What do lice cause? - briefly
Lice infestations cause intense itching and skin irritation, and the resulting scratching can lead to secondary bacterial infections or allergic reactions. In severe cases, especially with large numbers of head lice, they may cause anemia due to blood loss.
What do lice cause? - in detail
Lice are obligate blood‑feeding insects that produce several direct and indirect health effects.
The most immediate consequence is intense pruritus caused by the bite’s mechanical irritation and the injection of saliva. Repeated scratching often leads to excoriation, which creates entry points for bacterial pathogens such as Staphylococcus aureus or Streptococcus pyogenes. Resulting skin infections may develop into impetigo, cellulitis, or erythematous dermatitis.
Allergic responses to lice saliva can manifest as papular urticaria or chronic eczema, especially in individuals with heightened sensitivity. In severe infestations, prolonged blood loss may cause measurable iron deficiency anemia, although this outcome is uncommon with head lice and more frequent with body lice.
Body lice (Pediculus humanus corporis) serve as vectors for several serious infections:
- Rickettsia prowazekii – epidemic typhus
- Borrelia recurrentis – relapsing fever
- Bartonella quintana – trench fever
These pathogens are transmitted when infected lice are crushed or when contaminated feces enter skin lesions.
Beyond medical effects, infestations generate psychosocial consequences. Visible nits or adult insects provoke embarrassment, lead to social stigma, and may cause school or work absenteeism.
Effective control requires prompt identification, appropriate pediculicidal treatment, and measures to eliminate reservoirs such as personal clothing, bedding, and shared items. Regular combing, laundering at temperatures above 60 °C, and environmental decontamination reduce recurrence risk.