How long do louse nits live? - briefly
Louse eggs stay viable for approximately 7–10 days before hatching, after which the empty shells can remain attached for several weeks if they are not removed.
How long do louse nits live? - in detail
Lice eggs, commonly called nits, remain attached to a host’s hair shaft until the embryo hatches. The viable period of an egg is roughly 7 to 10 days under optimal conditions of temperature (around 30 °C) and humidity (50‑70 %). After this window, the egg either hatches or loses its capacity to develop.
Key factors influencing egg survival:
- Temperature: Below 20 °C, development slows dramatically, extending the pre‑hatch phase up to 14 days. Above 35 °C, embryonic mortality increases sharply.
- Humidity: Dry environments (<30 % relative humidity) cause desiccation, reducing viability to 3–5 days. Excessive moisture (>80 %) can promote fungal growth, also shortening lifespan.
- Host grooming: Frequent combing or use of pediculicide shampoos physically removes or damages eggs, effectively limiting their survival regardless of environmental conditions.
If an egg is not disturbed and environmental parameters stay within the optimal range, it will typically hatch on day 8 ± 2. Once hatched, the emerging nymph requires a blood meal within 24 hours to survive; failure to feed results in death within 48 hours. Consequently, the total lifespan of the egg stage does not exceed ten days, after which the organism either progresses to the next developmental stage or becomes non‑viable.