How long do lice live away from a human? - briefly
Adult lice can survive without a host for roughly one to two days before they die from dehydration. Nymphs die even sooner, usually within 24 hours.
How long do lice live away from a human? - in detail
Lice require a human host for nutrition and moisture. When separated from a person, they can survive only a limited period, depending on species, temperature, humidity, and access to food sources.
Survival limits
- Under optimal indoor conditions (20‑25 °C, 50‑70 % relative humidity), adult head lice may live 24–48 hours without a host.
- In cooler, drier environments, survival drops to 6–12 hours.
- Nymphs and eggs are more vulnerable; they typically perish within 12 hours when removed from a scalp.
- Body lice, which can feed on clothing, survive longer, up to 5–7 days if clothing remains moist and warm.
Factors influencing longevity
- Temperature – Temperatures above 30 °C accelerate dehydration; below 10 °C slows metabolism but also reduces viability.
- Humidity – High humidity slows desiccation, extending life; low humidity causes rapid water loss.
- Food availability – Without access to blood, metabolic reserves are exhausted quickly.
- Life stage – Adults possess larger energy stores than nymphs, granting a slightly longer off‑host window.
Practical implications
- Items that may harbor lice (combs, hats, pillowcases) should be washed in hot water (≥ 60 °C) or sealed in plastic for at least 48 hours to ensure death.
- Vacuuming carpets and upholstery reduces the chance of temporary survival on surfaces.
- For body lice, laundering clothing at high temperature or storing it in a sealed bag for a week eliminates the insects.
Overall, head lice cannot persist beyond two days away from a person under typical indoor conditions, while body lice may endure up to a week when clothing remains favorable.