How can one become infected with lice from a person? - briefly
Lice are transmitted when a person’s hair touches another’s head or when personal items—combs, hats, pillows, or clothing—containing live insects or viable eggs are shared. Preventing such direct contact and regularly cleaning shared objects stops the spread.
How can one become infected with lice from a person? - in detail
Lice are obligate ectoparasites that require a living host for survival. Transmission occurs only when the insects or their eggs are physically transferred from one person to another.
Direct head‑to‑head contact is the most efficient route. When two scalps touch, adult lice and newly hatched nymphs can crawl onto the new host within seconds. The same mechanism applies to body lice, which move from the clothing of an infested individual to the garments of a close contact.
Sharing personal items creates an indirect pathway. Combs, brushes, hair clips, hats, scarves, helmets, pillowcases, blankets, towels, and upholstered furniture can harbor live lice or viable nits. A louse can survive off the human body for 24–48 hours; a nit can remain viable for up to a week under favorable conditions. Contact with any contaminated object during this period can result in infestation.
Crowded environments increase the likelihood of exposure. Schools, daycare centers, shelters, and prisons provide frequent opportunities for the required close contact or shared use of items. Body lice, in particular, thrive in situations where clothing is not regularly washed at temperatures above 130 °F (54 °C).
The life cycle reinforces transmission risk. Female lice lay 6–10 eggs per day, attaching them to hair shafts or fabric seams. Eggs hatch in 7–10 days, producing nymphs that reach maturity in another 9–12 days. Because nits are firmly glued, they can be transferred unintentionally when hair or clothing is brushed or laundered.
In summary, infestation results from:
- Direct scalp or body contact.
- Use of shared grooming tools or headwear.
- Contact with contaminated bedding, towels, or upholstered surfaces.
- Exposure in densely populated settings where personal items are frequently exchanged.
Preventive measures focus on eliminating these pathways: avoid sharing personal items, wash clothing and bedding at high temperatures, dry on a hot setting, and isolate suspected cases until treatment is completed.