How do lice spread to another person? - briefly
Lice spread primarily through direct head‑to‑head contact. Sharing objects that touch hair—hats, combs, hair accessories—can also transmit them.
How do lice spread to another person? - in detail
Lice are wing‑less insects that survive only on human blood. Transmission occurs primarily through physical contact that places an infected scalp in direct proximity to a susceptible one. The most efficient pathway is head‑to‑head interaction, where adult females or nymphs crawl from one hair shaft to another within seconds. This mode dominates in schools, day‑care centers, and sports teams where children frequently touch each other’s heads.
Secondary pathways involve shared objects that retain live lice or viable eggs for up to 48 hours. Items include:
- Combs, brushes, hair accessories, and hats.
- Pillows, blankets, and upholstered furniture.
- Caps, scarves, and helmets used by multiple users.
Lice cannot jump or fly; they move by clinging to hair fibers and crawling. Consequently, the likelihood of transfer from a contaminated surface depends on the duration of contact and the presence of viable eggs (nits) attached to the object. Eggs hatch within 7–10 days, producing mobile nymphs that can immediately seek a new host.
Environmental factors influence spread:
- Warm, humid conditions accelerate nymph development and increase activity.
- High infestation density raises the probability that an individual will encounter mobile insects during routine grooming.
- Overcrowded living conditions reduce personal space, enhancing direct contact opportunities.
Risk groups include preschool children, adolescents participating in contact sports, and individuals in communal housing. Personal hygiene alone does not prevent transmission, because lice thrive even on clean hair; the critical element is limiting close head contact and avoiding the exchange of contaminated personal items.
To interrupt the cycle, interventions focus on:
- Immediate identification of live insects and viable nits.
- Isolation of the affected individual for treatment duration.
- Thorough cleaning of shared objects—washing at >50 °C or sealing in plastic for two weeks.
- Education of caregivers and participants about the necessity of avoiding head contact and sharing hair accessories.
Understanding these mechanisms enables targeted control measures, reducing the chance of new infestations among susceptible populations.