What are hair lice? - briefly
Hair lice are tiny, wingless insects (Pediculus humanus capitis) that inhabit the scalp and feed on human blood. They are transmitted primarily by direct head‑to‑head contact, causing itching and irritation.
What are hair lice? - in detail
Hair lice are small, wing‑less insects that inhabit the scalp and feed on human blood. Belonging to the order Phthiraptera, species Pediculus humanus capitis is the most common cause of infestation in humans. Adult lice measure 2–4 mm, have a flattened body, six legs with clawed tarsi for gripping hair shafts, and a coloration ranging from gray‑white to brown.
The life cycle consists of three stages: egg (nit), nymph, and adult. Females lay 6–10 eggs per day, attaching them to the base of hair strands with a cementing substance. Eggs hatch in 7–10 days, releasing nymphs that resemble miniature adults. Nymphs undergo three molts over 9–12 days before reaching reproductive maturity. The entire cycle from egg to egg‑laying adult lasts approximately 3 weeks under optimal conditions.
Transmission occurs through direct head‑to‑head contact, which is the primary route in schools and households. Indirect spread via personal items—combs, hats, pillows—is less common but possible when lice or nits are transferred to a new host. Infestations thrive in environments where close contact is frequent and hair hygiene practices are inadequate.
Clinical signs include:
- Persistent itching caused by allergic reactions to saliva.
- Visible live insects moving on the scalp or hair shafts.
- Small, oval, white or brownish nits attached firmly to hair near the scalp.
- Irritation or redness of the scalp, sometimes with secondary bacterial infection.
Diagnosis relies on visual inspection using a fine‑toothed comb or magnification. Examination should focus on the nape of the neck, behind the ears, and the crown, where lice concentrate. Confirmation requires finding live lice or viable nits within 1 mm of the scalp surface.
Effective treatment strategies involve:
- Topical pediculicides (e.g., permethrin 1 % or dimethicone) applied according to manufacturer instructions, repeated after 7–10 days to eliminate newly hatched nymphs.
- Manual removal of nits with a fine comb, performed every 2–3 days for two weeks.
- Environmental decontamination: washing bedding, clothing, and personal items in hot water (≥ 60 °C) or sealing them in plastic bags for two weeks.
- Education of contacts to prevent re‑infestation, including avoidance of head‑to‑head contact and regular screening of close associates.
Resistance to common insecticides has been documented; in such cases, alternative agents (e.g., ivermectin, malathion) or combination therapy may be required under medical supervision. Continuous monitoring after treatment ensures eradication and reduces the risk of recurrence.