How do lice bite people? - briefly
Lice use their sharp mandibles to pierce the skin and inject saliva that contains anticoagulants, creating a tiny puncture that triggers itching. The bite is superficial, allowing the insect to feed on a small amount of blood from the scalp.
How do lice bite people? - in detail
Lice attach to the skin using their claws, positioning the head near a hair shaft or body hair. The mouthparts consist of a slender, needle‑like labium that houses a pair of mandibles and a maxilla. These structures pierce the epidermis, creating a minute incision that reaches the superficial dermis where capillary blood vessels lie.
During feeding, the louse inserts its proboscis into the wound and secretes a cocktail of anticoagulant proteins, primarily apyrase and other salivary enzymes. These substances prevent blood clotting, allowing a steady flow of plasma and erythrocytes into the feeding canal. The insect draws the fluid through a muscular pump, ingesting up to 0.5 µL of blood per bite, depending on species and host condition.
The feeding cycle proceeds as follows:
- Attachment: Claws grasp the hair shaft; body aligns with skin surface.
- Penetration: Labium and mandibles breach the epidermis.
- Saliva injection: Anticoagulants are released to keep blood fluid.
- Ingestion: Muscular action draws blood into the gut.
- Withdrawal: Mouthparts retract, leaving a tiny puncture that may itch or become inflamed.
Repeated bites cause localized irritation because the host’s immune system reacts to the foreign proteins in the saliva. Histamine release leads to redness, swelling, and the characteristic itching sensation. In severe infestations, cumulative blood loss is negligible, but secondary bacterial infection can arise from scratching the irritated sites.
Understanding this feeding mechanism clarifies why lice are obligate blood feeders and why control measures focus on disrupting attachment, preventing penetration, or neutralizing salivary anticoagulants.