advice about detecting and treating head lice.1 This module will help develop and strengthen your understanding of the guidance, so that you can be confident that you are offering parents the up-to-date information and practical treatment advice they need.

     

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    The impact of infestation

     

    Infestations vary from just a few lice to more than a thousand in severe cases, but a typical infestation is about 30 lice per head.1 They can be difficult to spot and many people who unknowingly have lice remain asymptomatic. Itching is the most common symptom and increases with duration of infestation and number of lice. However, itching may not develop for weeks or months and may continue for weeks after the head lice are gone.

    Head lice don’t cause significant health problems. However, the feeling of lice moving through the hair can be a nuisance, and without  treatment, head lice can persist for long periods. This may lead to complications including:

    • a pruritic rash on the back of the neck and behind the ears, caused by a hypersensitivity reaction to louse saliva/faeces
    • excoriation and secondary bacterial infection (e.g. impetigo)
    • loss of sleep due to continuous itching.

    Persistently disturbed sleep may lead to concentration problems, tiredness and poor performance in school. As people mistakenly believe that the condition stems from poor hygiene, head lice can cause considerable anxiety, distress and stigma for affected individuals and their families.

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      The role of healthcare professionals

      Every generation of parents needs instruction, encouragement and support from healthcare professionals to help them become proactive and proficient in detecting and treating head lice. Ideally, healthcare professionals should provide parents with information about head lice before their children start school and at regular intervals throughout the primary school years.


      Debunking common myths

      • Anyone who has hair can catch head lice – they don’t care if hair is dirty or clean.
      • Head lice can crawl quickly along a hair – but they can’t burrow under skin, jump, swim or fly.
      • Head lice spread by direct head-to-head contact – transmission via clothes and pillows is extremely unlikely.
      • Pets can’t spread head lice – they only live on humans.
      • A ‘nit’ is an empty egg case – finding ‘nits’ doesn’t necessarily mean you have head lice.

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      Anatomy

      The head louse (Pediculus humanus capitis) is an obligate parasite. It is a highly-specialised, haematophagic (blood-sucking) insect, which completes its entire life-cycle on the human head.

      The adult louse is a six-legged, wingless insect not much bigger than a sesame seed (about 3 mm long). Its abdomen has seven segments. The first six have a tiny opening (spiracle) on each side, leading to a network of tubes that facilitate gaseous exchange. The spiracles also provide a route for water transpiration.

      The louse generally stays close to its host’s scalp. It uses its piercing mouthparts to inject saliva and extract a blood meal several times a day. It is usually grey, but may take on a reddish-brown hue after feeding. Each leg ends in a pincer-like claw which enables it to grip the hair. African-Americans appear less likely to be infested with head lice than other ethnic groups.2 It may be that the louse is less able to grasp their hair, which is wider and oval in cross-section rather than circular.

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      Life cycle

      The entire life cycle from an egg being laid to the death of the adult head louse is completed in 30 days.

      Following mating, the adult female can lay 6 to 8 oval-shaped eggs (ova) a day – about 50-150 eggs during her lifetime. She attaches each egg near to the base of a hair by means of a ‘glue’ secreted from her abdomen. The glue rapidly hardens to form a sheath which covers the hair shaft and most of the egg, except for its cap (the operculum). Each egg is about 0.8 mm long and translucent. After 7-10 days (depending on environmental conditions) an immature louse (nymph) emerges from the egg. The nymph is about the size of a pin-head and pearly white. The nymph sheds its exoskeleton (moults) three times before becoming a sexually mature adult, 7-10 days after hatching. The empty egg case (or ‘nit’) turns white, but (unlike dandruff and other debris which may be mistaken for lice eggs) will remain firmly attached to the growing hair even after vigorous brushing.

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      Transmission

      Transmission requires direct head-to-head contact. Head lice can’t jump, fly or swim, but they can crawl rapidly along hairs from one head to another. Children tend to be most affected because they often have head-to-head contact in class and during play. The trend to take ‘selfie’ photos with heads together also provides an opportunity for lice to spread.

      Lice can’t survive long once detached from the head. Deprived of blood meals, lice become too dehydrated to feed within 8-12 hours and die within 1-2 days. Lice are extremely unlikely to spread by sharing hats, combs, or pillows. However, head lice caught in combs and brushes, or clinging to stray hairs in them, could be returned to the head at the next stroke.1

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      Detection

      Healthcare professionals should encourage parents to examine their children’s hair regularly so that head lice can be identified and treated early.

