How to know when lice appeared? - briefly
Check the hair and scalp for live nits firmly attached near the roots and for active biting signs such as itching, redness, or small blood spots. The observation of moving insects confirms a recent lice infestation.
How to know when lice appeared? - in detail
Detecting a fresh lice infestation requires careful observation of the scalp and hair. The first indicator is the presence of live insects. Adult lice are about 2–3 mm long, grayish‑brown, and move quickly when the hair is lifted. Nymphs, or “baby lice,” appear a few days after eggs hatch and are slightly smaller but still visible to the naked eye.
The second sign is the appearance of nits. Nits are oval, cemented to the hair shaft close to the scalp. Viable nits are firmly attached; a gentle tug will not dislodge them. Freshly laid nits are white or pale yellow; after a few days they turn tan or brown. A concentration of nits within ¼ inch of the scalp strongly suggests a recent infestation.
Itching is a common symptom, but it often develops only after the scalp becomes sensitized to lice saliva. Early-stage itching may be mild and intermittent, whereas prolonged exposure leads to more intense, localized irritation. Scratching can cause secondary skin lesions, which may be mistaken for other conditions.
Physical examination can be enhanced by the following steps:
- Part the hair into sections of 1–2 cm width.
- Use a fine‑toothed lice comb on wet, conditioned hair.
- Examine the comb after each pass for live lice, nymphs, or nits.
- Inspect the scalp under good lighting; a magnifying lens can aid detection of small nymphs.
Laboratory confirmation is rarely necessary, but a sample of collected insects can be examined under a microscope to verify species and developmental stage. This confirms whether the infestation is recent (presence of nymphs and fresh nits) or chronic (large proportion of empty egg shells).
Timing can be inferred from the life cycle: lice hatch from eggs in 7–10 days, mature to adults within another 7 days, and begin laying new eggs. Therefore, finding a mixture of live adults, nymphs, and freshly laid nits indicates that the infestation began within the past two weeks. Absence of nymphs and presence only of empty shells suggest an older, possibly resolved situation.
In summary, reliable detection of a new lice outbreak relies on visual identification of live insects, assessment of nit location and color, evaluation of itching patterns, systematic combing, and, when needed, microscopic verification. These methods together provide a clear picture of when the infestation started.