What causes lice in hair? - briefly
Head lice infestations occur when live insects or their eggs move from an infested person's scalp to another's through direct head‑to‑head contact or shared items such as combs, hats, or bedding. The parasites feed on human blood and reproduce quickly, enabling rapid spread.
What causes lice in hair? - in detail
Head lice (Pediculus humanus capitis) infest the scalp when female insects lay eggs (nits) on hair shafts close to the skin. The eggs hatch within seven to ten days, releasing nymphs that mature in another week. The primary mechanism of spread is direct head‑to‑head contact, which transfers live lice or nits from one person to another. Situations that increase such contact—classroom activities, sports teams, camps, and shared transportation—raise the likelihood of infestation.
Secondary pathways involve indirect transfer through personal items that have recently contacted an infested scalp. Comb, brush, hat, helmet, hair ties, pillowcases, and upholstered furniture can retain viable lice for a limited time. Though lice can survive off the host for up to 48 hours, transmission through objects is considerably less efficient than direct contact.
Environmental and behavioral factors also contribute:
- High population density, especially among children aged 3‑11, creates frequent close contact.
- Poor hair hygiene does not cause infestation; lice survive equally well on clean or dirty hair.
- Crowded living conditions and limited access to treatment resources increase persistence of outbreaks.
- Use of shared grooming tools in schools, daycare centers, or sports facilities facilitates spread.
Biological traits of the parasite support rapid propagation. Adult females lay 6‑10 eggs per day, each attached firmly to the hair cuticle with a cement-like substance. Nits become resistant to removal once the cement hardens, making detection and mechanical control difficult. Lice are attracted to the warmth and carbon dioxide emitted by the scalp, which guides them to suitable feeding sites.
In summary, the direct transfer of live insects during close head contact is the dominant cause of scalp infestation, supplemented by occasional transmission via contaminated personal items and amplified by crowded environments and limited treatment access. Effective prevention focuses on minimizing head‑to‑head contact, avoiding the sharing of hair accessories, and promptly treating identified cases to interrupt the life cycle.