How long does treatment for lice last? - briefly
A typical lice regimen spans about one week, followed by a second dose around day 7 to eradicate any newly hatched nits.
How long does treatment for lice last? - in detail
Effective lice eradication typically involves two stages: an initial application of a pediculicide and a follow‑up treatment 7–10 days later. The first step eliminates active nymphs and adult insects; eggs (nits) often survive because most products cannot penetrate the cement that holds them to hair shafts. Consequently, a second dose is required to kill newly hatched nymphs before they reach reproductive maturity.
The interval between applications is critical. Most over‑the‑counter shampoos, lotions, or sprays contain permethrin, pyrethrin, or dimethicone and specify a repeat treatment after 7 days. Prescription options such as malathion or ivermectin may recommend a 9‑day interval. Extending the gap beyond 10 days reduces efficacy, as surviving nymphs can mature and lay new eggs.
In practice, the total treatment period ranges from 7 to 14 days, encompassing:
- Day 0: First application according to product instructions (usually left on scalp for 10 minutes, then rinsed).
- Day 7–9: Second application to target hatchlings.
- Day 10–14: Inspection and removal of residual nits with a fine‑toothed comb; repeat combing every 2–3 days if any are found.
If live lice are detected after the second round, an additional treatment may be necessary, extending the process by another 7 days. Environmental control (washing bedding, clothing, and personal items at ≥130 °F or sealing them in plastic bags for two weeks) should occur concurrently to prevent re‑infestation.
Overall, a complete eradication cycle is achieved within two weeks when the protocol is followed precisely and thorough nit removal is performed.