After how many days do lice die? - briefly
Head lice usually die within one to two days when they have no human host, though under ideal temperature and humidity they may survive up to a week. Adult lice cannot live longer than ten days without feeding.
After how many days do lice die? - in detail
Lice survive only a short period without a blood meal. An adult head louse can live 1–2 days on a dry surface; at room temperature 20‑25 °C it typically dies within 24 hours. Higher temperatures accelerate mortality, with 30 °C reducing survival to 12 hours. Lower humidity also shortens lifespan, whereas a moist environment may extend it to 48 hours, but never beyond 72 hours.
Nymphs—immature lice that have not yet reached adulthood—are even less resilient. After their first molt they can endure 12‑24 hours without a host. Their survival window matches that of adults, generally not exceeding 48 hours.
Eggs (nits) are the most durable stage. When detached from the scalp, a louse egg remains viable for 7‑10 days before it either hatches or becomes non‑viable. The embryo requires the warmth and humidity of the scalp to develop; without these conditions, the egg will not hatch and will eventually die.
Summary of off‑host survival:
- Adult lice: 24 hours (typical), up to 48 hours in humid, cool conditions.
- Nymphs: 12‑24 hours, max 48 hours under favorable moisture.
- Eggs: 7‑10 days before hatching; if not incubated, they die within that period.
Factors influencing mortality:
- Temperature – higher heat shortens life; below 15 °C slows metabolism but still leads to death within 48 hours.
- Humidity – low humidity desiccates lice quickly; high humidity marginally prolongs survival.
- Availability of blood – absence of a host forces starvation, the primary cause of death.
Understanding these timelines informs control measures: prompt removal of infested clothing and bedding, washing at ≥ 60 °C, and thorough cleaning of surfaces reduce the chance of re‑infestation because lice cannot survive beyond the periods outlined above.