After how many days should a lice treatment be repeated? - briefly
Repeat the treatment 7 days after the first application, or follow the product’s label which often recommends a second dose 7–10 days later. This timing targets newly hatched lice that survived the initial treatment.
After how many days should a lice treatment be repeated? - in detail
The interval for a second application of a pediculicide depends on the life cycle of the head‑lice and the specific active ingredient. Eggs hatch in roughly 7–10 days; therefore the follow‑up dose must occur after the earliest possible emergence to eliminate newly emerged nymphs before they reproduce.
Common recommendations
- Permethrin 1 % (OTC): apply a second dose 7 days after the first treatment.
- Pyrethrin‑based products: repeat at day 7.
- Malathion 0.5 % (prescription): reapply at day 9–10.
- Benzyl alcohol lotion (5 %): a single application is sufficient; a second dose is not required because the product kills only live insects, not eggs.
- Spinosad 0.9 % (prescription): repeat at day 7 if live lice are still observed.
- Ivermectin lotion (prescription): a single dose is usually enough; a repeat may be advised at day 7 for persistent infestations.
When additional applications are warranted
- Documented resistance to the initial agent.
- Persistent live lice observed after the first treatment and a 7‑day interval.
- Heavy infestations confirmed by multiple nits on a single hair strand.
Practical steps for each treatment cycle
- Apply the product according to manufacturer instructions, ensuring full coverage of dry hair.
- Comb the hair with a fine‑toothed nit comb 24 hours after application to remove loosened nits.
- Wash bedding, hats, and personal items in hot water (≥ 130 °F) or seal them in plastic bags for two weeks.
- Perform the repeat application on the day specified for the chosen product, then repeat the nit‑combing process 24 hours later.
Adhering to the product‑specific re‑treatment schedule—generally a 7‑ to 10‑day gap—covers the hatch window and prevents the population from re‑establishing. Continuous monitoring for live lice over the subsequent week confirms the success of the regimen.