What is the treatment for pediculosis (lice infestation)?

Treatment of Pediculosis (Lice Infestation)

Immediate Treatment Recommendation

For head lice, apply permethrin 1% lotion to damp, towel-dried hair for 10 minutes, then rinse, and repeat in 7-10 days; for pubic lice, apply permethrin 1% cream rinse to affected areas for 10 minutes; for body lice, machine wash all clothing and bedding in hot water, which is often sufficient without medication. 1, 2, 3

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Head Lice (Pediculosis Capitis) Treatment Algorithm

First-Line Treatment

• Permethrin 1% lotion is the recommended first-line agent due to its effectiveness and safety profile 1
• Apply to damp, shampooed hair (use non-conditioning shampoo) that has been towel-dried 1
• Leave on for 10 minutes, then rinse thoroughly over a sink with warm water to limit skin exposure 1
• Mandatory second application on day 7-10 is required because permethrin has only 70-80% ovicidal activity, meaning it doesn't kill all eggs 1
• Permethrin has low mammalian toxicity and does not cause allergic reactions in patients with plant allergies 1

When First-Line Treatment Fails

• Malathion 0.5% lotion is the second-line option when resistance to permethrin is documented or first-line treatment fails despite correct application 1, 4
• Malathion has the highest ovicidal activity but requires 8-12 hours of contact time 1
• Critical safety warning: Malathion is highly flammable due to alcohol content—no smoking, open flames, hair dryers, or electric curlers while hair is wet 1, 4
• Can cause severe respiratory depression if ingested and chemical burns including second-degree burns 4

Alternative Treatment

• Spinosad 0.9% topical suspension achieves high cure rates with a single 10-minute application to dry hair and scalp 1
• Oral ivermectin 200 mcg/kg, repeated in 10 days, but should not be used in children weighing less than 15 kg due to blood-brain barrier penetration risk 1

Treatments to Avoid

• Lindane 1% is not recommended as first-line treatment due to low ovicidal activity (30-50% of eggs survive), widespread resistance, and seizure risk 1
• Use lindane only when patients cannot tolerate or have failed safer medications 1

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Pubic Lice (Pediculosis Pubis) Treatment

Recommended Regimens

• Permethrin 1% cream rinse applied to affected areas and washed off after 10 minutes 2
• Alternative: Pyrethrins with piperonyl butoxide applied to affected areas and washed off after 10 minutes 2
• Lindane 1% shampoo applied for 4 minutes then thoroughly washed off, but not recommended for pregnant/lactating women or children under 2 years 2

Special Considerations

• Do not apply to eyes; for eyelash pediculosis, apply occlusive ophthalmic ointment to eyelid margins twice daily for 10 days 2
• Evaluate for other sexually transmitted infections when pubic lice are found 5, 6
• Re-evaluate after 1 week if symptoms persist; re-treatment may be necessary if live lice or eggs at hair-skin junction are observed 2

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Body Lice (Pediculosis Corporis) Treatment

Environmental Measures (Often Sufficient Alone)

• Machine wash all infested clothing, bedding, and linens in hot water and dry using hot cycle, or dry-clean them 3
• This is the cornerstone of treatment and often sufficient without medication 3
• Remove items from body contact for at least 72 hours if washing is not immediately possible 3
• Fumigation of living areas is not necessary 3

Medical Treatment (When Needed)

• Permethrin 1% cream rinse applied to affected body areas and washed off after 10 minutes 3
• Alternative: Pyrethrins with piperonyl butoxide applied to affected areas and washed off after 10 minutes 3
• Lindane 1% lotion can be applied thinly from neck down and washed off after 8 hours, but avoid in pregnant/lactating women and children under 2 years 3

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Critical Management Points for All Types

Contact Management

• Examine all household members; only treat those with live lice or eggs within 1 cm of scalp 1
• Treat sex partners within the preceding month for pubic lice 2
• Treat family members who share a bed with infected person 5

Environmental Decontamination

• Machine wash and dry hair care items and bedding in hot water 5
• Remove items from body contact for at least 72 hours if washing not possible 2, 3
• Fumigation is not necessary 2, 3

Common Pitfalls to Avoid

• Post-treatment itching persists for days and is not treatment failure—it represents an allergic reaction to dead lice 1
• Topical corticosteroids and oral antihistamines may relieve post-treatment inflammation 1
• Consider improper application as the first cause of treatment failure before assuming resistance 1
• Vinegar or vinegar-based products can be applied to hair for 3 minutes before combing to help loosen nits 1

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Special Populations

Pregnancy and Lactation

• Use permethrin or pyrethrins with piperonyl butoxide only—avoid lindane 2, 3
• Permethrin is safe for pregnant and breastfeeding women 7

Children

• Permethrin is safe for infants and young children 7
• Lindane should not be used in children under 2 years 2, 3
• Oral ivermectin should not be used in children weighing less than 15 kg 1
• Malathion should only be used under direct adult supervision 4

HIV-Infected Patients

• Treat with the same regimens as HIV-negative patients 2