How long does a louse survive off a human on clothing? - briefly
A louse may remain viable on clothing for roughly one to two days before dehydration causes death. Survival beyond this period is unlikely under typical indoor conditions.
How long does a louse survive off a human on clothing? - in detail
Lice can remain alive on fabric only for a limited period, and survival depends on species, environmental conditions, and the type of clothing.
Head‑lice (Pediculus humanus capitis) are adapted to the scalp. Once removed from a host, they lose access to warmth and moisture. Under typical indoor temperatures (20‑22 °C) and relative humidity of 40‑60 %, adult head‑lice survive 24‑48 hours before succumbing. Nymphs die slightly faster, usually within 12‑24 hours. Extreme heat (>30 °C) accelerates mortality, reducing viability to a few hours, while refrigeration (4 °C) can extend survival up to 72 hours but does not support reproduction.
Body‑lice (Pediculus humanus humanus) are more tolerant of clothing because their life cycle includes laying eggs (nits) on seams. In moderate indoor conditions, adult body‑lice can live 48‑72 hours away from a host. Eggs remain viable for up to 7 days on fabric if the environment remains humid (≥70 %). However, hatching requires a human blood meal; without it, larvae die within 24 hours.
Key factors influencing off‑host longevity:
- Temperature: higher temperatures increase metabolic rate and dehydration, shortening life span; lower temperatures slow metabolism but do not halt death.
- Humidity: low humidity leads to rapid desiccation; high humidity prolongs survival.
- Fabric type: porous, breathable materials (cotton, wool) retain moisture longer than synthetic fibers, offering a marginally extended window.
- Life stage: adults outlive nymphs and eggs; eggs are the most resilient but require a host to develop.
Practical implications:
- Launder clothes at ≥60 °C or use a dryer on high heat for at least 30 minutes to ensure all stages are killed.
- Seal infested garments in a plastic bag for 48 hours; lack of blood meals will cause all lice to die.
- For short‑term isolation, placing clothing in a freezer at –20 °C for 24 hours is sufficient to eliminate viability.
In summary, detached lice on garments survive from several hours up to a few days, with adult body‑lice lasting the longest under optimal humidity and moderate temperature, while head‑lice are less tolerant and perish within two days at typical indoor conditions.