How quickly do lice reproduce on a person's head? - briefly
Female head lice deposit 5–6 eggs daily, which hatch in 7–10 days, and the resulting nymphs mature into reproductive adults about 9–12 days later; thus a full reproductive cycle completes in roughly two weeks.
How quickly do lice reproduce on a person's head? - in detail
Head lice (Pediculus humanus capitis) complete their life cycle on a human scalp in a tightly defined timeframe. An adult female deposits 5–10 eggs (nits) each day, attaching them to hair shafts near the scalp. The incubation period for each egg lasts 7–10 days, after which a nymph emerges.
The nymph undergoes three successive molts before reaching adulthood. Each molt occurs roughly every 3 days, so full maturation from hatch to fertile adult takes about 9–12 days. Once sexually mature, a female can lay up to 10 eggs per day for a period of 20–30 days, depending on environmental conditions and host factors.
Because of these intervals, a single fertile female can produce 50–100 offspring within a month. Under optimal temperature (30–32 °C) and humidity (70–80 %), the population can double every 5–7 days. In cooler or drier conditions, development slows, extending the egg stage to 12 days and lengthening the nymphal period to 14 days.
Key stages and timing:
- Egg deposition: 5–10 eggs/day per female
- Egg incubation: 7–10 days
- Nymphal development (3 molts): ~9–12 days total
- Sexual maturity: reached at ~10 days post‑hatch
- Adult reproductive span: 20–30 days, 5–10 eggs/day
Factors influencing reproductive speed include scalp temperature, humidity, hair length, and frequency of head washing or combing. Regular removal of nits and thorough treatment interrupt the cycle, preventing the exponential increase that can occur within a few weeks.