How long do lice and fleas live? - briefly
Adult head lice live roughly 30 days on a human, with eggs hatching in 7‑10 days; body lice have a similar lifespan of about 30 days. Adult fleas survive 2‑3 weeks on a host but can remain dormant for several months in cool conditions.
How long do lice and fleas live? - in detail
Lice and fleas are obligate ectoparasites whose survival depends on a blood‑feeding host. Their life cycles consist of egg, immature (nymph) stages, and mature adult, each with characteristic durations that determine the total period an individual can remain alive on or off a host.
- Head‑lice (Pediculus humanus capitis) – eggs hatch in 7–10 days; three nymphal molts require another 5–7 days; adults live 30 days on a human head, longer if they find a new host.
- Body‑lice (Pediculus humanus corporis) – similar egg and nymph periods; adult lifespan extends to 40 days, reflecting the ability to survive in clothing and move between hosts.
- Pubic‑lice (Pthirus pubis) – eggs hatch in 6–10 days; three nymphal stages last about 9 days; adults survive up to 30 days on a human body region.
Fleas exhibit comparable stage lengths but differ in adult longevity:
- Cat flea (Ctenocephalides felis) – eggs hatch in 2–5 days; four larval instars develop over 5–20 days; pupae emerge as adults after 5–10 days; adults live 2–3 months when feeding regularly, up to 6 months without a host in cool conditions.
- Dog flea (Ctenocephalides canis) – egg‑to‑adult timeline mirrors the cat flea; adult lifespan ranges from 1 month (host‑deprived) to 3 months (continuous blood meals).
- Human flea (Pulex irritans) – eggs hatch in 2–5 days; larval development 7–14 days; adult lifespan 2–3 months with host access, shorter under adverse temperatures.
Environmental temperature, humidity, and host availability markedly influence each stage. Warmer climates accelerate egg hatching and larval development, while low humidity hampers egg viability. Absence of a suitable host forces adults into a dormant state, reducing metabolic activity and extending survival time but ultimately leading to mortality within weeks to months.
Understanding these temporal parameters informs control strategies: treatment regimens must target eggs, nymphs, and adults within the window defined by the longest developmental stage, typically 10 days for lice and up to 20 days for flea pupae. Re‑infestation risk persists until the entire population, including dormant stages, is eliminated.