What is the treatment for pediculosis (lice infestation)?

Treatment for Head Lice (Pediculosis)

Permethrin 1% is the first-line recommended treatment for head lice due to its efficacy and safety profile. 1

First-Line Treatment Options

Permethrin 1% Cream Rinse

• Apply to damp, shampooed, and towel-dried hair
• Leave on for 10 minutes before rinsing off
• Advantages: Low mammalian toxicity, no allergic reactions in people with plant allergies 2, 1
• Repeat application in 7-10 days if live lice are still present 2
• Effectiveness: 96% of patients remain lice-free at 14 days 3

Pyrethrins with Piperonyl Butoxide

• Apply to dry hair and rinse out after 10 minutes
• Avoid in patients allergic to chrysanthemums
• 20-30% of eggs remain viable after treatment
• Requires second treatment in 7-10 days to kill newly emerged nymphs 2

Second-Line Treatment Options (for Resistant Cases)

Malathion 0.5% Lotion

• Apply to hair and allow to air dry
• Leave on for 8-12 hours before washing off
• Advantages: High ovicidal activity, often requiring only a single application 2, 4
• Cautions: Highly flammable due to high alcohol content; risk of respiratory depression if ingested 2
• Should be used only in cases resistant to first-line treatments 2

Ivermectin

• Oral dosing: 200 μg/kg repeated in 10 days, or 400 μg/kg repeated in 7 days 2
• Topical 1% preparation: Apply for 10 minutes 1
• Limitations: Not FDA-approved for head lice; risk of neurotoxicity in young children
• Should not be used in children weighing less than 15 kg 2, 1

Lindane 1% (Not Recommended)

• The American Academy of Pediatrics no longer recommends lindane due to:
  • Low ovicidal activity
  • Risk of seizures
  • Widespread resistance 2
• Should only be used when other treatments cannot be tolerated or have failed 2
• Contraindicated in neonates, pregnant/breastfeeding women, and children <10 years 2

Treatment Algorithm

1. Confirm diagnosis by visualizing live lice (not just nits)
2. First attempt: Permethrin 1% cream rinse
3. If treatment fails after 7-10 days:
   • Verify proper application technique
   • Consider resistance and switch to malathion 0.5%
4. For persistent cases:
   • Consider ivermectin (oral or topical) for patients >15kg
   • Consider combination therapy with permethrin and trimethoprim/sulfamethoxazole for multiple treatment failures 5

Additional Management Considerations

Nit Removal

• Not necessary to prevent spreading but recommended for aesthetic reasons
• Use fine-toothed combs to remove nits
• Vinegar or vinegar-based products applied for 3 minutes before combing help loosen nits 2, 1

Environmental Measures

• Machine wash hats, scarves, bedding in hot water
• Dry using hottest setting for at least 20 minutes
• Soak combs and brushes in hot water for at least 10 minutes
• Vacuum carpets, furniture, and car seats used by affected individuals 1

Household Management

• Check all household members and treat those with live lice or eggs within 1 cm of scalp
• Treat family members who share a bed with the infected person 2

Topical Reactions

• Itching or mild burning may persist for days after treatment
• Not a reason for retreatment
• Consider topical corticosteroids and oral antihistamines for relief 2, 1

School Considerations

• "No-nit" policies are not recommended as nits can persist after successful treatment 6, 7
• Children should be allowed to return to school after proper treatment 2

Common Pitfalls

1. Misdiagnosis: Confirm active infestation by finding live lice, not just nits
2. Noncompliance with treatment protocol: Ensure proper application and timing
3. Reinfestation: Check and treat all close contacts
4. Premature retreatment: Itching alone doesn't indicate treatment failure
5. Overuse of pediculicides: Unnecessary treatments increase resistance risk
6. Inadequate environmental cleaning: Focus on items in direct contact with head

By following this treatment algorithm and considering these management principles, most cases of head lice can be successfully treated with minimal complications.