Where do lice nits come from? - briefly
Lice nits are the eggs deposited by adult head lice on individual hair strands, usually close to the scalp. Female lice lay them directly while feeding, securing each egg with a sticky cement.
Where do lice nits come from? - in detail
Lice nits are the attached eggs of the human head‑louse, Pediculus humanus capitis. A fertilized female deposits each egg on a single hair shaft, usually within 1 cm of the scalp, where body heat promotes embryonic development. The egg is cemented with a proteinaceous glue that hardens within minutes, securing the nit until hatching, typically after 7–10 days.
Transmission occurs through direct contact and limited indirect routes. The most common pathways are:
- Head‑to‑head contact lasting several minutes.
- Sharing of personal items such as combs, brushes, hats, hair accessories, and scarves.
- Contact with recently used bedding, pillows, or upholstered furniture that has retained live nits.
Lice eggs do not survive long away from a living host. Once detached from the hair, the cement loses its adhesive properties, and the nit dries out, rendering it non‑viable within 24–48 hours. Consequently, objects that have not been in recent contact with an infested scalp are unlikely to harbor hatchable eggs.
Misconceptions persist that nits can hatch on clothing or in the environment without a host. In reality, embryogenesis requires the stable temperature and humidity provided by the scalp. Eggs found on clothing or in the home are generally empty shells or dead nits, not a source of new infestation.
Detection relies on visual inspection of the scalp and hair. Viable nits appear as oval, tan‑colored structures firmly attached to the hair shaft, often at a shallow angle. A fine‑toothed nit comb, passed from the scalp outward, removes both live nits and empty shells, reducing the chance of further development.
Effective control combines mechanical removal, appropriate topical treatments that target adult lice, and environmental hygiene measures such as washing bedding and personal items at 60 °C or sealing them in plastic bags for two weeks to prevent re‑infestation.