How do lice appear on the body? - briefly
Lice infest the scalp when adult females lay eggs (nits) that adhere to hair shafts and hatch, allowing the newly emerged nymphs to feed on blood and multiply rapidly. Transmission occurs primarily through direct head-to-head contact or sharing personal items such as combs, hats, or pillows.
How do lice appear on the body? - in detail
Lice become established on a human host through a sequence of biological steps that begin with the transfer of viable eggs or adult insects from an infected source. The most common routes are:
- Direct head‑to‑head contact, which moves adult head lice or newly hatched nymphs onto a clean scalp.
- Contact with personal items such as combs, hats, hairbrushes, pillowcases, or clothing that have retained viable eggs (nits) or live lice.
- For body lice, prolonged wearing of contaminated clothing or bedding allows insects to move from the fabric to the skin.
Once on the host, a female adult deposits her eggs near the base of hair shafts or in the seams of clothing, securing each nit with a cement‑like substance that resists removal. The eggs hatch in 7–10 days, releasing nymphs that immediately begin feeding on blood. Nymphs undergo three molts over 9–12 days, after which they become reproductive adults. An adult female can lay 6–10 eggs per day, leading to exponential population growth if unchecked.
Key biological factors that facilitate infestation include:
- Temperature and humidity – optimal conditions (30 °C, 70 % relative humidity) accelerate development and increase survival rates.
- Host grooming habits – infrequent hair washing or clothing changes provide a stable environment for eggs and nymphs.
- Social behavior – activities that involve close physical proximity (e.g., school settings, shared living quarters) raise transmission risk.
Control measures target each stage of the life cycle: mechanical removal of nits, topical insecticides that kill adults and nymphs, and regular laundering of clothing and bedding at temperatures above 60 °C to eradicate eggs. Consistent application of these strategies interrupts the colonization process and prevents re‑infestation.