How long do lice survive without a host? - briefly
Head lice survive about 24–48 hours without a human host before dying from dehydration. Body lice can endure up to five days without a blood source, but also perish when deprived of a host.
How long do lice survive without a host? - in detail
Lice can remain alive for a limited period when detached from a human or animal host. Survival time depends on species, life stage, temperature, and humidity.
Adult head‑lice (Pediculus humanus capitis) lose vitality within 24–48 hours at ambient room temperature (20–25 °C) and moderate humidity (40–60 %). In cooler, dry environments they may die in as little as 12 hours, while a warm, humid setting (30 °C, >70 % relative humidity) can extend viability to roughly 72 hours.
Body‑lice (Pediculus humanus corporis) exhibit similar limits. Adults survive 1–2 days under typical indoor conditions; high humidity prolongs survival, low humidity shortens it.
Crab lice (Pthirus pubis) are less tolerant of desiccation; they generally perish within 24 hours when removed from a host.
Nymphs and freshly hatched nits are more resilient to dehydration. Nymphs may endure up to 48 hours without feeding, while eggs (nits) can remain viable for several weeks if environmental conditions are favorable, but they will not hatch without a host to provide warmth and carbon dioxide.
Key factors influencing off‑host longevity:
- Temperature: Below 15 °C accelerates mortality; above 30 °C slows it but may increase dehydration.
- Relative humidity: Above 70 % reduces water loss, extending survival; below 30 % causes rapid desiccation.
- Airflow: Strong air currents increase evaporation, shortening lifespan.
- Life stage: Eggs are the most durable; adults are the least.
In practice, infestations cannot be sustained beyond a few days without a living host, making prompt removal of infested clothing and bedding an effective control measure.