How do lice look on hair and what causes their appearance? - briefly
Adult head lice are 2–3 mm long, grayish‑brown, flattened insects with six legs that cling tightly to hair shafts, appearing as tiny moving specks or as oval, white nits attached near the scalp. Their appearance stems from infestation by Pediculus humanus capitis, transmitted via direct head‑to‑head contact or sharing contaminated personal items.
How do lice look on hair and what causes their appearance? - in detail
Lice are small, wing‑less insects measuring 2–4 mm in length. Their bodies are flattened laterally, enabling them to move easily through individual hair strands. Color ranges from translucent gray to brown, often matching the host’s hair shade, which can make them difficult to spot. The head is wider than the thorax, bearing six legs with clawed tarsi that grip each shaft securely. Live insects appear as moving specks; they may be seen crawling along the scalp or clinging to hair near the roots.
Eggs, commonly called nits, are oval, 0.8 mm long, and firmly attached to the hair shaft with a cement‑like substance. Nits are positioned 1–2 mm from the scalp, making them appear as tiny, yellow‑to‑white beads. Because they are glued in place, they do not fall off with washing. After hatching, the nymph resembles an adult but is smaller and lighter in color, maturing through three molts over approximately ten days.
Factors that lead to infestation include:
- Direct head‑to‑head contact with an infested person.
- Sharing personal items such as combs, hats, helmets, or headphones.
- Close proximity in environments where people gather, e.g., schools, camps, or daycare centers.
- Lack of regular inspection and prompt removal of nits.
- Overcrowded living conditions that facilitate transmission.
- Use of hair products that obscure visual detection, such as heavy gels or sprays.
Understanding the visual cues—mobile insects, attached eggs, and the characteristic positioning of nits—combined with awareness of transmission routes enables early identification and effective treatment.