How long do lice die after treatment? - briefly
Lice usually perish within minutes to a few hours after a correctly applied pediculicide, though residual eggs may hatch later and require a second application. Effectiveness depends on the product’s active ingredient and adherence to label instructions.
How long do lice die after treatment? - in detail
Lice are eliminated within a predictable timeframe after the application of approved pediculicides.
The active ingredient begins to affect adult insects almost immediately; mortality peaks between 30 minutes and 2 hours. Most products contain neurotoxic compounds that disrupt the parasite’s nervous system, causing rapid paralysis and death.
Eggs (nits) are more resistant. Chemical agents typically require at least 8 hours of contact to penetrate the protective shell. Consequently, a second treatment is recommended 7–10 days after the first dose to eradicate any newly hatched lice that survived the initial exposure.
Key points for each common class of treatment:
- Pyrethroids (e.g., permethrin 1 %) – adult death within 1 hour; eggs may survive, necessitating repeat application.
- Spinosads – adult mortality within 30 minutes; ovicidal activity modest, repeat treatment after 7 days advised.
- Ivermectin (topical or oral) – adult death within 2 hours; eggs largely unaffected, follow‑up dose after 7 days recommended.
- Malathion (0.5 %) – adult death within 1 hour; high ovicidal effect, but resistance reported; a second treatment may still be prudent.
Environmental control does not influence the immediate death of parasites on the host, but washing bedding, clothing, and personal items in hot water (≥ 130 °F/54 °C) or sealing them in plastic bags for 2 weeks prevents re‑infestation from surviving eggs.
In summary, adult lice perish within a few hours of proper medication, while eggs require extended exposure and a follow‑up dose approximately one week later to ensure complete eradication.