How long do lice live on a person? - briefly
Adult head lice remain alive on a human host for roughly 30 days, assuming they obtain regular blood meals; nymphs develop in 7–10 days before reaching the same overall lifespan.
How long do lice live on a person? - in detail
Lice that inhabit a human host progress through three developmental stages: egg (nit), nymph, and adult. After hatching, a nymph requires a blood meal within 24 hours to survive; it then molts three times over approximately 4–7 days before reaching maturity. Adult head lice feed several times daily and can persist for about 30 days under optimal conditions, provided they obtain regular blood meals and remain at temperatures between 28 °C and 32 °C. Without access to a host, an adult’s survival drops sharply, with death occurring after 1–2 days of starvation.
Key factors influencing longevity on a person:
- Temperature: Cooler environments (below 20 °C) shorten the life span; higher temperatures accelerate metabolism and may reduce survival time.
- Blood availability: Interruptions in feeding, such as prolonged hair washing with hot water, can lead to mortality within 48 hours.
- Host hygiene: Frequent combing and use of pediculicide treatments diminish the viable population, often eliminating adults within a week.
- Species variation: Body lice (Pediculus humanus corporis) survive longer off‑host, up to 10 days, but on a person they exhibit a similar adult lifespan to head lice when regular feeding occurs.
Overall, an adult louse on a human can remain viable for roughly one month, while nymphs transition to adulthood within a week. Absence of blood or unfavorable conditions results in rapid decline, limiting survival to a few days.