Lice on hair – how can they be detected?

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Lice on hair – how can they be detected? - briefly
A thorough scalp and hair examination for live insects and eggs attached near the root reveals an infestation. A fine‑tooth comb used on wet hair, with careful inspection of the comb and hair strands, confirms the presence of lice and nits.

Lice on hair – how can they be detected? - in detail
Detecting head‑lice infestations requires a systematic visual and tactile examination of the scalp and hair. The process begins with a thorough inspection under bright illumination, preferably with a handheld lamp or natural daylight. A magnifying device (10‑20×) enhances the ability to distinguish tiny insects and eggs from surrounding debris.
The primary indicators are:

Live adult lice, 2–4 mm in length, moving quickly across the hair shaft.
Nits (lice eggs) firmly attached to the hair cuticle, typically within 1 cm of the scalp; they appear as oval, yellow‑brown structures and do not detach easily when the hair is brushed.
Shells (empty nits) that are translucent and brittle.
Symptoms such as persistent itching caused by allergic reactions to lice saliva.

Effective detection methods include:

Fine‑tooth nit combing

Use a metal or plastic comb with 0.2‑0.3 mm spaced teeth.
Section hair into 1‑inch strands; comb from scalp outward, wiping the comb on a white tissue after each pass.
Repeat until no live lice or nits are observed in multiple passes.

Direct visual inspection

Separate hair with a finger or clip, examine each section against a light source.
Look for moving lice on the scalp or nits attached close to the root.
Document findings with a smartphone camera for later reference.

Adhesive tape sampling

Press clear medical tape onto a small area of hair near the scalp.
Inspect the tape under magnification; any adhered insects confirm presence.

Laboratory microscopy

Collect hair samples containing suspected nits.
Examine under a compound microscope (40‑100×) to verify egg morphology and viability.

Commercial detection kits

Some kits contain a specialized comb and a staining solution that highlights lice bodies, facilitating rapid identification.

Digital applications

Certain smartphone apps use the camera and AI algorithms to identify lice and nits in uploaded images, providing a secondary verification tool.

To reduce false positives, differentiate nits from dandruff, hair fibers, or product residues. Nits remain firmly attached; they cannot be easily dislodged by a gentle pull or a light brush. Dandruff flakes are loosely attached and often fall off when the hair is moved.
A reliable assessment protocol recommends:

Conducting an initial inspection in a well‑lit environment.
Performing at least three consecutive combing sessions, each spaced 24 hours apart, to capture newly hatched lice that may have emerged after the first pass.
Recording the number of live lice and viable nits; a count of any live lice confirms infestation, while the presence of several viable nits near the scalp warrants treatment.

Following detection, immediate implementation of appropriate eradication measures—mechanical removal, pediculicidal agents, or combination therapy—prevents further spread. Continuous monitoring for a minimum of two weeks ensures that the life cycle has been interrupted and that re‑infestation does not occur.