How long should a lice treatment be left on the head? - briefly
Leave the product on the scalp for the duration specified on the label—typically 10 minutes for OTC shampoos and 8–12 hours for prescription lotions. Follow the instructions precisely to ensure effectiveness and avoid resistance.
How long should a lice treatment be left on the head? - in detail
The contact time for a lice‑removing product determines its effectiveness. Most over‑the‑counter shampoos, lotions, or sprays containing permethrin or pyrethrin specify a minimum of 10 minutes on the scalp before rinsing. For prescription options such as malathion, the label typically requires 8–12 minutes. Dimethicone‑based treatments, which work by coating the insects, often advise a longer exposure of 30 minutes to an hour because the substance must fully envelop the lice and nits.
Key points for proper application:
- Follow the exact minutes printed on the package; shortening the period reduces kill rates.
- Apply to dry hair unless the instructions state otherwise; wet hair can dilute the active ingredient.
- Ensure thorough coverage from the scalp to the tips of all strands, especially behind the ears and at the nape.
- After the prescribed time, rinse with lukewarm water and remove dead insects with a fine‑toothed comb.
- A second treatment is usually required 7–10 days later to eliminate newly hatched nits that survived the first exposure.
Special considerations:
- Children under two years often receive a reduced exposure time (5–7 minutes) or a different, milder formulation.
- Sensitive scalps may react to longer contact; in such cases, a shorter duration approved by a healthcare professional is acceptable.
- Resistance to pyrethroids has been documented; when failure occurs after two applications, switch to a non‑neurotoxic option such as dimethicone or a prescription oral medication.
Monitoring after treatment involves checking the hair daily for live lice and using a nit comb for at least two weeks. Persistence of live insects after the second application indicates the need for medical evaluation and possibly an alternative regimen.