What do lice on a human head feed on? - briefly
Head lice survive by piercing the scalp and drinking human blood. They must feed every few hours to maintain their metabolism and complete their life cycle.
What do lice on a human head feed on? - in detail
Head lice (Pediculus humanus capitis) survive by ingesting human blood. Their mouthparts form a piercing‑sucking apparatus that penetrates the scalp skin to reach a capillary. Each bite delivers a small volume of plasma and erythrocytes, providing the protein, iron, and lipids required for growth and reproduction.
Adult females consume blood several times a day, typically every 3–5 hours, to support egg production. Nymphs feed less frequently, beginning a few hours after hatching and increasing the interval as they mature. The blood meal supplies:
- Hemoglobin and other proteins for tissue synthesis
- Iron for enzymatic processes and egg development
- Lipids for membrane formation and energy storage
During a single feeding event, a louse extracts roughly 0.5–1.0 µL of blood, enough to sustain its metabolism for a few hours. Repeated meals are essential; deprivation for more than 24 hours leads to mortality.
The nutritional dependence on human blood limits lice to the scalp environment, where temperature, humidity, and host availability remain optimal. Their feeding behavior causes localized irritation, minor inflammation, and, in severe infestations, secondary bacterial infection due to scratching.