      Itching shouldn’t be assumed to indicate an active infestation. Itching may be caused by skin conditions, such as eczema or psoriasis, or prompted by hearing that there are lice in the community. As it’s difficult to distinguish between viable eggs and empty shells, the presence of eggs can’t be assumed to indicate an active infestation either. A live louse must be found to confirm an active infestation.

      Systematic combing using a fine-toothed detection comb is the most reliable way to confirm the diagnosis. The detection comb should be made of plastic and have teeth 0.2-0.3 mm apart.1 Combing may be done on wet or dry hair, but wet combing is more reliable as wet lice remain immobile and are easily removed at the same time. Good lighting and a magnifying glass can help.

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      Wet combing detection procedure

      Instructions for wet combing should be provided with detection combs, but generally the procedure is as follows:

      • After washing hair, apply ample conditioner and leave it in.
      • Untangle hair using an ordinary comb.
      • Once the comb moves freely, switch to a detection comb.
      • Slot the detection comb into the hair at the roots.
      • Draw the comb through to the tips of the hair, maintaining contact with the scalp as long as possible.
      • Check the comb for lice after every stroke, and remove them by wiping or rinsing the comb.
      • Work through the hair in sections until all hair has been combed thoroughly.
      • Rinse out conditioner.
      • Repeat the combing procedure to check for lice that may have been missed the first time.

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      Check close contacts

      If a live head louse is found, all household members and close contacts should be checked for head lice. Treatment should only be given if an active head louse infestation is confirmed and then all affected household members should be treated simultaneously.

      Parents should let their child’s school know so that families with children in the same class and other close contacts can be reminded to check regularly for head lice. However, it is unnecessary for children who have head lice to be kept away from school or nursery.3

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      Treatment options

      There are many head lice treatments available. However, NICE only recommends the treatments detailed (see panel) for which there is evidence of safety and efficacy.1 NICE believes that the data available doesn’t show any one of these options to be clearly superior. Parents should be assisted to choose a treatment according to their individual needs and preferences after considering the advantages and disadvantages of each, what if anything they have already tried, and the cost.

      • NICE recommends wet combing or 4% dimeticone lotion first-line for pregnant or breastfeeding women, children aged 6 months to 2 years, and those with asthma or eczema.
      • Chemical insecticides should only be used with medical supervision in children younger than 6 months
      • Alcohol-based preparations should not be used in very young children or in people with asthma or scalp dermatitis.
      Whichever treatment is chosen, you should ensure parents check the product’s suitability for their child (or whoever needs treating) and remind them to follow all the instructions carefully.

       

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      Wet combing

      Systematic combing of wet hair (using the procedure given previously) with a detection comb can be used to physically remove lice.

      The comb must be carefully cleaned of lice after every stroke. The recommended method involves four combing sessions over 2 weeks (on days 1, 5, 9 and 13). Each session should take about 10 minutes on short hair, but can take up to 30 minutes on long or curly hair.

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      Chemical insecticides

      Currently, malathion 0.5% aqueous liquid is the only chemical insecticide recommended for treating head lice in the UK. Phenothrin and carbaryl are no longer available, and there is evidence of substantial resistance to permethrin. However, resistance to malathion has already been reported.

      Malathion works by blocking cholinesterase, leading to an excess of acetylcholine, causing paralysis and death. The treatment has to be massaged into the dry hair and scalp, left to dry naturally for 12 hours (or overnight) then washed off with shampoo. It needs to be applied twice, 7 days apart to kill any lice hatching in the intervening period. Dead lice and nits can then be removed with a fine-toothed nit comb.

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      Physical insecticides

      These treatments have a physical mode of action, so resistance is unlikely to develop. They need to be applied to all of the scalp and hair, left on for the recommended treatment time (which varies from 10 minutes to at least 8 hours for some products) and then washed off. Dead lice and nits can then be removed with a fine-toothed nit comb.

      The Medicines and Healthcare Products Regulatory Agency (MHRA) issued advice concerning risk of serious burns if treated hair is exposed to sources of ignition.4 Parents should be advised on the safe and correct use of treatments and if appropriate, advised not to smoke around treated hair and to keep it away from open flames or other sources of ignition, including in the morning after overnight application until hair is washed.

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      Physical insecticides: Dimeticone

      Dimeticone immobilises head lice by coating them with an oily substance. This occludes the spiracles, depriving the louse of oxygen and preventing water transpiration, which leads to internal water accumulation and death.

