How quickly do lice reproduce on humans? - briefly
Female head lice reach reproductive maturity roughly 9–12 days after hatching and lay 5–10 eggs every 1–2 days, completing a life cycle in about 20–25 days. This rapid turnover permits multiple generations to develop within a single month on an infested person.
How quickly do lice reproduce on humans? - in detail
Human head lice (Pediculus humanus capitis) complete a life cycle in 7‑10 days under typical indoor temperatures (20‑30 °C) and relative humidity of 70‑80 %. An adult female lays 5‑7 eggs per day, up to 100 eggs over her lifespan of about 30 days. Eggs (nits) hatch after 7‑10 days. Nymphs emerge, pass through three molts, each lasting roughly 2‑3 days, before reaching reproductive maturity. Consequently, a single female can generate a new generation in just over a week, and population size may double every 5‑6 days when conditions are optimal.
Key factors influencing the reproduction rate:
- Temperature: higher ambient temperatures shorten egg incubation and nymphal development.
- Humidity: low humidity reduces egg viability; optimal moisture accelerates growth.
- Host grooming: frequent hair washing or combing removes nits, extending the interval between generations.
- Nutritional status of the host: adequate blood supply supports faster nymph development.
Typical progression on an untreated host:
- Day 0‑1: Adult female attaches to scalp, begins laying eggs.
- Day 7‑10: First batch of eggs hatch; nymphs appear.
- Day 12‑15: First molt; nymphs become second‑stage.
- Day 15‑18: Second molt; nymphs become third‑stage.
- Day 18‑21: Final molt; nymphs become reproductive adults.
- Day 22‑30: New females start laying eggs, initiating the next cycle.
Under optimal indoor conditions, a small infestation can expand from a few individuals to dozens within three weeks. Interrupting any stage—removing nits, reducing temperature, or lowering humidity—significantly slows population growth.