What causes lice to appear in the head? - briefly
Head lice infestations arise from direct head‑to‑head contact with an infested individual or from sharing personal items such as combs, hats, or bedding. Warm, humid conditions and close‑quarter environments increase the probability of transmission.
What causes lice to appear in the head? - in detail
Head lice infestations arise when Pediculus humanus capitis adults or nymphs come into direct contact with hair shafts. Transmission occurs primarily through head‑to‑head contact, which enables the insect to crawl from one scalp to another. Sharing personal items such as combs, hats, helmets, hair accessories, or bedding can also facilitate movement of lice, especially when these objects are placed on a contaminated head.
Factors increasing the likelihood of an outbreak include:
- Close‑quarters environments where children interact frequently (schools, day‑care centers, camps).
- Insufficient cleaning of shared equipment or surfaces that may retain viable eggs (nits).
- Overcrowded living conditions that limit personal space and reduce opportunities for regular grooming.
- Lack of awareness about the life cycle: an adult female lays 5–10 eggs per day, attaching them to hair near the scalp; eggs hatch in 7–10 days, and the cycle repeats within 2–3 weeks.
The biology of the parasite contributes to persistence. Lice require a constant temperature of 30–34 °C, provided by the human scalp, and cannot survive more than 24 hours off a host. Eggs are cemented to the hair shaft with a proteinaceous glue, making manual removal difficult without specialized tools. Resistance to common insecticidal shampoos has emerged, reducing the effectiveness of some chemical treatments.
Preventive measures focus on reducing opportunities for direct contact and limiting the availability of contaminated objects. Regular inspection of hair, especially in high‑risk groups, allows early detection. When an infestation is identified, thorough combing with a fine‑toothed lice comb, washing of personal items in hot water (≥ 50 °C), and isolation of infested individuals for the duration of the treatment cycle diminish the chance of re‑infestation.