Why do lice appear on hair? - briefly
Lice infest hair when they are transferred from an infested person or contaminated items, as the insects require human scalp warmth and blood to survive and reproduce. Crowded environments, close personal contact, and inadequate hygiene increase the likelihood of transmission.
Why do lice appear on hair? - in detail
Lice survive by feeding on human blood; they require a warm, moist environment that a scalp provides. The head offers a stable temperature around 34 °C and a protective layer of hair where the insects can cling, lay eggs, and avoid external disturbances.
Transmission occurs primarily through direct head‑to‑head contact, which transfers adult insects and nits from one person to another. Secondary routes include sharing combs, hats, helmets, or bedding that have become contaminated. Contact with infested environments, such as schools or camps, raises the likelihood of acquisition.
Factors that increase the risk of infestation are close physical proximity, high humidity, and the presence of a dense hair coat. Poor personal hygiene may contribute but does not alone cause an outbreak; lice can thrive on clean hair as long as the conditions above are met.
The life cycle consists of three stages. Eggs (nits) are cemented to hair shafts near the scalp, where they incubate for 7–10 days. Upon hatching, nymphs emerge, feed, and molt three times over a period of about 10 days before reaching adulthood. Adult lice live up to 30 days on a host, producing 5–10 eggs per day, which ensures rapid population growth if unchecked.
Control measures involve early detection, removal of nits with a fine‑toothed comb, and application of approved pediculicidal agents. Regular cleaning of personal items, avoidance of sharing headgear, and routine scalp inspections in high‑risk settings reduce the probability of recurrence.