How long do lice live without hair? - briefly
Adult head lice can survive for up to 48 hours without a human host, while nymphs typically endure only 24‑36 hours. After this period, they die from dehydration and lack of blood meals.
How long do lice live without hair? - in detail
Lice require a blood meal every few hours; without access to a host they die rapidly. Under typical indoor conditions an adult head louse survives no longer than 24 hours, and most individuals perish within 12 hours. Some laboratory observations report survival up to 48 hours when temperature and humidity are optimal, but the average is closer to one day.
The insect’s metabolism dictates this short window. After a blood meal, a louse can remain inactive for several hours, but after exhausting stored nutrients it must locate a new source. Nymphs, which have not yet reached maturity, possess even lower energy reserves and usually die within 6–12 hours without feeding.
Environmental factors modify the lifespan outside a scalp:
- Temperature ≈ 25‑30 °C (77‑86 °F) – prolongs survival; lower temperatures increase mortality.
- Relative humidity ≥ 50 % – prevents desiccation; dry air can kill lice within a few hours.
- Absence of direct sunlight – ultraviolet radiation accelerates death.
Body lice (Pediculus humanus corporis) and pubic lice (Pthirus pubis) show similar limits, though body lice can endure slightly longer, up to 48 hours, because they inhabit clothing that retains moisture. Pubic lice, adapted to coarser hair, survive roughly the same period as head lice when detached.
Eggs (nits) cannot develop without the warmth and humidity provided by a human host. Unhatched nits die within 5–7 days, but they never hatch without a blood source.
Consequently, removal of infested hair or clothing eliminates the insects within a day, provided no new host is introduced. Preventive measures should focus on eliminating contact with infested individuals rather than relying on prolonged survival of detached lice.