Testing overview

  • inspection
    • wet and comb hair, remove tangles
    • examine under strong light with magnifying glass
    • use fine-toothed comb (teeth 0.2 to 0.3 mm apart)
    • insert comb near crown at scalp
    • comb entire head systematically at least twice
    • examine comb after each stroke

Treatment overview

  • topical procedures
    • optimal pediculicide dependent on local resistance patterns
    • universal retreatment recommended in 7 to 10 days if live lice seen
    • permethrin 1% applied to towel-dried hair, leave for 10 minutes then rinse
      • FDA approved in adults and children ≥2 months old
      • recommended by AAP as treatment of choice for head lice
    • malathion 0.5% lotion applied to dry hair, then after 8 to 10 hours washed off with shampoo
      • FDA approved in adults and children ≥6 years old
      • recommended when permethrin resistance suspected
    • benzyl alcohol lotion 5% lotion applied for 10 minutes
      • FDA approved in patients ≥6 months old
    • ivermectin 0.5% lotion applied to dry hair for 10 minutes
      • FDA approved in patients ≥6 months old
    • other topical treatments
      • dimethicone 4% lotion
      • spinosad 0.9% topical suspension (FDA approved in patients ≥4 years old)
      • pyrethrins with piperonyl butoxide applied to dry hair for 10 minutes
      • lindane no longer recommended for use as pediculicide
  • occlusive agents may be effective including
    • melaleuca plus lavender oil
    • coconut plus anise oil
    • petroleum jelly
  • nit removal
    • evidence limited and inconsistent
    • nit-removal combs do not appear to be effective adjunct to topical pediculicide
    • “no-nit” policies for return to school
      • discouraged by AAP and APHA
      • may be required for reentry to school or day care based on local regulations
  • oral medications
    • not approved by FDA for treatment of head lice
    • options may include
      • trimethoprim-sulfamethoxazole 5 mg/kg twice daily
      • oral ivermectin 400 mcg/kg twice 7 days apart
      • pediculicide considered effective if lice dead or slowly moving 8 to 12 hours after treatment

Other management

  • physical nit removal (evidence for effectiveness limited and inconsistent)
  • nit-removal combs do not appear to be effective adjunct to topical pediculicide


  • blowing hot air through custom-built hair dryer for 30 minutes reported effective
  • desiccation with regular blow-dryer not recommended (due to potential spread)

Treatments not recommended

  • head shaving (effective but distressing)
  • flammable or toxic substances such as gasoline or kerosene products
  • nit-loosening agents (such as vinegar, vinegar-based products, acetone, bleach, vodka, and WD-40)
  • topical spray (dyes nits bright pink)


  • confirm treatment success 1 to 2 days after final application of pediculicide
    • if moving lice of all sizes present, resistance
    • if only 1 adult-size louse present, re-infestation
  • re-treat with different pediculicide if re-infestation occurs within 1 month

Causes of treatment failure

  • misunderstanding/noncompliance instructions
  • inappropriate instructions from product/clinician
  • misdiagnosis
  • inappropriate product used
  • failure to re-treat recommended interval
  • live eggs not removed
  • acquired resistance to pediculicide
  • treatments to consider if proven resistance or active infestation documented include
    • benzyl alcohol 5% of age > 6 months
    • malathion 0.5% if age >24 months
    • manual removal via wet combing or occlusive method (such as petroleum jelly or suffocation product) for younger patients, with 2 to 4 treatment cycles


  • secondary bacterial skin infection due to scratching (rare)


  • pruritus may persist 7 to 10 days after effective treatment
  • current resistance rated unknown
  • most children with nits but no active lice do not develop lice
  • re-infestation may be common

Contacts of index cases

  • screen all household members
  • treat if live lice or nits identified within 1 cm of scalp
  • consider treating family members who share a bed with index case even if no live lice found

School attendance

  • do not restrict children from school due to lie, due to low risk of contagion within classrooms

Dr. Drabkin is a senior clinical writer for DynaMed (www.ebscohost. com/dynamed), a database of comprehensive updated summaries covering more than 3,200 clinical topics, and assistant clinical professor of population medicine at Harvard Medical School.

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