How can lice be detected on a person? - briefly
Direct visual examination of the scalp, especially the neck and behind the ears, identifies adult lice and their attached eggs («nits») on hair shafts; employing a fine‑tooth comb on damp hair can collect additional specimens for definitive confirmation.
How can lice be detected on a person? - in detail
Detecting head‑lice infestations requires systematic examination of the scalp and hair. Visual inspection involves parting the hair in sections as small as one centimeter, then scanning the root area for live insects, nymphs, or viable eggs. Live lice appear as gray‑brown, six‑legged bodies ranging from 2 to 5 mm; nymphs are smaller and translucent. Eggs, commonly called nits, attach firmly to the hair shaft within 1 cm of the scalp and display a characteristic oval shape and a white or yellowish hue.
A fine‑tooth comb, often marketed as a “lice comb,” enhances detection. The comb’s teeth, spaced at 0.2 mm, are drawn through each hair section from scalp to tip. After each pass, the comb is inspected against a contrasting background; any captured insects are counted and recorded. Repeating the process across the entire head improves sensitivity, especially in early infestations where few lice are present.
Magnification tools increase reliability. Handheld loupes offering 2–4× magnification allow identification of minute nymphs and early‑stage eggs that might be missed by the naked eye. When available, a stereomicroscope provides detailed visualization, facilitating differentiation between viable eggs and empty shells.
Commercial detection kits employ adhesive tape or specialized dyes. The tape method applies a small strip to the scalp, then lifts it for microscopic examination. Dye‑based kits use a non‑toxic solution that stains the exoskeleton of lice, rendering them more visible under normal lighting.
Molecular techniques, such as polymerase chain reaction (PCR), confirm the presence of lice DNA from hair or skin samples. PCR offers high specificity but is typically reserved for research or cases where conventional methods yield ambiguous results.
Detection methods summary
- Direct visual inspection with systematic hair sectioning.
- Fine‑tooth combing across the entire scalp.
- Use of magnifying lenses or stereomicroscopes.
- Adhesive‑tape or dye‑based commercial kits.
- PCR analysis for definitive identification.
Combining at least two approaches—visual inspection and combing, supplemented by magnification when necessary—maximizes detection accuracy and supports timely treatment decisions.