What kills nits and lice? - briefly
Pediculicidal agents such as permethrin, pyrethrin, malathion, spinosad or ivermectin effectively eradicate both lice and their eggs when applied according to label instructions and combined with fine‑tooth nit combing. Complementary steps—washing clothing and bedding in water ≥130 °F, drying on high heat, and sealing non‑washable items for two weeks—help ensure complete elimination.
What kills nits and lice? - in detail
Effective elimination of head‑lice insects and their eggs relies on agents that either poison the organism or destroy the egg shell through physical means. Chemical insecticides work by disrupting the nervous system of the parasite; physical methods damage the protective structures of the egg or the louse’s body.
Insecticidal options
- Permethrin (1 %) – synthetic pyrethroid; kills active lice within minutes, but requires a second application 7‑10 days later to target newly hatched nits.
- Pyrethrin (0.5 %) with piperonyl‑butoxide – natural extract enhanced by a synergist; effective against susceptible strains, resistance may develop.
- Malathion (0.5 %) – organophosphate; kills both lice and nits by inhibiting acetylcholinesterase; contraindicated for children under six months and pregnant women.
- Spinosad (0.9 %) – bacterial‑derived compound; rapid lice mortality, minimal effect on nits, recommended single‑dose regimen.
- Ivermectin (0.5 %) – macrocyclic lactone; oral or topical formulations; eliminates lice, limited activity on nits, requires repeat dosing.
- Benzyl alcohol (5 %) – non‑neurotoxic; suffocates lice, does not affect eggs; necessitates two‑week treatment course.
- Dimethicone (silicone‑based) – coats lice, causing dehydration; effective on resistant populations, does not dissolve eggs.
Physical treatments
- Wet combing – fine‑toothed metal comb used on damp hair; removes live lice and most nits in repeated sessions over 2‑3 weeks.
- Heat application – devices delivering ≥ 50 °C to hair for several minutes; destroys eggs and kills lice instantly; requires thorough coverage.
- Steam or hot water – washing hair in water > 46 °C for at least 10 minutes; lethal to both stages, but may be uncomfortable.
- Freezing – sealed items (bedding, hats) placed at –20 °C for ≥ 48 hours; kills insects and eggs on non‑wearable objects.
Natural substances (limited evidence)
- Tea tree oil (5‑10 % dilution) – topical antiseptic; some studies show reduced lice counts, but egg mortality is inconsistent.
- Neem oil (2‑5 %) – insect‑repellent properties; may assist in reducing infestation when combined with mechanical removal.
- Vinegar or lemon juice – acidic solutions; can loosen nits from hair shaft, facilitating combing, but do not kill lice directly.
Safety and protocol considerations
- Verify age‑appropriate usage; many synthetic insecticides are prohibited for infants and pregnant users.
- Perform a patch test for topical agents to detect allergic reactions.
- Follow label instructions for application duration, drying time, and required repeat doses.
- Combine chemical or physical treatment with thorough cleaning of personal items: wash clothing and bedding at ≥ 60 °C, seal non‑washable objects in airtight bags for 2 weeks.
- Re‑examine hair after each treatment session; remove any residual nits with a fine comb to prevent re‑infestation.
A comprehensive approach—selecting an effective agent, applying it correctly, and supplementing with diligent mechanical removal—provides the highest probability of eradicating both adult parasites and their eggs.