How long before re‑treating lice? - briefly
A second application is typically advised 7–10 days after the initial treatment to target newly hatched nymphs. If live lice remain after that interval, repeat the treatment following the product’s instructions.
How long before re‑treating lice? - in detail
The recommended interval between the initial lice elimination product and a subsequent application is typically 7 to 10 days. This window allows any newly hatched nymphs, which were protected from the first dose, to emerge and become vulnerable to the second treatment.
The timing is based on the life cycle of head‑lice:
- Eggs (nits) hatch in about 7‑9 days after being laid.
- Newly emerged lice reach maturity within 24‑48 hours.
- The first treatment usually kills live insects but does not affect viable eggs.
Applying a second dose after the hatch period ensures that the newly emerged lice are eradicated before they can reproduce. Most over‑the‑counter products specify a repeat treatment 9 days after the first application; some professional options advise a 10‑day interval.
Additional considerations:
- Follow the exact instructions on the label; some formulations require a shorter or longer gap.
- If a prescription medication is used, the prescribing physician may set a different schedule.
- In cases of severe infestation, a third application may be recommended, spaced another 7‑10 days after the second dose.
- After each treatment, remove nits with a fine‑toothed comb to reduce the chance of re‑infestation.
Adhering to the 7‑10‑day repeat schedule aligns with the biological development of the pest and maximizes the probability of complete eradication.