What are the treatment options for lice infestation?

Treatment Options for Lice Infestation

Permethrin 1% lotion is the recommended first-line treatment for head lice due to its effectiveness and safety profile, applied to damp hair for 10 minutes and repeated in 7-10 days to kill newly hatched nymphs. 1

First-Line Treatment: Permethrin 1%

• Permethrin 1% is a cream rinse applied to hair that has been shampooed with a non-conditioning shampoo and towel dried 2
• Leave on for 10 minutes, then rinse off; the residue helps kill nymphs emerging from eggs not killed in the first application 1
• Has low mammalian toxicity and does not cause allergic reactions in patients with plant allergies 2, 1
• A second application is recommended 7-10 days after the first to kill newly emerged nymphs 1
• Conditioners and silicone-based additives in shampoos can impair permethrin adherence to the hair shaft and reduce its effectiveness 2
• Resistance to permethrin has been reported, though prevalence is unknown 2, 1

Second-Line Treatment: Pyrethrins Plus Piperonyl Butoxide

• Neurotoxic to lice with extremely low mammalian toxicity 2
• Applied to dry hair and rinsed out after 10 minutes 2
• Should be avoided in patients allergic to chrysanthemums 2
• 20-30% of eggs remain viable after treatment, requiring a second treatment in 7-10 days 2
• Resistance has been reported in some cases 2, 3

Third-Line Treatment: Malathion 0.5%

• Indicated when resistance to permethrin or pyrethrins is documented or when first-line treatments fail despite correct use 2, 1
• Applied to hair, left to air dry, then washed off after 8-12 hours 2
• Has high ovicidal activity but requires reapplication if live lice are seen in 7-10 days 2
• Highly flammable due to high alcohol content; risk of severe respiratory depression if ingested 2, 4
• Should not be exposed to open flames or electric heat sources, including hair dryers and electric curlers 4

Fourth-Line Treatment: Lindane 1%

• Not recommended as a first-line treatment due to safety concerns 1
• Should be left on for no more than 10 minutes with a second application in 7-10 days 2
• Has low ovicidal activity and resistance has been reported worldwide 2
• Only available by prescription and should be used cautiously due to risk of seizures in children 2
• Should only be used for patients who cannot tolerate or whose infestation has failed to respond to safer medications 1

Alternative Treatments

• Oral ivermectin can be used as an alternative treatment (200 mg/kg, repeated in 10 days) 1, 5
• Should not be used for children who weigh less than 15 kg due to risk of crossing blood-brain barrier 1

Adjunctive Measures

• All household members should be checked for lice, and only those with live lice or eggs within 1 cm of scalp should be treated 2, 6
• Siblings who share a bed with an infested person should be treated even if no live lice are found 6
• Vinegar or vinegar-based products can be applied to hair for 3 minutes before combing to help loosen nits 2, 1
• Clean hair care items and bedding used by the infested person 6
• Disinfect hats, hair ribbons, scarves, coats, towels, and bed linens by machine washing in hot water (above 54°C/130°F) and using the hottest dryer setting for at least 20 minutes 7

Common Pitfalls and Considerations

• Never initiate treatment without a clear diagnosis of head lice 2
• Treatment failure often results from improper application rather than resistance 6
• Itching or mild burning of scalp after treatment is common; topical corticosteroids and oral antihistamines may help relieve post-treatment inflammation 2, 1
• Misdiagnosis of dandruff or hair casts as nits is common; confirm diagnosis by finding live lice 6
• For persistent cases, consider misdiagnosis, non-adherence to treatment protocol, reinfestation, or resistance 2