What are lice on the head? - briefly
Head lice are tiny, wingless insects that inhabit the scalp and consume human blood. They deposit eggs, called nits, which adhere to hair shafts and often cause itching and secondary skin irritation.
What are lice on the head? - in detail
Pediculus humanus capitis, commonly referred to as scalp lice, is a small, wing‑less ectoparasite that lives exclusively on the human head. Adult insects measure 2–3 mm, have a flattened body, and cling to hair shafts with clawed legs. Their primary function is to feed on blood from the scalp, which sustains growth and reproduction.
The life cycle consists of three distinct stages:
- Egg (nit) – oval, firmly attached to the hair close to the scalp; incubation lasts 7–10 days.
- Nymph – immature form that molts three times over 9–12 days; each molt increases size and feeding capacity.
- Adult – capable of laying up to 10 eggs per day; lifespan on a host ranges from 30 days to several weeks.
Clinical manifestations appear within 4–6 weeks after initial infestation and include:
- Persistent itching caused by allergic reactions to saliva.
- Visible nits attached to hair shafts, often near the crown.
- Small, reddish‑brown spots on the scalp where feeding has occurred.
Transmission occurs through direct head‑to‑head contact, sharing of combs, hats, or bedding. Indirect spread via fomites is less common but possible when items remain in close proximity to an infested scalp.
Diagnosis relies on visual inspection with a fine‑tooth comb or magnifying device. Identification of live lice or viable nits confirms infestation; empty shells alone are insufficient evidence.
Effective management options are:
- Topical pediculicides containing permethrin (1 %) or dimethicone (4 %). Application follows manufacturer instructions, with a repeat treatment after 7–10 days to eliminate newly hatched nits.
- Manual removal using a fine‑tooth nit comb after wetting hair with conditioner; repeated combing at 2‑day intervals for at least 10 days ensures complete eradication.
- Oral ivermectin for cases resistant to topical agents; dosage is weight‑adjusted and requires medical supervision.
Preventive measures include:
- Avoiding head contact during group activities.
- Regularly inspecting children’s hair, especially after school or camp.
- Washing clothing, bedding, and personal items at ≥ 60 °C or sealing them in plastic bags for two weeks to kill dormant stages.
Prompt identification and thorough treatment interrupt the reproductive cycle, preventing re‑infestation and minimizing discomfort.