How long does it take for lice to multiply on the head? - briefly
A female head louse can lay up to 10 eggs within a week, and the eggs hatch in about 7‑10 days, so the infestation can double in roughly two weeks. By the end of the second week after initial contact, noticeable numbers of nymphs and adults are typically present.
How long does it take for lice to multiply on the head? - in detail
Lice reproduce rapidly on a human scalp. An adult female can begin laying eggs within five to seven days after hatching. Each day she deposits five to ten nits, which are glued to hair shafts near the scalp. The incubation period for a nit lasts seven to ten days before the embryo emerges as a nymph.
The nymph undergoes three molts before reaching full maturity. Each molt requires roughly two to three days, so a nymph becomes an adult in about six to nine days after hatching. Consequently, a single adult can generate a new generation in approximately two weeks.
Population growth follows an exponential pattern. Assuming optimal conditions—average temperature around 30 °C, adequate blood supply, and no treatment—a mature female laying eight eggs per day can produce 56 eggs in a week. If half of those hatch and survive to adulthood, the colony can double its size every four to five days.
Typical timeline for a noticeable infestation:
- Day 0: Introduction of one adult female.
- Days 5‑7: First egg‑laying period begins.
- Days 12‑17: First batch of nymphs matures into adults.
- Days 19‑24: Second generation of eggs appears, increasing head‑lice count dramatically.
Factors that accelerate multiplication include warm, humid environments, dense hair, and frequent head‑to‑head contact. Conversely, low temperatures, regular combing with a fine‑toothed lice comb, and prompt treatment interrupt the cycle and reduce reproductive speed.
In practice, an untreated head can host several hundred lice within three weeks of the initial infestation, making early detection and immediate intervention essential to prevent exponential growth.