What are lice and why do they appear? - briefly
Lice are tiny, wingless parasitic insects that inhabit human hair and feed on blood. They emerge when nits are transferred through direct contact or shared items and thrive in warm, humid conditions.
What are lice and why do they appear? - in detail
Lice are obligate ectoparasites belonging to the order Phthiraptera. The most common species affecting humans are the head louse (Pediculus humanus capitis) and the body louse (Pediculus humanus corporis). Adult females lay 6–10 eggs (nits) per day, attaching them firmly to hair shafts or clothing fibers. Nits hatch in 7–10 days, releasing nymphs that undergo three molts before reaching reproductive maturity. The life cycle, lasting 2–3 weeks, enables rapid population expansion under favorable conditions.
Factors that trigger infestations include:
- Close physical contact, especially among children in schools, daycare centers, or sports teams.
- Shared personal items such as combs, hats, scarves, or bedding.
- Overcrowded living environments where hygiene practices are compromised.
- Warm, humid climates that favor egg adhesion and nymph development.
- Lack of regular hair grooming or inspection, allowing early stages to remain unnoticed.
Transmission occurs when viable nits or mobile nymphs are transferred from one host to another. Adult lice cannot survive long off the human body; survival beyond 48 hours without a host is rare. Consequently, effective control focuses on direct removal of insects and their eggs, combined with environmental measures that eliminate residual contamination.
Recommended interventions comprise:
- Mechanical removal using fine-toothed combs applied to wet hair, repeated every 2–3 days for two weeks.
- Topical pediculicides containing permethrin 1 % or dimethicone, applied according to product instructions and followed by thorough combing.
- Laundering of contaminated textiles at ≥ 60 °C or sealing them in airtight bags for 2 weeks to kill dormant stages.
- Education of affected individuals and their contacts about avoidance of head-to-head contact and regular inspection.
Monitoring after treatment should continue for at least four weeks to detect recrudescence. Early detection and prompt eradication minimize the risk of secondary skin infections and reduce the social impact of outbreaks.