What do lice do on a person's head? - briefly
Lice feed on blood by piercing scalp skin with their mouthparts, causing itching and irritation. Their movement and egg‑laying can lead to secondary infections if left untreated.
What do lice do on a person's head? - in detail
Head lice (Pediculus humanus capitis) inhabit the hair shafts and scalp of humans, where they perform several essential functions for their survival and propagation.
The insects feed exclusively on blood. They insert their mouthparts into the skin, pierce capillaries, and ingest small volumes of blood several times a day. This feeding causes localized irritation, redness, and itching as the host’s immune system reacts to the saliva injected during each bite.
Reproduction occurs on the host. A mature female lays 3–5 eggs (nits) per day, attaching each to a hair strand near the scalp with a cement-like substance. Eggs hatch after 7–10 days, releasing nymphs that undergo three molts over 9–12 days before reaching adulthood. The entire life cycle, from egg to adult, can be completed in about three weeks under favorable conditions.
Movement is limited to crawling. Lice cannot jump or fly; they travel by walking along hair shafts, using their claws to grasp each strand. This behavior confines them to the head region and requires close contact between individuals for transfer.
Population density increases as more females produce eggs, leading to a visible accumulation of nits along the hair shaft. A heavy infestation amplifies the host’s discomfort and raises the risk of secondary bacterial infection from scratching.
While head lice are not known to transmit serious pathogens, their presence can affect social and psychological well‑being, prompting treatment and preventive measures.