How quickly do lice reproduce on people’s heads? - briefly
A female head louse lays 5–10 eggs each day; the eggs hatch in 7–10 days and the nymphs become sexually mature after an additional 9–12 days, so a new generation can emerge roughly every two weeks.
How quickly do lice reproduce on people’s heads? - in detail
Pediculus humanus capitis, the head louse, completes its life cycle in approximately 7–10 days under optimal conditions (temperature ≈ 30 °C, humidity ≈ 70 %). An adult female lays about 6–10 eggs (nits) per day, depositing them firmly to the hair shaft near the scalp. Egg incubation lasts 7–10 days; after hatching, the nymph undergoes three molts over 4–6 days before reaching adulthood. Consequently, a single fertile female can generate up to 50–100 viable offspring within three weeks.
Key factors influencing the reproductive pace:
- Environmental temperature: Higher temperatures accelerate embryonic development and nymphal growth; at 20 °C the cycle extends to 12–14 days.
- Humidity: Adequate moisture prevents egg desiccation; low humidity reduces hatchability.
- Host grooming: Frequent combing or shampooing removes nits, lowering effective reproductive output.
- Population density: Overcrowding can increase mortality due to competition for blood meals.
Because each adult requires a blood meal every 3–4 hours, the feeding frequency sustains rapid growth and egg production. In a typical infestation, the population can double roughly every 5–7 days, reaching detectable levels within two weeks if untreated. Early intervention—removing nits and applying approved pediculicides—interrupts this exponential increase and prevents the infestation from reaching the peak reproductive capacity.