How do lice appear in the head? - briefly
Infestation begins when adult female lice attach to hair near the scalp and lay eggs (nits) on the strands. The hatching nymphs feed on blood and multiply, spreading the colony throughout the head.
How do lice appear in the head? - in detail
Lice infest a person’s scalp when viable nymphs or adult females are transferred from an infected source to the hair of a new host. The transfer occurs primarily through direct head‑to‑head contact; the insects cling to hair shafts and crawl onto the recipient’s scalp within seconds. Indirect transmission is possible when hair accessories, hats, pillows, or brushes that have recently housed live lice are shared, although the risk is lower because lice survive only 24–48 hours off a human host.
The infestation process follows the species’ life cycle. After a fertilized female deposits 6–10 eggs (nits) near the base of a hair shaft, each egg hatches in 7–10 days. Emerging nymphs undergo three molts, each lasting 3–4 days, before reaching reproductive maturity. The entire cycle from egg to adult takes approximately 2–3 weeks, during which a single female can lay up to 300 eggs, rapidly increasing the population on the scalp.
Factors that facilitate the initial appearance of lice include:
- Close, prolonged contact with an infested individual (e.g., classroom, sports teams, camps).
- Shared personal items that contact hair or scalp.
- Crowded living conditions that increase the frequency of head contact.
- Warm, humid environments that support lice survival and reproduction.
Once established, lice feed on blood several times per day, causing itching and irritation. The characteristic signs—visible adult lice, translucent nits attached to hair shafts, and a “scratchy” scalp—appear within a few weeks after the first transfer.
Effective control requires removal of live insects and their eggs, combined with measures to prevent re‑exposure. This includes thorough combing with a fine‑toothed lice comb, washing or isolating contaminated items for at least 48 hours, and avoiding head‑to‑head contact until the infestation is cleared.