How is the presence of lice checked? - briefly
Inspection uses a fine-tooth comb or magnifying device to separate hair and examine the scalp for live insects and attached nits near the hair shaft. Presence is confirmed when at least one viable louse or an egg within a centimeter of the scalp is detected.
How is the presence of lice checked? - in detail
Detecting a head‑lice infestation requires systematic examination of the scalp, hair shafts, and surrounding skin. The process begins with a thorough visual assessment, followed by mechanical combing, and, when necessary, laboratory verification.
The visual assessment involves parting the hair in sections of 2–3 cm, starting at the crown and moving outward. Inspect each section under bright lighting, focusing on the nape, behind the ears, and the hairline. Look for live insects, which appear as small, grayish‑brown bodies about the size of a sesame seed, and for nits—tightly adhered oval structures that are typically yellow‑white to brown and located within 1 cm of the scalp. Presence of nits close to the scalp indicates recent oviposition, while nits farther away suggest older infestations.
Mechanical combing enhances detection accuracy. Use a fine‑tooth (0.2 mm) lice comb on dry hair, moving from the scalp outward in a single, continuous stroke. After each stroke, wipe the comb on a white surface and examine for attached lice or nits. Repeat the process for all sections, re‑wetting hair if necessary to improve grip. Wet combing—hair soaked in a conditioner‑water mixture—reduces hair slip and increases the likelihood of capturing specimens.
Supplementary tools increase reliability. A handheld magnifying lens (10×–15×) allows close inspection of suspected nits, differentiating them from hair debris. A dermatoscope or digital microscope can capture high‑resolution images, facilitating documentation and expert review. Adhesive tape tests, wherein transparent tape is pressed to the scalp and examined under magnification, can reveal hidden nits in dense hair.
If visual and combing methods yield ambiguous results, a specimen can be sent to a laboratory for microscopic confirmation. A small sample of hair containing suspected nits is placed on a slide, stained, and examined at 100×–400× magnification to verify species and developmental stage. Molecular techniques such as PCR are reserved for research or epidemiological investigations and are not routine for clinical diagnosis.
Professional evaluation is advisable for schools, childcare facilities, and households with recurrent cases. Trained personnel should conduct examinations at the onset of symptoms and repeat them weekly for at least three weeks to ensure eradication. Parents and caregivers can perform home checks using the described methods, but any uncertainty warrants referral to a health professional.