How long after infection do lice appear? - briefly
Lice become noticeable roughly 7–10 days after exposure, when eggs hatch and nymphs emerge. Adult insects can be seen a few days later as the nymphs mature.
How long after infection do lice appear? - in detail
Lice become visible on the host typically within 7‑10 days after the eggs (nits) hatch. The female adult deposits 6‑10 eggs per day, attaching them to hair shafts close to the scalp. Each egg requires about 8‑9 days to develop; this period is called the incubation phase. When the nymph emerges, it resembles an adult but is smaller and must feed on blood to mature. The nymphal stage lasts another 5‑7 days, during which the insect molts three times before reaching adulthood.
Consequently, the first signs—itching, a sensation of movement, or the appearance of live insects—generally appear after roughly two weeks from the initial contact with an infested person or contaminated object. Factors that can shorten or lengthen this timeline include:
- Host temperature: higher scalp warmth accelerates development.
- Hair length and density: longer, thicker hair provides more surface for eggs, potentially increasing the number of hatchlings.
- Individual immune response: heightened irritation may cause earlier detection.
Detectable nits are often seen within the first week, but they remain translucent and can be mistaken for hair debris until they darken after the embryo dies. Therefore, thorough examination of the scalp and hair, especially behind the ears and at the nape, is essential for early identification.
Prompt treatment should begin once live lice or viable nits are confirmed. Effective measures include:
- Application of a pediculicide approved for the age group.
- Mechanical removal of nits using a fine-toothed comb.
- Re‑treatment after 7‑10 days to eliminate any newly hatched nymphs that survived the initial application.
Understanding the precise timeline from egg deposition to visible infestation enables timely intervention and prevents further spread.