How do lice form in a person? - briefly
Lice appear when adult female insects lay eggs (nits) on hair shafts close to the scalp, and the hatched nymphs feed on blood, multiplying rapidly through successive molts. Transmission occurs via direct head-to-head contact or sharing contaminated personal items such as combs, hats, or bedding.
How do lice form in a person? - in detail
Lice infestations begin when a female adult deposits her eggs on the hair shaft close to the scalp. Each egg, known as a nit, is cemented with a proteinaceous glue that resists removal. After approximately seven to ten days, the nit hatches, releasing a nymph that resembles an adult but is smaller and cannot yet lay eggs. The nymph feeds on blood three to five times a day, gaining size and molting through three successive stages before reaching maturity. An adult female lives about three weeks and can lay up to eight eggs per day, rapidly increasing the population if untreated.
Key biological factors that enable colonization:
- Warmth and moisture – the scalp provides an optimal temperature (33–35 °C) and humidity for lice metabolism and egg development.
- Direct head-to-head contact – transmission occurs most efficiently when hair brushes against another person’s hair, allowing mobile lice to crawl onto a new host.
- Crowded environments – close proximity in schools, camps, or households raises the likelihood of contact and exchange of lice.
- Hair length and texture – longer hair offers more surface area for egg attachment; certain hair types may facilitate easier movement of lice.
The life cycle proceeds as follows:
- Egg (nit) stage: 7–10 days; firmly attached to hair.
- Nymph stage: 3–4 days per molt; three molts total.
- Adult stage: 7–10 days; capable of reproduction.
Population growth is exponential: a single fertilized female can generate 300–500 lice within a month under favorable conditions. Continuous feeding on blood causes scalp irritation, leading to scratching, secondary infection, and increased spread through contaminated personal items such as combs or hats, although direct contact remains the primary route.
Effective control requires disrupting this cycle by removing nits, treating the scalp with approved pediculicides, and preventing re‑infestation through regular inspection and avoidance of head-to-head contact.