How does a lice and nit treatment work? - briefly
The treatment delivers a chemical that disables or kills adult lice and a surfactant that dissolves the adhesive bonding nits to the hair, facilitating their removal. A second application 7‑10 days later eradicates any newly hatched insects before they can mature.
How does a lice and nit treatment work? - in detail
Lice and nit eradication relies on chemical or physical agents that disrupt the insect’s nervous system, cuticle integrity, or reproductive capacity. The primary components of most over‑the‑counter preparations are neurotoxic insecticides such as permethrin, pyrethrins, or dimethicone. Permethrin and pyrethrins bind to voltage‑gated sodium channels in the louse’s nerve cells, causing prolonged depolarization, paralysis, and death. Dimethicone, a silicone‑based oil, coats the exoskeleton, blocks spiracles, and suffocates the parasite without affecting the host’s skin.
A typical treatment regimen proceeds in three phases:
- Application – The product is applied to dry hair, saturated from scalp to tips, and left for the manufacturer‑specified duration (usually 5–10 minutes). This period allows the active ingredient to penetrate the cuticle and reach the nervous system or respiratory openings.
- Rinsing – Hair is thoroughly washed with water, sometimes followed by a mild shampoo to remove residual chemicals. Rinsing eliminates dead insects and excess formulation, reducing irritation risk.
- Re‑treatment – A second application is performed 7–10 days after the first, targeting newly hatched nits that survived the initial exposure because they were not yet viable. This interval aligns with the lice life cycle, ensuring complete eradication.
Adjunctive measures enhance efficacy:
- Nit combing – Fine‑toothed metal or plastic combs mechanically remove eggs and dead lice. Repeated combing every 2–3 days for two weeks maximizes removal of residual nits.
- Environmental control – Items that contact the head (pillows, hats, brushes) are washed in hot water (≥ 60 °C) or sealed in plastic bags for 48 hours to prevent re‑infestation.
- Resistance monitoring – In regions where permethrin resistance is documented, alternative agents such as malathion, spinosad, or benzyl alcohol may be prescribed. Resistance occurs through mutations in sodium channel genes, reducing insecticide binding affinity.
The pharmacodynamics of dimethicone differ from neurotoxic insecticides. By forming a continuous film, it physically obstructs gas exchange, leading to dehydration and death within hours. Because it lacks systemic toxicity, dimethicone is suitable for children under two years and individuals with sensitivities to conventional insecticides.
Effectiveness hinges on proper dosage, adherence to timing, and thorough removal of eggs. Failure to follow the re‑treatment interval or to comb out nits often results in treatment failure, as viable eggs hatch and repopulate the scalp.