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There are now many treatments available for head lice, but which ones work? In the third of our series on minor ailments, where experts give an evidence-based update on what works, Dr Ciara Dodd and Mr Ian Burgess offer advice
Infection with head lice can be a problematic and confusing experience for sufferers and their families for a number of reasons:
• A wide variety of treatment options are readily available over the counter, including conventional pediculicides and herbal or other alternative remedies.
• Treatment failure can occur due to inappropriate application of the product, less effective formulations or because of insecticide resistance.
• Patients often do not know where to go for information about treatment options, particularly after treatment failure, and many people are concerned about toxicity of insecticides.
• Diagnosis can be poor, and many misconceptions about head lice are still widely believed which may lead to inappropriate treatment, so patients suffer head lice for longer than necessary.
• Evidence of the effectiveness of treatments from high-quality clinical trials is limited, particularly for alternative therapies.
Two systematic reviews1,2 and two evidence-based reviews3,4 have been conducted of randomised controlled trials for head louse treatments. Although the assessment of methodological quality of these reviews differs, all agree that the number of quality trials in this area is limited. To date 74 studies have been reviewed, of which 13 are considered of acceptable quality. The major conclusions of these reviews are summarised (see table).
• Combing with a plastic detection comb with or without conditioner is the best method for detecting louse infestation3.
• Traditional chemical treatments have all shown successful outcomes, but individual treatment failures may result from insecticide resistance, inadequate or incorrect application.
What doesn't work?
• Evidence for the effectiveness of herbal treatments or essential oils is lacking. Tea tree oil can kill lice if used in a high enough dose but these oils can be extremely damaging to hair and can cause skin irritant or hypersensitivity. Some are downright dangerous. There is no scientific evidence that neem has an effect on lice. Vinegar and lemon juice are old wives' tales.
• There is widespread evidence of resistance to pyrethroid-based products in many countries, although they remain useful in many circumstances. Evidence of resistance to malathion has also been documented5,6.
• There is insufficient evidence to determine whether combing as a treatment is as effective as chemical interventions, but it may prove useful in some cases.
• There is no published evidence to indicate the effectiveness of other electrical and/or mechanical devices such as combs, vacuum cleaners etc.
The bottom line: what GPs should do
A typical approach to treating a head louse infection based on the currently available evidence suggests:
1 Accurate diagnosis is the most important factor in developing an effective treatment strategy.
2 Treatment should only be given if live lice are found. Eggs or nits alone are not sufficient evidence of an active infection.
3 Preferred treatment should depend on patient reports of successful or unsuccessful past treatments, as resistance patterns will change over time.
4 In line with BNF recommendations a second treatment should be given after seven days.
5 Many treatments are unsuccessful as insufficient product is prescribed (the 50ml bottle is too small to treat long thick hair).
6 If treatment fails after 14 days a different insecticide or treatment strategy (eg wet combing) should be used.
7 The effectiveness of herbal therapies has not been proved and should be used with caution (there are currently no licensed products in the UK).
8 Combing can be effective using plastic detection combs, but users must be prepared to commit considerable time and continuous combing episodes over several weeks may be required to achieve cure.
Ciara Dodd is a biologist at the University of Cardiff, and Ian Burgess is consultant medical entomologist – both are members of the Cochrane Infectious Diseases Group
Systematic and evidence-based reviews of head louse treatment
Bottom line conclusion
Most randomised trials of head louse treatments are not of high quality (total of 74 studies reviewed)
Malathion treatments are more effective than phenothrin, wet combing with conditioner and placebo (three trials)
Permethrin is more effective than pyrethrin, lindane or placebo (seven trials)
Evidence about the effectiveness of herbal therapies is lacking (one trial)
Combing as a treatment is equivalent or less effective than chemical treatment (three trials)
61 studies classified as low quality, and 13 trials as acceptable quality
On average 87% of patients treated with malathion were cured compared with 52% receiving other treatments
On average 97% of patients treated with permethrin were cured compared with 64% receiving other treatments
No significant difference was detected between the effectiveness of treatments
Pediculicide application plus combing cured on average 63% of patients compared with 46% receiving no combing; combing without chemical treatment cured 38% of patients compared with
78% who received only chemical treatment
Head lice: evidence for effectiveness of herbal treatments or essential oils is lacking
1 Vander Stichele RH. Systematic review of clinical efficacy of topical treatments for head lice. BMJ 1995; 311: 604-608
2 Dodd CS. Treatment of Head Lice (Cochrane Review). In: The Cochrane Library, Issue 3, 2004. Oxford: Update Software
3 Burgess IF, Dodd CS. Head Lice. In: Evidence-based Dermatology. Eds. Williams H, Bigby M, Diepgen T, Herxheimer A, Naldi L, Rzany B. 2003; pp. 525-532
4 Burgess IF. Head Lice. In: Clinical Evidence. 2004. London BMJ Publications
5 Downs AMR et al. Evidence for double resistance to permethrin and malathion in
head lice. British Journal of Dermatology 1999; 141: 508-511
6 Burgess IF, Brown CM. Management of insecticide resistance in head lice Pediculus capitis (Anoplura: Pediculicidae). 1999.In: Proceedings of the 3rd International Conference on Urban Pests. Eds. Robinson RM, Rettich F, Rambo GW. Pp. 249-254