How are lice treated in humans? - briefly
Pediculicide shampoos or lotions—typically permethrin, pyrethrin, or dimethicone—are applied to the scalp, left for the specified duration, then rinsed, followed by meticulous combing with a fine‑toothed nit comb to extract eggs. Oral ivermectin or benzyl alcohol lotion serve as secondary options when topical treatments fail or are unsuitable.
How are lice treated in humans? - in detail
Effective management of human lice infestations requires a combination of chemical, mechanical, and environmental strategies. The three principal species—head lice (Pediculus humanus capitis), body lice (Pediculus humanus corporis), and pubic lice (Pthirus pubis)—each respond to specific interventions, though overlap exists.
Topical pediculicides remain the first‑line option. Permethrin 1 % lotion, applied to dry hair for ten minutes before rinsing, eliminates most live insects and nits. Pyrethrin formulations, combined with piperonyl butoxide, act similarly but demand strict adherence to exposure time. Malathion 0.5 % requires a longer contact period (8–12 hours) and is reserved for resistant cases. Spinosad 0.9 % suspension, applied for ten minutes, offers an alternative with a distinct mechanism that reduces cross‑resistance. Ivermectin 0.5 % cream, applied to the scalp and left for ten minutes, provides a single‑dose solution effective against resistant strains. All agents should be reapplied after seven days to target newly hatched nits.
Mechanical removal complements chemical treatment. A fine‑toothed nit comb, used on wet, conditioned hair, removes up to 80 % of viable eggs per pass. Repeated combing at 2–3 day intervals, for at least three sessions, is essential to eradicate the residual population.
Oral therapy is indicated when topical options fail or are contraindicated. Single‑dose ivermectin 200 µg/kg, taken with food, achieves systemic eradication of both head and pubic lice. Azithromycin 1 g, administered as a single oral dose, offers an alternative for pubic lice, though resistance data are limited.
Environmental control reduces reinfestation risk. Machine‑wash clothing, bedding, and towels in hot water (≥ 60 °C) and tumble‑dry on high heat for 30 minutes. Items that cannot be laundered should be sealed in plastic bags for two weeks, the duration of the lice life cycle. Vacuuming carpets and upholstered furniture removes detached nits and debris.
Resistance monitoring guides therapeutic choice. Documented permethrin and pyrethrin resistance necessitates rotating to non‑pyrethroid agents such as spinosad or oral ivermectin. Follow‑up examination at day 10 and day 14 confirms treatment success; absence of live lice and viable nits indicates cure.
In summary, optimal lice eradication combines approved topical insecticides, diligent nit removal, possible oral medication, and thorough decontamination of personal items, with repeat assessments to ensure complete resolution.