What is the recommended treatment for a patient with a lice infestation?

Head Lice Treatment

First-Line Treatment: Permethrin 1%

Permethrin 1% cream rinse is the recommended first-line treatment for head lice, applied to damp hair for exactly 10 minutes, with a mandatory second application 7-10 days later. 1, 2, 3

Application Technique

• Wash hair first with a non-conditioning shampoo (conditioning products prevent proper adherence) 1, 2
• Towel dry until damp, not soaking wet 1, 3
• Apply permethrin 1% cream rinse thoroughly to the scalp, hairline, neck, temple, and forehead 1
• Leave on for exactly 10 minutes—not longer or shorter 1
• Rinse over a sink with warm water (not hot water, to minimize absorption) 1, 2
• Second application on day 7-10 is mandatory because permethrin has only 70-80% ovicidal activity 1, 2

Special Populations

• Safe for children and has low mammalian toxicity 2, 3
• Does not cause allergic reactions in patients with plant allergies 2, 3
• In infants and elderly patients, pay special attention to scalp, hairline, neck, temple, and forehead as these areas are more commonly infested 1

Alternative First-Line: Pyrethrins with Piperonyl Butoxide

• Apply to dry hair for 10 minutes, then rinse 3, 4
• Requires second application in 7-10 days 4
• Allow product to remain for 10 minutes but no longer 4
• Use warm water to form lather, shampoo, then thoroughly rinse 4

Second-Line Treatment: Malathion 0.5%

Switch to malathion 0.5% if live lice are confirmed 7-10 days after a second properly applied permethrin treatment, indicating likely resistance. 2

Application Protocol

• Apply to dry hair and allow to air dry naturally 2, 3
• Leave on for 8-12 hours 2, 3
• Has the highest ovicidal activity (approximately 98%) of all treatments, often requiring only a single application 2, 3
• Reapply in 7-9 days only if live lice are still present 2

Critical Safety Warning

• Contains 78% isopropyl alcohol, making it highly flammable 3
• Do not use near open flames, sparks, or heat sources 3
• Risk of severe respiratory depression if ingested 2
• Approved for children ≥6 months, contraindicated in children <24 months 2

Third-Line Options

Spinosad 0.9% Topical Suspension

• Apply to dry hair and scalp for 10 minutes, then rinse thoroughly 2
• Achieves high cure rates (75-85%) with a single 10-minute application 2

Benzyl Alcohol 5%

• Approved for children >6 months 2
• Kills lice by asphyxiation 2
• Requires repeat application in 7 days 2
• More than 75% of patients are lice-free 14 days after initial treatment 2

Topical Ivermectin 0.5% Lotion

• Single application achieves 73.8% cure rate at day 15 5
• Well tolerated with minimal adverse effects 5
• Reserved as third-line due to limited clinical experience and cost 5

Treatments to Avoid

Lindane 1% should NOT be used as first-line treatment due to severe safety concerns, including seizure risk and neurotoxicity. 2, 3

• Only use when all other treatments have failed 2
• Has low ovicidal activity (30-50% of eggs not killed) 2
• Widespread resistance documented 2

Critical Management Points

Who to Treat

• Only treat individuals with live lice or nits within 1 cm of the scalp 2, 3
• Examine all household members with magnifying glass in bright light 4
• Treat family members who share a bed with infected person 3, 4

Post-Treatment Expectations

• Itching after treatment is normal and NOT a sign of treatment failure 1, 2, 3
• Post-treatment pruritus is an inflammatory response that can persist for many days 1, 2
• Only retreat if live lice are seen 7-10 days after treatment, not based on itching alone 1, 2, 3
• Topical corticosteroids and oral antihistamines may help relieve post-treatment inflammation 2, 3

Environmental Decontamination

• Wash all clothing, bedding, and linens in hot water (above 54°C/130°F) and dry on hot cycle on the same day as treatment 1, 3, 4
• Wash hair care items (combs, brushes) in hot water above 54°C for at least 10 minutes 1, 4
• Remove items that cannot be washed from body contact for at least 72 hours (lice cannot survive off human body for more than 2-3 days) 1, 3
• Vacuum carpets, mattresses, upholstered furniture, and car seats 4
• Fumigation of living areas is NOT necessary 1

Nit Removal (Optional)

• Vinegar or vinegar-based products can be applied to hair for 3 minutes before combing to help loosen nits 2, 3
• Use fine-tooth nit comb on damp hair 2, 4
• Nit removal is not necessary to prevent spread but can help decrease diagnostic confusion 3

Common Pitfalls to Avoid

• Do NOT use conditioning shampoo before applying permethrin—it prevents proper adherence 1, 2
• Do NOT skip the second application for permethrin or pyrethrins—it is mandatory due to incomplete egg kill 1, 2
• Do NOT retreat based on itching alone—consider improper application as the first cause of treatment failure before assuming resistance 1, 2, 3
• Do NOT rinse with hot water—use warm water to minimize absorption 1, 2
• Most "resistance" is actually due to improper application, misdiagnosis, noncompliance, or reinfestation 2, 3