What symptoms do lice cause and why do they appear? - briefly
Lice infestations produce intense itching, scalp redness, and occasional secondary skin infections caused by their bites. They arise when adult females deposit eggs on hair shafts and spread through direct head-to-head contact.
What symptoms do lice cause and why do they appear? - in detail
Lice infestations produce several recognizable signs. The most common manifestation is intense itching, especially around the scalp, neck, and ears. Itching results from the bite of the insect and the host’s allergic reaction to saliva proteins. Additional symptoms include:
- Small, pale‑white nits attached firmly to hair shafts, usually within a quarter‑inch of the scalp.
- Live insects, about the size of a sesame seed, that move quickly when the hair is examined.
- Red or inflamed spots where bites have occurred, sometimes accompanied by secondary bacterial infection if scratching breaks the skin.
- A feeling of “movement” or “crawling” on the scalp, reported especially by children.
These effects arise because lice feed exclusively on human blood. Their mouthparts pierce the epidermis, delivering saliva that contains anticoagulants and irritants. The host’s immune system responds with histamine release, producing the characteristic pruritus. Repeated feeding leads to cumulative skin irritation and, in severe cases, crusted lesions.
The presence of nits is a direct consequence of the lice reproductive cycle. Female lice lay 6‑10 eggs per day, cementing them to the hair shaft with a proteinaceous glue. Eggs hatch in about seven days, releasing nymphs that mature within another week. The rapid turnover of the population sustains the infestation and perpetuates the symptoms.
Environmental factors contribute to the emergence of lice. Close head‑to‑head contact, shared combs, hats, or bedding facilitate transmission. Overcrowded settings and inadequate hygiene increase the risk of initial colonization. Once a few insects establish themselves, the cycle of feeding, egg‑laying, and hatching quickly amplifies the visible and sensory signs.