How do lice develop on a child's head? - briefly
Female head lice lay eggs (nits) on hair close to the scalp; the eggs hatch in 7–10 days, and the nymphs become reproductive adults after an additional 7–10 days, completing the life cycle in roughly two weeks. Mobile lice transfer to another child through direct head-to-head contact, perpetuating the infestation.
How do lice develop on a child's head? - in detail
Lice infestation on a child’s scalp begins when a fertilized female deposits eggs (nits) near the scalp surface. Each egg is cemented to a hair shaft with a sticky protein, making it difficult to dislodge. The incubation period lasts approximately 7–10 days, after which the nymph emerges.
The newly hatched nymph resembles a miniature adult but lacks reproductive capability. It undergoes three molts over a span of 9–12 days, each molt increasing its size and mobility. Upon reaching adulthood, the insect can survive for about 30 days on the host, feeding several times daily on blood. An adult female produces 6–10 eggs per day, continuing the cycle as long as suitable conditions persist.
Key factors that facilitate the cycle include close head-to-head contact, shared combs or hats, and a warm, humid environment that favors egg adhesion and nymph development. Hair length influences detection; longer strands provide more surface area for egg placement, while short hair may reduce the number of viable attachment sites.
Detection relies on visual identification of nits within 1 cm of the scalp, appearing as tiny, oval, white or gray structures. Live lice are translucent to tan, approximately 2–4 mm long, and move rapidly when disturbed.
Effective control measures combine mechanical removal and chemical treatment. A fine-toothed nit comb, used on wet hair with a suitable conditioner, can extract both eggs and insects. Over-the-counter pediculicides containing permethrin or pyrethrin, applied according to label instructions, kill active lice but may not affect all eggs; a second application after 7–10 days targets newly hatched nymphs.
Environmental decontamination involves washing clothing, bedding, and personal items in hot water (≥ 60 °C) or sealing them in plastic bags for two weeks to interrupt the life cycle. Regular inspection of the scalp, especially after known exposure, helps prevent re‑infestation.