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. 2016 Apr;62(4):322.

The louse is (no longer) in the house

Michael R Kolber 1, Michael Pierse 2, Tony Nickonchuk 3
PMCID: PMC4830656  PMID: 27076544

Clinical question

What is the best treatment for head lice?

Bottom line

Dimeticone appears superior to traditional lice treatments, ridding 1 more in every 3 to 4 patients of lice with no increased adverse events. Dimeticone is a silicone-based product that suffocates lice.

Evidence

Trials found the following statistically significant results.

  • Two RCTs compared dimeticone with permethrin.
    • -A British RCT of 90 patients (aged 2 to 45)1 compared 4% dimeticone once with 1% permethrin twice (1 week apart) and found more dimeticone patients were lice free at day 9 (80% vs 36%, number needed to treat [NNT] = 3). Adverse events were similar and none were serious.
    • -A Brazilian RCT of 145 children (aged 5 to 15)2 compared 2 applications (1 week apart) of 92% dimeticone with 1% permethrin and found that more dimeticone patients were lice free at day 9 (97% vs 68%, NNT = 4). Adverse events were 2 cases of ocular irritation from dimeticone.

  • A British RCT of 73 patients (aged 1 to 48)3 compared 2 applications (1 week apart) of 4% dimeticone with 0.5% malathion. Analysis (considering dropouts to have lice) found more dimeticone patients were lice free at day 9 (70% vs 33%, NNT = 3).

  • Other European dimeticone RCTs found cure rates of 83% to 92%4 and 70% in patients predominantly with long-standing lice and previous failed treatments.5

Context

  • Most lice in North America (99%) express genes associated with traditional pediculicide resistance.6

  • Dimeticone is a silicone-based product that acts as an occlusive to suffocate lice and is applied to dry hair and left for 8 hours. It is often repeated after 1 week.7 Other occlusive agents, such as isopropyl myristate, also appear more effective than traditional pediculicides.8

  • In one study, less than 20% of children with nits developed active lice.9

  • Wet combing is better than inspection for diagnosing lice.10

  • Head lice are primarily transmitted from head-to-head contact in play and sharing beds, and occasionally by sharing objects like hats and combs.11

  • To decrease reinfestation, wash clothes and linens used 2 days previously in hot water and dry with high heat. Put unwashable items in a sealed bag for 2 weeks.12,13

  • Lice treatments cost about $30 and most are covered by drug plans.14

Implementation

Head lice are present throughout the world irrespective of socioeconomic climates, hair length, or hair cleanliness.11,15 The typical presentation is scalp itch (often worse at night), but diagnosis should only be made by observing a living louse (normally within 4 mm of the scalp).13 Lice treatment failures might be owing to retreatment before 8 to 10 days (ie, before eggs hatch); hair conditioner use, which prevents head lice medicine from adhering; reinfestation from another close contact; or pediculicide resistance.13 If pediculicide resistance is suspected, try an alternative product. As only 20% of children with nits develop lice, no-nit school policies should be abolished.11

Tools for Practice articles in Canadian Family Physician (CFP) are adapted from articles published on the Alberta College of Family Physicians (ACFP) website, summarizing medical evidence with a focus on topical issues and practice-modifying information. The ACFP summaries and the series in CFP are coordinated by Dr G. Michael Allan, and the summaries are co-authored by at least 1 practising family physician and are peer reviewed. Feedback is welcome and can be sent to toolsforpractice@cfpc.ca. Archived articles are available on the ACFP website: www.acfp.ca.

Footnotes

Competing interests

The authors have no conflicts of interest to declare. Dr Kolber’s kids have had lice, Mr Nickonchuk’s kids have been spared (so far), and Dr Pierse’s lack of hair is a natural defence against infestation.

The opinions expressed in Tools for Practice articles are those of the authors and do not necessarily mirror the perspective and policy of the Alberta College of Family Physicians.

References

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