How many days after infestation do lice appear? - briefly
Eggs (nits) generally hatch in 7–10 days, and the emerging nymphs become visible roughly 9–12 days after the initial contact. Consequently, observable lice typically appear within one to two weeks of infestation.
How many days after infestation do lice appear? - in detail
The period between the moment a head‑lice egg is deposited on a scalp and the emergence of a mobile insect is typically 7–10 days. Female lice lay eggs (nits) close to the hair shaft; each egg requires about 7 days at normal body temperature to hatch. The newly emerged nymph resembles an adult but is smaller and unable to reproduce; it reaches full size and sexual maturity after an additional 5–7 days.
Consequently, a person may first notice itching or see live lice roughly two weeks after the initial contact with an infested individual. The timeline can be summarized:
- Egg deposition: immediate after a female attaches to the host.
- Incubation: 7 days for the egg to develop and hatch.
- Nymph development: 5–7 days to become an adult capable of laying eggs.
- First visible infestation: 12–14 days after the original exposure.
Factors that can modify these intervals include ambient temperature (higher temperatures accelerate development) and the host’s hair length (short hair may allow earlier detection). Routine inspection of the scalp and careful combing with a fine‑toothed lice comb are the most reliable methods for confirming the presence of live insects during this window.