Lice on a child's head: where do they come from? - briefly
Head lice spread mainly through direct head‑to‑head contact with an infested child, a common occurrence in schools and daycare settings. They can also be transmitted indirectly via personal items such as combs, hats, or bedding that have recently touched an infected scalp.
Lice on a child's head: where do they come from? - in detail
Head lice (Pediculus humanus capitis) are tiny, wing‑less insects that live on the scalp and feed on human blood. An adult measures about 2–3 mm, can survive up to 30 days on a host, and reproduces rapidly.
The parasite’s development proceeds through three stages. Eggs, called nits, are glued to hair shafts within 1 mm of the scalp and hatch in 7–10 days. Emerging nymphs resemble smaller adults and require an additional 9–12 days of feeding before reaching maturity. Once fertile, an adult female lays 6–10 eggs per day for up to three weeks.
Transmission occurs primarily through direct head‑to‑head contact, which is common during play, sports, or classroom activities. Secondary routes include sharing personal items such as combs, hairbrushes, hats, helmets, or headphones. Fomites such as bedding or upholstered furniture can harbor nits, but transmission via these surfaces is infrequent because nits require close proximity to the scalp to hatch.
Incidence peaks among children aged 3–11 years, especially in preschool and elementary settings where close contact is routine. Outbreaks are more likely in environments with high density, limited supervision of personal hygiene, and frequent exchange of headgear or accessories.
Key risk factors:
- Regular participation in group activities that involve head contact.
- Lack of routine scalp inspection.
- Use of shared grooming tools without disinfection.
- Presence of an untreated case within the household or school.
Preventive actions:
- Prohibit sharing of hats, hair accessories, and personal grooming devices.
- Conduct weekly visual checks of hair and scalp, focusing on the nape and behind the ears.
- Wash potentially contaminated items (combs, pillowcases, hats) in hot water (≥ 50 °C) and dry on high heat.
- Maintain short hair where feasible, as shorter lengths reduce the surface area for egg attachment.
Effective treatment options include:
- Over‑the‑counter pediculicides containing 1 % permethrin or 0.5 % pyrethrins, applied according to label instructions.
- Prescription agents such as 0.5 % malathion, 0.05 % ivermectin lotion, or oral ivermectin for resistant cases.
- Mechanical removal using fine‑toothed nit combs after applying a conditioner to immobilize lice.
- Repeat treatment 7–10 days after the initial application to eliminate newly hatched nymphs.
Prompt identification, immediate removal of the insects, and thorough cleaning of personal items interrupt the life cycle and prevent re‑infestation.