      Dimeticone 4% lotion has a well-established safety profile but has limited ovicidal activity. Dimeticone 92% spray has better ovicidal activity. Using this formulation, a cure rate of 97% was reported in one clinical trial.1 However there is a lack of safety data on its use in pregnant or breastfeeding women and in children younger than 2 years. Safety data for these groups is also lacking for dimeticone >95% lotion, and there are no published clinical trials on its use.

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      Physical insecticides: Isopropyl myristate

      Isopropyl myristate destroys lice by dissolving the waxy coating on their exoskeleton, leading to uncontrollable dehydration and death.

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      Checking treatment success

      After treatment, parents should be encouraged to carry out detection combing to confirm treatment success. This should be done on day 17 if wet combing. Opinions differ as to when the hair should be checked after using an insecticide treatment.

      If there is no advice given with the product, you can suggest detection combing is done either:

      • 2-3 days after completing a course of treatment and again 7 days later, or
      • on days 5, 9 and 12/13 after the first treatment application.

      If live lice are again detected:
      • check parents followed the treatment instructions correctly
      • reiterate appropriate treatment advice (see panel)
      • advise that household members, close family and friends are assessed to identify possible sources of reinfestation
      • advise parents to repeat the treatment or switch to one of the other recommended treatments, as appropriate (if malathion was used, consider the possibility of resistance)
      • ensure all affected contacts are treated simultaneously.
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      Summary

      • Head lice can affect anyone, but are particularly common in primary school children.
      • Although head lice are of little clinical concern, they do cause a great deal of distress.
      • Parents should carry out detection combing regularly.
      • Head lice treatments should only be used if live lice are definitely seen.
      • NICE only recommends a limited number of treatments for which there is evidence of safety and efficacy.
      • NICE believes that the available data doesn’t show any one of these treatment options to be clearly superior.
      • There are various pros and cons to consider when choosing one of the recommended treatment options.
      • NICE recommends wet combing or 4% dimeticone lotion first-line for pregnant or breastfeeding women, children aged 6 months to 2 years, and those with asthma or eczema.
      • Treatment has the best chance of success if applied correctly and all affected contacts are treated simultaneously.
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      Assessment - Anatomy

      Now that you have reviewed the learning, please complete the following multiple choice questions to test what you've learnt and receive your CPD certificate. 

       
      Approximately, how big is an adult head louse?
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      Assessment - Life cycle

      A female louse can lay 6 to 8 ova per day, but how long does it take for them to hatch?
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      Assessment - Detection

      Systematic combing with a fine-toothed detection comb is the most reliable way to detect head lice, but how far apart should the teeth of the detection comb be?
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      Assessment - Treatment

      Wet combing can be time-consuming. If a parent chooses to use the wet combing procedure to remove their child’s head lice, how many sessions of combing will they need to complete in the first 2 weeks?
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      Assessment - Treatment 

      Wet combing and dimeticone 4% lotion are the first-line treatment options for pregnant and breastfeeding women. If a woman chooses to use dimeticone 4% lotion, how long will she need to leave it on her hair before she can wash it off?
      (NB: Always read the label)
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      Post-learning reflection

      Please take a moment to answer these post-learning questions.  These answers will be logged alongside your pre-learning responses on your CPD certificate which will be emailed to you on completion as evidence of your learning.



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      References and further reading

      1. NICE (2016) Head lice: Clinical Knowledge Summary. Available at: https://cks.nice.org.uk/head-lice#!topicsummary.

      2. GHURYE R (2018) Human head lice: Microanatomy and newer treatments. British Journal of Family Medicine. March 2018. Available at: https://www.bjfm.co.uk/human-head-lice-microanatomy-and-newer-treatments.

      3. PUBLIC HEALTH ENGLAND (2018) Health protection in schools and other childcare facilities. Available at: https://www.gov.uk/government/publications/health-protection-in-schools-and-other-childcare-facilities/chapter-9-managing-specific-infectious-diseases.

      4. MHRA (2018) Head lice eradication products: Risk of serious burns if treated hair is exposed to open flames or other sources of ignition, e.g. cigarettes. Available at: https://www.gov.uk/drug-safety-update/head-lice-eradication-products-risk-of-serious-burns-if-treated-hair-is-exposed-to-open-flames-or-other-sources-of-ignition-eg-cigarettes

       

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