How do lice appear on an adult's head? - briefly
Lice reach an adult’s scalp primarily through head‑to‑head contact with an infested person or by sharing personal items such as hats, combs, or pillows that contain viable nits. Once a few viable eggs hatch, the emerging insects spread rapidly across the hair shafts.
How do lice appear on an adult's head? - in detail
Lice reach an adult’s scalp primarily through direct head‑to‑head contact. When an infested person brushes or combs their hair, live nits or adult insects detach and cling to the hair shafts of the other individual. Shared personal items—combs, hats, scarves, pillows, or hair accessories—can also transfer eggs or nymphs, especially if the objects have not been cleaned or disinfected.
The life cycle facilitates rapid colonization. An adult female lays 5‑10 eggs (nits) per day, attaching them firmly to hair near the scalp. Eggs hatch in 7‑10 days, releasing nymphs that mature into reproductive adults within another 7‑10 days. This short developmental period allows a small initial transfer to expand into a noticeable infestation within two weeks.
Risk factors increase the likelihood of acquisition: crowded living conditions, frequent close contact in schools or workplaces, and inadequate personal hygiene practices that leave hair and scalp uncleaned for extended periods. Dense or long hair provides more surface area for eggs to attach, enhancing the chance of successful colonization.
Detection relies on visual inspection. Adult lice are 2‑3 mm long, gray‑brown, and move quickly across hair shafts. Nits appear as oval, whitish shells cemented at an angle to the hair shaft, typically within 1 cm of the scalp. Systematic combing with a fine‑toothed lice comb, performed on dry hair, reveals both live insects and attached eggs.
Preventive measures focus on breaking the transmission chain: avoid head contact with infested individuals, do not share hair care tools, and regularly wash personal items at temperatures above 55 °C or disinfect them with appropriate solutions. Prompt treatment of an identified case—using approved pediculicides or manual removal of nits—reduces the reservoir of lice and prevents further spread.