How can the presence of lice in people be determined? - briefly
A thorough examination of the scalp and hair, preferably with a fine‑tooth comb, reveals live insects and attached nits; magnification tools such as a dermatoscope can enhance detection. Laboratory analysis of collected specimens confirms species identification when necessary.
How can the presence of lice in people be determined? - in detail
Detecting a lice infestation in a person relies on visual inspection, tactile assessment, and, when necessary, laboratory confirmation.
A trained examiner examines the scalp, hair, and body hair under adequate lighting. Live lice are identified by their size (2–4 mm), gray‑brown coloration, and active movement. Nits (lice eggs) appear as oval, white or yellowish structures firmly attached to the hair shaft at a 45‑degree angle, usually within 1 cm of the scalp.
Physical clues support diagnosis: persistent itching, especially after bathing, and the presence of small blood spots or crusted lesions on the skin.
When visual evidence is ambiguous, the following techniques enhance detection:
- Fine‑toothed combing: A lice comb with 0.2‑mm spacing is drawn through wet hair from scalp to ends; each pass is examined for lice or nits. Repeating the process several times increases capture rates.
- Magnification: Handheld lenses or stereomicroscopes (up to 10× magnification) reveal nits embedded close to the scalp that may be missed by the naked eye.
- Adhesive tape sampling: Transparent tape applied to hair shafts and examined under a microscope can uncover eggs and immature stages.
- Molecular testing: Polymerase chain reaction (PCR) assays target lice DNA from hair or skin scrapings, providing definitive identification, particularly in epidemiological investigations.
Treatment decisions depend on confirming the presence of viable lice rather than merely detecting empty shells. Accurate identification prevents unnecessary medication and guides appropriate interventions such as topical pediculicides, manual removal, or environmental decontamination.