What happens on the head when lice are present? - briefly
Lice feeding on the scalp causes itching and often leads to red, irritated spots where the insects bite and lay eggs. Their presence can also result in a visible nits (egg shells) attached to hair shafts.
What happens on the head when lice are present? - in detail
An infestation of head‑lice triggers a cascade of physiological and visible changes on the scalp. Adult insects attach to hair shafts near the skin and use their mouthparts to pierce the epidermis, drawing small amounts of blood several times a day. Each feeding episode introduces saliva that contains anticoagulant proteins, which provoke a localized immune response. The reaction manifests as redness, swelling, and a persistent pruritic sensation that intensifies after prolonged feeding periods.
Repeated scratching, driven by the itch, damages the stratum corneum and can produce micro‑abrasions. These breaches serve as entry points for opportunistic bacteria such as Staphylococcus aureus or Streptococcus pyogenes, potentially leading to secondary folliculitis or impetigo. Inflammation may also cause the scalp to become oily or dry, altering the natural sebum balance and creating an environment that favors further lice activity.
The life cycle of the parasite contributes to the observable signs. Female lice lay oval, white eggs (nits) firmly glued to the proximal portion of each hair shaft, typically within 1 cm of the scalp. Nits are attached by a cement‑like substance that hardens within minutes, making them resistant to removal by simple combing. After 7–10 days, nits hatch into nymphs, which resemble miniature adults and mature over another 9–12 days, perpetuating the infestation cycle.
Visible indicators include:
- Live insects, 2–4 mm long, gray‑brown in color, moving swiftly along hair shafts.
- Empty egg shells that remain attached after hatching, appearing as translucent, chalky specks.
- Small blood spots on hair or pillowcases, resulting from crushed lice or broken blood vessels.
Physiological stress from the feeding process can lead to mild anemia in severe, prolonged infestations, as each louse consumes approximately 0.5 µL of blood per day. Although rare, this effect underscores the importance of timely detection and treatment.
Effective management requires eradication of both live lice and their eggs, restoration of scalp integrity, and prevention of bacterial superinfection. Antiparasitic agents, thorough combing, and hygiene measures address the infestation, while topical antiseptics or antibacterial ointments treat any secondary skin lesions.