Intended for healthcare professionals

Clinical Review Evidence based case report

Treatment for head lice

BMJ 1999; 318 doi: (Published 06 February 1999) Cite this as: BMJ 1999;318:385
  1. M Dawes, general practitioner (martin.dawes{at},
  2. N R Hicks, general practitioner,
  3. M Fleminger, general practitioner,
  4. D Goldman, general practitioner,
  5. J Hamling, general practitioner,
  6. L J Hicks, general practitioner
  1. Hollow Way Medical Centre, Oxford OX4 2NJ
  1. Correspondence to: Dr Dawes
  • Accepted 2 September 1998

Christopher, my son, has been lost in many places. One of his local adventures was in Sainsbury's. On losing sight of my wife he went to a member of staff and stated that he was lost. He was asked what his mummy looked like. “She's the one with a scarf on her head because she's got nits.” We frequently face the problem of head lice in practice, but our practice team felt uncertain about the most effective treatment.

The question

The first step was to design an answerable question. This is the three step question described by Scott Richardson.1 It should contain the problem, the intervention, and the outcome. Our final question was “In children attending primary care with nits what is the most effective treatment for eradication?”

The search

I gathered evidence from several sources hoping to gain a consensus. I was looking mainly for well designed clinical trials. A good source of evidence of a therapeutic effect is a meta-analysis of randomised controlled trials. The Cochrane Library is one source of high quality meta-analyses. However, I do not have this in my surgery so I looked up head lice in the Oxford Textbook of Medicine.2 The section on head lice began by giving me quotes from Robert Burns. There was a description of the biology and clinical features of head lice. It said that head lice are resistant to chlorinated hydrocarbons and suggested the use of malathion. “More recently Permethrin has been shown to be equally effective without the potentially toxic side effects (CNS) of Malathion.” It suggested that all these treatments achieve 100% cure rates but gave no idea of where the evidence for these statements came from.

I next looked up head lice in the British National Formulary. This recommended using malathion or carbaryl lotion with a contact time of 12 hours or overnight.3 Carbaryl was stated to be a potential human carcinogen. Permethrin and phenothrin were listed as second choice, although it mentioned resistance to these two compounds. I then rang the NHS helpline, which gave me advice and the telephone number of the Medical Entomology Centre in Cambridge. The box summarises the centre's advice.

Medical Entomology Centre information on head lice

  • Permethrin has a lot of resistance and is almost useless in the United Kingdom4

  • Head lice are spread by symptomless carriers (often children under 4 and adults with immunity)

  • Head lice are associated with impetigo

  • Head lice should be treated to ensure eradication

  • Carbaryl is almost 100% effective but use malathion first

  • Secondary treatment within seven days is necessary to eradicate the lice. If left longer the remaining lice will be well enough developed to transfer to another host

  • There is no danger of neurotoxicity as the drugs cannot bind to neuroreceptors

  • 40 million doses have been given in the United Kingdom with no reported neurological side effects

We have Bandolier in the practice's coffee room so I looked up head lice in the index and found a clear summary of a review of the literature published in 1995. 5 6 Although carbaryl seemed most effective, the number of patients treated in the studies using this compound was a quarter of the number tested with permethrin. Therefore Bandolierfelt more confident about the results from permethrin than it did about carbaryl and hence named permethrin as first choice. The table summarises the recommendations from all the sources.

Recommendations for treatment of head lice by various sources

View this table:

I searched the Cochrane Libraryusing the term “head lice.” The search found one study in the Database of Abstracts of Reviews of Effectiveness under abstracts of quality assessed systematic reviews.7 This was a review of the same article as in Bandolier. One major criticism of the study was that the authors had found 11 unpublished trials comparing permethrin and malathion which were not reported in the paper because the authors did not accept the company's demands on confidentiality. There were also studies with longer follow up than the 14 days used in this study. The commentary stated that the published results might not accurately reflect all the available evidence.

I found no evidence in the CD Rom Best Evidence.8 To be complete and to ensure that nothing significant had been published since the 1995 meta-analysis I searched Medline from home. I put in the search term “head lice” and was presented with a list of related medical subject headings (MeSH) headings: pediculosis, scalp dermatoses, pyrethrins, lice, scalp, insecticides, pediculus, malathion, insecticides, botanical, and DDT. As I wanted to ensure that I missed no important articles I selected all the options as well as the text term.

This search revealed 19 278 articles. I limited this by selecting randomised controlled trials within the “publication type” box. I now had 135 articles. Starting with the current year I looked through 42 of these before I reached 1994. This took only a few minutes. I found no relevant studies so I went back to my original search and limited it to meta-analyses. This gave two articles, one of which was that appraised in the Cochrane Library and Bandolier. It was available in the local library. The other article was not about head lice.

Appraising the evidence

I used the JAMAguide on appraisal of a meta-analysis to assess the quality of the paper by Vander Stichele.9

Did the overview address a focused clinical question? Yes—clinical efficacy of topical treatments for head lice.

Were the criteria for article inclusion appropriate? Yes. They used the criteria used by the Cochrane Library. However, there were 11 small (n<74) unpublished studies that they did not include because of company demands on confidentiality. Seven studies were included in the analysis. This will be a possible source of bias of the final results.

Is it likely that relevant studies were missed? No. They used electronic searches followed by reference searching and personal communication with authors.

Was the validity of included studies appraised? Yes.

Was the assessment of the studies reproducible? The authors displayed the data collected for assessment of the 28 identified trials and showed why only seven were of acceptable quality.

Were the results similar from study to study? Yes. Cure rates were generally between 75% and 100%.

What are the results?Control treatments are very ineffective. More studies examined permethrin than other compounds therefore we can be more confident about its effectiveness.

How precise are the results? The number of well conducted studies is limited. The results of the meta-analysis are therefore imprecise and the authors suggest that further research is needed.

Can the results be applied to my patients? The authors' addresses suggested that many of the studies were done in other countries and there may be differences in resistance.

Are the benefits worth the harms and the costs? I was worried by the potential side effects of some of the drugs but that was not part of our search question. Perhaps when we have time we might look at that.

The bottom line

The Medical Entomology Centre, which deals with resistance, states that carbaryl is the only (nearly) 100% effective treatment in Britain. But this information is not published and I cannot check the validity. What is clear is that the problem is not being tackled consistently and the advice is conflicting.

So what should we do? There is no published evidence about local resistance despite this being such a common problem. I will advise permethrin first but explain the importance of using the lotion correctly and give a leaflet to back up my advice. If the nits are not eradicated by this treatment I will prescribe carbaryl. The British National Formulary was the most effective source of evidence for this problem. The only drawback is that it never cites the sources of evidence it uses.

Finally the practice should study what effect this evidence based approach has. If I do an audit of patients with head lice and see how many come back for carbaryl this will give us an idea of how successful, or unsuccessful, permethrin is in our population. In my family we used it with good effect.


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