Where and how long do lice live? - briefly
Lice reside exclusively on the bodies of their hosts—human scalp hair, body hair, or the feathers and skin of birds and mammals. Their lifespan on a human host is typically 30 days, while other species may survive for several weeks under similar conditions.
Where and how long do lice live? - in detail
Lice are obligate ectoparasites that complete their entire life cycle on a host or in the immediate environment of the host. The most common species infest humans: head lice (Pediculus humanus capitis) reside on the scalp and attach eggs to hair shafts; body lice (Pediculus humanus humanus) live in the seams of clothing and lay eggs on fabric; pubic lice (Pthirus pubis) inhabit the coarse hair of the genital region and occasionally other body hair.
The preferred habitat for each species is determined by temperature, humidity, and the availability of suitable hair or fabric. Optimal conditions are temperatures between 29 °C and 32 °C and relative humidity of 70 %–80 %. Under these conditions, development proceeds rapidly.
Life‑cycle duration:
- Egg (nit): incubation period of 7–10 days at optimal temperature.
- Nymph: three molts over 9–12 days; each instar requires a blood meal.
- Adult: reaches reproductive maturity after the final molt; females lay 5–8 eggs per day.
Adult lice survive on the host for approximately 30 days, during which they continuously feed on blood. Off‑host survival is limited: head lice can endure 24–48 hours without a human, while body lice may persist up to 5 days in clothing, given sufficient humidity. Pubic lice exhibit similar off‑host limits, surviving up to 48 hours.
Environmental reservoirs are restricted to items that maintain the required microclimate, such as hats, scarves, bedding, or clothing seams. Once removed from these sources, lice rapidly desiccate and die.
In summary, lice inhabit specific regions of the human body or personal garments, thrive under warm and moist conditions, and complete a life cycle of roughly 30 days on a host, with a brief capacity to survive away from the host.