While current prevalence data is very limited, NICE's Clinical Knowledge Summaries (CKS) guidance for head lice says infestation is most common in the 4-11 years age group, peaking at age 7-8; girls are more likely to catch head lice than boys.3

Treatment recommendations rely on a live louse being found. Three approaches are given in the CKS guidance:3

·      physical insecticides: dimeticone, or isopropyl myristate combined with cyclomethicone or isopropyl alcohol;

·      chemical insecticides: only malathion 0.5% aqueous liquid (Derbac-M) is recommended, but resistance has been reported;

·      wet combing with a fine-tooth comb.

Neither NHS Choices nor NHS Inform refer to malathion.19,20 Permethrin is no longer recommended, due to questions over effectiveness and resistance.3

Also specifically not recommended by NICE are phenothryn or carbaryl, which are no longer available in the UK, and Hedrin Treat & Go (octane-1,2-diol) as it is not listed in the Drug Tariff (other head lice preparations including other Hedrin products are listed in Part IX A).3

In addition, the CKS guidance says the following should not be recommended due to a lack of supporting evidence for their safety and efficacy:

·      essential oil-based treatments such as tea tree or eucalyptus oil

·      herbal remedies

·      electric combs (due to expense and potentially a safety risk if not used correctly)

·      Nitlotion or Lice Attack shampoo (both based on coconut oil)

·      Dove hair conditioner.

Parents should avoid using products marketed as head lice repellents, and should avoid the repeated use of treatments if no live lice have been detected.

Standard practice has been to apply the treatment twice, seven days apart to catch any new lice that may have hatched. However, Community Hygiene Concern points out:21

·      while head lice usually hatch 7 to 10 days after the eggs were laid, they can hatch from day 5 to 11

·      females can start laying eggs 7 days after hatching.

Therefore, to prevent head lice from spreading, live head lice must be eradicated before the sixth day after hatching. CHC advises to check for live head lice on days 5, 9, and 12/13 after the initial treatment and remove any.21 The UK Medicines Information (UKMi) group recommends detection combing on days 2-3 and 9-10 after the second application for further assurance.3 A 2014 study has also suggested that lice eggs can hatch as late as 13 days after the first treatment in a very small number of cases.22

Whether or not they have lice, CKS recommends that primary school children should be examined frequently (potentially weekly) at home to catch an infestation early.3