How long do lice eggs live? - briefly
Under normal temperature and humidity, lice eggs hatch in 7–10 days. If they fail to hatch, they can stay viable for up to about two weeks.
How long do lice eggs live? - in detail
Lice eggs, commonly called nits, remain viable for a limited period before hatching. The incubation interval depends on species, temperature, and humidity.
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Head lice (Pediculus humanus capitis): under typical indoor temperatures (20‑25 °C or 68‑77 °F) eggs hatch after 7‑10 days. Cooler environments extend the period to up to 14 days; warmer conditions may shorten it to 5‑6 days. After hatching, the empty shell is no longer alive.
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Body lice (Pediculus humanus corporis): eggs develop similarly, requiring 7‑10 days at normal room temperature. The same temperature range influences the timeline as with head lice.
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Pubic lice (Pthirus pubis): embryogenesis lasts 8‑12 days, again affected by ambient heat and moisture.
Viability ends when the embryo reaches the nymph stage and emerges. If an egg is not fertilized or the environment is unsuitable (e.g., extreme cold, desiccation), the egg will die before the expected hatch window. In practice, eggs older than 14 days are unlikely to produce viable lice, especially if they have been exposed to treatment agents that penetrate the shell.
Understanding these timelines informs control measures: effective treatment must target both live insects and the remaining eggs within the known incubation window to prevent re‑infestation.