BMJ  2005;331:362-363 (13 August), doi:10.1136/bmj.331.7513.362

Editorial

Combing and combating head lice

Choose between four successive combings or two applications of pediculicide

You have to take your hat off to the head louse. Described in ancient Egyptian and Greek medical texts, it has been a source of irritation and disgust for thousands of years. Today, with a search on Google yielding 699 000 hits, the mostly harmless head louse has developed into an apparently fearsome pest. During the past 2000 years, a wide range of treatments for head louse infestation has been proposed. Not one has worked sufficiently for it to be regarded as a panacea. The comparison of effectiveness of comb and pediculicide, as reported in a paper in this week's BMJ, is certainly not new.¹

Hill et al (p 384) report this week the most complete assessment of the non pharmacological approach "Bug Buster," testing it against pediculicides available over the counter in the United Kingdom.² This paper is particularly relevant and timely in the northern hemisphere because the school year starts again in a few weeks' time and, once again, health professionals are going to be asked for advice on the "best" treatment.

This paper by Hill et al seems to show that Bug Buster—a kit comprising four fine-toothed combs with instruction to use them with conditioner four times over two weeks—is more effective in eradicating infestation than a single treatment of a pediculicide available over the counter (malathion or permethrin) with cure rates of 57% versus 13%. The cure rate for treatment with pediculicides is surprisingly low compared with rates in other trials (generally in the range 70-80%).^{3 4} Why was treatment with the pediculicides in this trial so much less effective than in other studies?⁵ For example, a recent trial in the BMJ by Burgess et al testing phenophrin against dimethicone found cure rates of 75% and 70%, respectively.⁶

The participants in both studies were children and young adults.^{2 6} They responded to advertisements in the press to take part in the trial by Burgess and colleagues, whereas in the trial by Hill et al they were asked by their general practitioners to participate or responded to posters and information sheets in local pharmacies and primary schools. These different methods of recruitment may have yielded different types of participant.

The general practitioners recruiting patients in the Bug Buster trial were all given the randomisation list and could see, therefore, who would be allocated to which treatment before even talking to each patient about joining the study. The selection bias that could have arisen from this might, in turn, have led to as much as a 30% increase in the apparent efficacy of bug busting⁷ compared with a trial with adequate concealment of randomisation. It is also possible that, despite using the randomisation list, some general practitioners used only one form of treatment because the number of patients recruited in some regions was very low. This additional bias might have been avoided by using block randomisation.

Lastly, the trial by Hill et al may have used inadequate doses of pediculicide. The authors acknowledge that using only a single dose may have led to failed treatment. The British National Formulary recommends two doses, stating that "permethrin is active against head lice but the formulation and licensed methods of application of the current products make them unsuitable for the treatment of head lice." In the trial by Burgess et al participants used double doses of phenophrin and dimethicone.⁶ Furthermore, the paper by Hill et al does not mention the duration of the infestation; the length, thickness or oiliness of the hair; and most importantly the intensity of the infestation—it simply states that participants had to have "a live head louse."

I am now thoroughly confused but better informed. Possible explanations for the large effect size of bug busting and the smaller effect of pediculicide in the study by Hill et al are that the results are true, the results are due to chance, or the study was biased against treatment with pediculocide. Despite these reservations, this paper confirms that bug busting, in the right hands, seems to be very effective. Indeed, from previous evidence it looks like bug busting treatment is probably as effective as pediculicide treatment applied twice.

Department of Family Medicine, McGill University, 515 Avenue des Pins, Montreal, Quebec H2W1S4 Canada
(martin.dawes{at}mcgill.ca)

---

Primary care p 384

Competing interests: MD has taken part in a pharmaceutical sponsored national committee to develop educational materials covering the management of head louse infestation.

References

1. Auden GA. The problem of the head louse. Lancet 1921;198: 370-2.[CrossRef]
2. Hill N, Moor G, Cameron MM, Butlin A, Preston S, Williamson MS, Bass C. Single blind, randomised, comparative study of the Bug Buster kit and over the counter pediculicide treatments against head lice in the United Kingdom. BMJ 2005;331: 384-6.[Abstract/Free Full Text]
3. Vander Stichele RH, Dezeure EM, Bogaert MG. Systematic review of clinical efficacy of topical treatments for head lice. BMJ 1995;311: 604-8.[Abstract/Free Full Text]
4. Dodd CS. Interventions for treating headlice. Cochrane Database Syst Rev 2001;(3): CD001165.
5. Nash B. Treating head lice. BMJ 2003;326: 1256-7.[Free Full Text]
6. Burgess IF, Brown CM, Lee PN. Treatment of head louse infestation with 4% dimeticone lotion: randomised controlled equivalence trial. BMJ 2005;330: 1423.[Abstract/Free Full Text]
7. Juni P, Altman DG, Egger M. Assessing the quality of controlled clinical trials. BMJ 2001;323: 42-6.[Free Full Text]

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