Revision as of 20:38, 25 June 2019 by Rossdonaldson1 (talk | contribs) (Background)


Lice (electron microscope)
Adult body louse and head lice: female (left) and male (right).
  • Lice are small wingless insects, dorsoventrally flattened, with reduced or no eyes and enlarged tarsal claws for clinging[1]
  • Types
    • Pediculus humanus capitis
    • Hats/combs may act as fomites

Clinical Features

Heavily infested hair with Pediculus humanus capitis (arrow).
  • May see live mites or nits (egg sacks) on hair shaft close to scalp
  • May be asymptomatic or pruritic

Differential Diagnosis

Domestic U.S. Ectoparasites

See also travel-related skin conditions


  • Generally a clinical diagnosis


Over the Counter (OTC)

  • Permethrin 1% lotion shampoo (if >2 months old)[2]
    • Wash hair with non-conditioned shampoo
    • Apply Permethrin for 10 min and rinse
    • Repeat on day 9
  • Pyrethrin lotion
    • Apply to affected areas and wash off after 10 min
    • Repeat in 7 days
  • Dimethicone therapy
    • First, apply the product to dry hair, then wait 10 min. Next, with product still in the hair, separate hair into small sections and comb hair to remove lice and eggs. Use a lice comb to remove lice and their eggs from hair. Finally, shampoo hair thoroughly with regular shampoo and warm water. Repeat as needed.[3]


Reserved for failed OTC treatment

  • Spinosad 0.9% topical suspension (if >6 months old)
    • Apply to scalp and air and wash off after 10 min.
    • Repeat in 10 days
  • Malathion 0.5% lotion (if >6 years old)
    • Applied to affected areas and wash after 8 hrs
    • Repeat in 7 days
  • Benzyl Alcohol 5% lotion (> 6 months old)
    • Apply to dry hair and wash off after 10 min
    • Repeat in 7 days
  • Ivermectin 400mcg/kg PO
    • Once on day 1 THEN once in 7 days
    • Reserved for patients failing topical treatment
  • Lindane therapy
    • Only consider if patient has failed two prior prescription treatments
    • Avoid in children <50 kg due to seizure association

Eyelash Infestation

  • Apply ophthalmic petroleum jelly q12hrs x 10 days

Pediatrics <2yo

  • Wet combing is an alternative to medical therapy


  • Discharge
  • Children can return to school after first topical treatment has been applied
  • Instruct parents and all close contacts to wash clothing and bedding in hot soapy water to avoid disease spread

See Also


  2. Devore CD and Schutze G. Head Lice. Pediatrics. 2015; 135(5) e1355-e1365.
  3. Ihde ES, Boscamp JR, Loh JM, Rosen L. Safety and efficacy of a 100% dimethicone pediculocide in school-age children. BMC Pediatr. 2015;15:70.