Treatment Options for Head Lice (Pediculosis Capitis)
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% (OTC)
- Application method: Apply to damp, shampooed (with non-conditioning shampoo), towel-dried hair
- Duration: Leave on for 10 minutes, then rinse off
- Mechanism: Creates residue that kills emerging nymphs
- Retreatment: Repeat in 7-10 days if live lice are still seen
- Advantages: Low mammalian toxicity, no allergic reactions in people with plant allergies 1
- Limitations: Resistance has been reported, though prevalence is unknown
Pyrethrins + Piperonyl Butoxide (OTC)
- Application method: Apply to dry hair, allow to air dry
- Duration: Rinse after 8-12 hours (some studies suggest 20 minutes may be effective)
- Retreatment: Required in 7-10 days as 20-30% of eggs remain viable
- Contraindications: Avoid in patients with chrysanthemum allergies
- Limitations: Resistance has been reported 1, 2
Second-Line Treatment Options
Malathion 0.5% (Prescription)
- When to use: For patients ≥24 months with documented resistance to permethrin/pyrethrins
- Application method: Apply to hair, allow to air dry
- Duration: Wash off after 8-12 hours
- Advantages: High ovicidal activity, often single application is sufficient
- Cautions:
- Highly flammable (78% isopropyl alcohol content)
- Avoid hair dryers, curling irons, smoking during treatment
- Risk of respiratory depression if ingested
- Not for children <24 months 1
Ivermectin (Prescription)
- Oral dosing: 200 mg/kg repeated in 10 days, or 400 mg/kg repeated in 7 days
- Topical: 1% preparation applied for 10 minutes
- Limitations:
- Not FDA-approved for head lice
- Should not be used in children weighing <15 kg
- Risk of neurotoxicity in young children 1
Lindane 1% (Prescription)
- Duration: No more than 4 minutes, repeat in 9-10 days
- Cautions:
- FDA warning: use only when other treatments fail
- Risk of seizures, especially in children
- Low ovicidal activity (30-50% eggs not killed)
- Widespread resistance
- Not recommended by American Academy of Pediatrics
- Banned in California 1
Treatment Protocol
- Confirm diagnosis: Never treat without clear evidence of active infestation
- Select appropriate treatment: Start with permethrin 1% unless contraindicated
- Apply correctly: Follow specific product instructions
- Retreat as needed: Most treatments require a second application in 7-10 days
- Consider nit removal: While not necessary to prevent spread, recommended for aesthetic reasons and to reduce diagnostic confusion
- Use fine-toothed comb
- Consider vinegar-based products to loosen nits (apply 3 minutes before combing) 1
Environmental Measures
- Machine wash hats, scarves, bedding in hot water (>130°F/54°C) and dry using hottest setting for at least 20 minutes
- Soak combs/brushes in hot water (>130°F/54°C) for at least 10 minutes
- Vacuum carpets, mattresses, furniture, and car seats used by affected individuals 2
- Examine and treat all household members with live lice or eggs within 1 cm of scalp 1
Treatment Failures
Consider these factors before diagnosing resistance:
- Misdiagnosis
- Noncompliance with treatment protocol
- Reinfestation
- Lack of ovicidal properties of the product
- True resistance to pediculicide 1
Special Considerations
- 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 1
- Alternative treatments: Sulfamethoxazole-trimethoprim has been used but is not FDA-approved for head lice and carries risk of severe allergic reactions (Stevens-Johnson syndrome) 1
- Spinosad 0.9%: A newer prescription option that is effective against permethrin-resistant lice and has ovicidal properties 3
Remember that head lice do not transmit disease and primarily cause discomfort through itching. Treatment should be initiated promptly to reduce discomfort and prevent spread to others.