How many days does a louse nit live? - briefly
A louse egg typically remains viable for 7–10 days before hatching, with warmer conditions accelerating development. After this period the nit either emerges as a nymph or ceases to be viable.
How many days does a louse nit live? - in detail
A louse nit is the egg stage of a human‑infesting louse. Its existence ends when the embryo emerges as a nymph; therefore the “lifespan” refers solely to the incubation period.
The duration of embryonic development varies with species and environmental conditions:
- Head louse (Pediculus humanus capitis): 6–9 days at typical indoor temperatures (≈30 °C). Cooler settings (≈20 °C) can extend development to 10–12 days.
- Body louse (Pediculus humanus humanus): 7–10 days under similar temperature ranges; humidity above 70 % shortens the period, while dry air lengthens it.
- Pubic louse (Pthirus pubis): 8–12 days; the larger egg size and slower metabolism contribute to a slightly longer timeline.
Key factors influencing the incubation interval:
- Temperature: Higher ambient heat accelerates embryogenesis; each 1 °C rise reduces the period by roughly 0.5 day.
- Relative humidity: Levels above 60 % favor faster development; low humidity can delay hatching by 1–2 days.
- Egg viability: Fertilized eggs hatch; unfertilized or damaged eggs remain dormant and eventually desiccate.
- Chemical exposure: Ovicidal treatments (e.g., dimethicone, permethrin) can kill embryos before hatching, effectively terminating the egg’s existence.
Once the nymph emerges, the empty shell, often called a “shell,” persists on the hair shaft but no longer constitutes a living stage. Consequently, the measurable period for a nit is confined to the embryonic phase, typically ranging from six to twelve days depending on species and conditions.