How long do lice live indoors? - briefly
Lice survive on surfaces such as bedding or furniture for no more than 48 hours before dying without a host. On a human scalp they complete their life cycle in roughly 30 days.
How long do lice live indoors? - in detail
Lice that inhabit indoor environments complete their life cycle on a human host. The developmental stages—egg, nymph, and adult—each have specific time frames that together determine overall longevity.
The egg, commonly called a nit, requires 7‑10 days to hatch under typical indoor temperatures (20‑30 °C) and relative humidity of 70‑80 %. After emergence, the nymph passes through three molts. Each molt lasts approximately 3‑4 days, resulting in a total nymphal period of about 9‑12 days. Once maturity is reached, the adult louse lives for roughly 30 days, provided continuous access to a blood meal. Reproduction begins within 24‑48 hours of adulthood, with a female laying 6‑10 eggs per day.
Survival off the host is limited. In the absence of a blood source, an adult louse can endure 24‑48 hours, extending to a maximum of 72 hours under optimal indoor conditions (stable temperature, high humidity). Eggs remain viable for up to 10 days without a host, after which embryonic development ceases.
Key factors influencing indoor lifespan:
- Temperature: 25‑30 °C accelerates development; temperatures below 20 °C slow it markedly.
- Humidity: 70‑80 % supports egg viability and adult activity; lower humidity reduces survival time.
- Host availability: Continuous contact with a human host is essential for adult sustenance and reproduction.
- Environmental cleanliness: Regular laundering of bedding and clothing removes nits, interrupting the cycle.
Overall, a complete indoor infestation can persist for 4‑6 weeks from the appearance of the first egg to the death of the final adult, assuming favorable environmental conditions and uninterrupted host access. Prompt removal of nits and reduction of favorable indoor parameters are necessary to curtail the lifespan of the parasite.