Head lice: how long do they live in a bed? - briefly
Adult lice survive off a human scalp for only about one to two days; nymphs may live slightly longer but usually die within 48 hours without a host.
Head lice: how long do they live in a bed? - in detail
Head lice (Pediculus humanus capitis) require a human scalp for feeding. When separated from a host, they can persist on fabrics such as mattresses, sheets, or pillowcases, but survival is limited by moisture and temperature.
The adult female can live up to 48 hours without a blood meal; males survive a similar period. Nymphs, which have not yet fed, die within 24 hours. These limits apply to dry, ambient conditions typical of a bedroom.
Factors influencing off‑host longevity:
- Humidity: 40‑60 % relative humidity extends survival to the maximum 48 hours. Below 30 % humidity, death occurs within 12‑18 hours.
- Temperature: 20‑25 °C (68‑77 °F) is optimal. Temperatures above 30 °C accelerate dehydration, reducing survival to under 12 hours; below 10 °C slows metabolism but still leads to death within 48 hours.
- Fabric type: Natural fibers (cotton, linen) retain more moisture than synthetic blends, modestly increasing lifespan. Rough textures do not provide shelter; lice cling to smooth surfaces only briefly.
- Cleaning actions: Vacuuming, laundering at ≥60 °C (140 °F), or steam treatment eliminates all stages instantly.
Practical implications:
- Immediate response: Remove and launder bedding within 24 hours of detection.
- Extended precaution: Isolate unwashed items for at least 48 hours in a dry environment; lice will not survive beyond this window.
- Environmental control: Maintain bedroom humidity below 30 % and temperature near 20 °C to shorten off‑host survival.
In summary, head lice cannot remain viable on a bed for more than two days, with most dying within one day under typical household conditions. Prompt laundering and environmental management effectively break the transmission cycle.