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Head lice: rid the kids of that common itch

Rupal Shah

Head lice (pediculosis capitis) are most common in children aged between 4 and 11 years old, with girls being affected more often than boys. Eggs take approximately seven days to hatch, after which the lice take 9-12 days to mature and live for about 20 days altogether.
"Nits" are the empty eggshells that are left behind. Their presence is not enough to confirm infestation; a live louse is required for this. Transmission occurs through close head-to-head contact. Lice cannot survive long without a live host and do not remain on pillow cases or clothes. Therefore these items do not have to be washed specially. There is generally a delay of a few weeks before a diagnosis of lice is made, so keeping an affected child off school is unnecessary as transmission is likely to have occurred already.
Itching is common but not inevitable. Patients often have papules on the nape of the neck, and nits may be found above the ears or around the hairline. Secondary bacterial infection can occur, and patients who present with scalp impetigo should be examined for head lice.


Lotions are the formulation of choice as they are most effective and are less likely to encourage resistance. Those with an aqueous base are preferred as alcohol-based preparations are more likely to irritate the scalp.
Local resistance patterns should influence prescribing, and if treatment fails a different class of insecticide should be used next time so that resistance does not occur. Permethrin and phenothrin are from the same class.
Most evidence exists for malathion and permethrin, both of which are available over the counter. Treatment should usually be repeated within 7-10 days, to kill any newly hatched lice.
Other family members should be examined and treated as appropriate. A Cochrane review found no evidence of harm from treatment with malathion, permethrin or phenothrin.(1)

Malathion has been found to be more effective than placebo or wet combing with conditioner at
eradicating lice.(1) It is also likely to compare favourably with phenothrin lotion.(2)

Permethrin has also been found to be more effective than placebo.(1)

Phenothrin has been shown to be marginally more effective than dimeticone.(3)

There are no high-quality trials examining the effectiveness of carbaryl. It is only available on prescription. Resistance rates are thought to be low.


This involves shampooing the hair, applying conditioner and then using a fine-tooth comb to remove the lice. It needs to be repeated every four days for at least two weeks, until no lice are seen on three consecutive sessions.(4)

Dimeticone lotion
Dimeticone is a new, insecticide-free lotion that can be used to treat head lice. In a recent trial,(3) 214 children and 39 adults with active infestation were randomised to receive two applications of 4% dimeticone lotion (seven days apart and applied for 12 hours or overnight) or 0.5% phenothrin liquid. Cure was achieved in 70% of people treated with dimeticone, compared with 75% of those treated with phenothrin. Dimeticone was found to be less of an irritant than phenothrin and has the advantage of not producing resistance.

Natural oils
These include tea tree, lavender and neem. It is not clear how effective these preparations are.

This article has been supplied by the Royal College of General Practitioners and published with their kind


  1. Dodd CS. Interventions for treating head lice. The Cochrane Library. Issue 4. Oxford: Update Software; 2003.
  2. Chosidow O, Chastang C, Brue C, et al. Controlled study of malathion and d-phenothrin lotions for Pediculus humanus var capitis-infested schoolchildren. Lancet 1994;344:1724-7.
  3. Burgess I, Brown C, Lee P. Treatment of head louse infestation with 4% dimeticone lotion: randomised controlled equivalence trial. BMJ 2005;330:1423-5.