How long do lice live after treatment? - briefly
Lice generally die within one to two days after an effective treatment, while any remaining eggs usually hatch within a week if not removed. Continuous follow‑up checks are necessary to confirm eradication.
How long do lice live after treatment? - in detail
Lice that have been exposed to an effective pediculicide typically die within a few hours. Most chemical products act on the nervous system of the insect, causing paralysis and death in 30 minutes to 2 hours after contact. After the insect’s body is immobilized, residual activity of the active ingredient continues to affect any surviving stages for up to 24 hours.
The life cycle of head lice provides additional context for the post‑treatment window. An adult female lays 6–10 eggs (nits) each day; each egg hatches in about 7–10 days. Nymphs mature to reproductive adults in another 7–10 days. Because most treatments do not penetrate the protective shell of a nit, eggs remain viable until they hatch. Consequently, a single application eliminates only the live insects present at the time of treatment; newly emerged nymphs can appear up to 10 days later.
Practical implications:
- Immediate kill phase: 30 minutes – 2 hours after application.
- Residual effect: up to 24 hours, preventing re‑attachment of surviving lice.
- Re‑emergence risk: 7–10 days post‑treatment, when unhatched eggs hatch.
- Recommended follow‑up: a second treatment 7–10 days after the first, targeting any newly emerged nymphs.
- Mechanical removal: combing with a fine‑toothed lice comb can physically extract live lice and nits; repeated sessions over 2‑3 weeks are needed to ensure complete eradication.
In summary, the insects die quickly after exposure, but the protective egg stage can sustain the infestation for up to ten days, necessitating a scheduled retreat and diligent combing to achieve total clearance.