What is the recommended treatment for lice infestation?

Treatment of Head Lice (Pediculosis Capitis)

Permethrin 1% lotion is the recommended first-line treatment for head lice, applied to damp, shampooed hair for 10 minutes, then rinsed off, with a second application in 7-10 days. 1

First-Line Treatment: Permethrin 1%

• Apply permethrin 1% cream rinse to hair that has been shampooed with a non-conditioning shampoo and towel-dried 2
• Leave on for 10 minutes, then rinse thoroughly 2, 1
• Repeat application in 7-10 days (preferably day 9) to kill newly hatched nymphs from eggs that survived the first treatment 2, 1
• Permethrin has low mammalian toxicity and does not cause allergic reactions in patients with plant allergies 2, 1
• Clinical trials demonstrate 96-99% cure rates at 14 days with permethrin, significantly superior to other treatments 3, 4

Important Considerations for Permethrin

• Modern shampoos contain conditioners and silicone-based additives that impair permethrin adherence to hair shafts, reducing residual effect 2
• Many experts now recommend routine re-treatment on day 9 even if no live lice are visible 2
• Resistance to permethrin has been reported, but prevalence is unknown 2, 1
• Before assuming resistance, consider improper application as the most common cause of treatment failure 1

Second-Line Treatment: Malathion 0.5%

• Use malathion 0.5% when resistance to permethrin is documented or when first-line treatment fails despite correct application 2, 1
• Apply to dry hair, allow to air dry naturally, then wash off after 8-12 hours 5
• Has high ovicidal activity; single application is adequate for most patients 2
• Repeat in 7-9 days if live lice are still present 5
• Only approved for children 24 months of age or older 2

Critical Safety Warnings for Malathion

• Malathion is highly flammable due to high alcohol content—do not expose to open flames, electric heat sources, hair dryers, or smoking 2, 5
• Risk of severe respiratory depression if ingested 2
• Must be used under direct adult supervision in children 5

Alternative Treatments

Pyrethrins Plus Piperonyl Butoxide

• Apply to dry hair and rinse after 10 minutes 2
• Has extremely low mammalian toxicity 2
• Avoid in patients allergic to chrysanthemums 2
• 20-30% of eggs remain viable after treatment, requiring second application in 7-10 days 2
• Resistance has been reported 2

Oral Ivermectin

• Single dose of 200 mcg/kg, repeated in 10 days 1
• Should not be used in children weighing less than 15 kg due to risk of crossing blood-brain barrier 1
• Not FDA-approved as a pediculicide 2

Treatments to Avoid

Lindane 1%

• Should NOT be used as first-line treatment due to safety concerns 1
• Only for patients who cannot tolerate or have failed safer medications 1
• Low ovicidal activity (30-50% of eggs survive) 1
• Risk of seizures in children—use with extreme caution 2
• Resistance reported worldwide 2

Household Management

• Examine all household members; treat only those with live lice or eggs within 1 cm of scalp 2, 1
• Treat family members who share a bed with the infested person 2
• Clean hair care items and bedding 2
• Machine wash infested items in hot water and dry on hot cycle 6

Nit Removal

• Nit removal after treatment is NOT necessary to prevent spread 2
• Recommended for aesthetic reasons or to decrease diagnostic confusion 2
• Apply vinegar or vinegar-based products to hair for 3 minutes before combing to help loosen nits 2, 1

Common Pitfalls to Avoid

• Never initiate treatment without confirmed diagnosis of live lice 2, 1
• Misdiagnosis is a common cause of perceived treatment failure 2
• Noncompliance with treatment protocol (incorrect application time, not repeating treatment) 2
• Reinfestation from untreated household contacts 2
• Itching after treatment is common and NOT a reason for re-treatment—consider topical corticosteroids or oral antihistamines for post-treatment inflammation 2, 1

School Attendance

• Children should remain in school and not miss valuable school time due to head lice 2
• The child has likely had the infestation for a month or more by the time discovered and poses little risk to others 2
• Allow return to school after proper treatment 2
• Head lice screening programs are not cost-effective and have not reduced incidence over time 2