Head Lice and Swimming: Chlorine Efficacy and Effective Treatment

Swimming in chlorinated pools does not reliably kill head lice (Pediculus humanus capitis) or nits. Lice can survive submersion for hours by entering a state of suspended animation (closing spiracles). Chlorine concentrations in pools (1-3 ppm) are insufficient for pediculicidal activity.

Evidence-Based Treatment

1. First-line topical pediculicides:
   • Permethrin 1% (OTC) — resistance common
   • Pyrethrins + piperonyl butoxide (OTC)
   • Malathion 0.5% (Rx) — ovicidal; flammable
   • Spinosad 0.9% (Rx) — ovicidal; single application often sufficient
   • Ivermectin 0.5% lotion (Rx) — single application
2. Wet combing (mechanical removal): Conditioner + fine-tooth nit comb every 3-4 days for 2 weeks; effective adjunct or standalone for resistant cases/pregnant women
3. Oral ivermectin (200 mcg/kg, repeated day 7-10): For refractory cases; off-label in US

Environmental Measures

• Wash bedding/clothing in hot water (≥55°C/130°F) + high-heat dry
• Vacuum upholstery/carpets (lice survive <48h off host)
• Seal non-washables in plastic bags ×2 weeks
• Do not use environmental sprays/foggers (unnecessary, toxic)

Key Points

• Lice do not jump/fly; spread by direct head-to-head contact
• Nits >1cm from scalp = likely nonviable (hatched or dead)
• Treat only confirmed active infestations (live lice)
• School "no-nit" policies not recommended by AAP/NASN
• Resistance to permethrin/pyrethrins widespread; consider newer agents first-line

Consult pediatrician or pharmacist for age-appropriate product selection.