When does itching start from lice? - briefly
Itching usually begins 24–48 hours after the insects start feeding on the scalp, as saliva from the «lice» triggers an allergic skin response. In some cases, symptoms may be delayed up to a week.
When does itching start from lice? - in detail
Lice infestations trigger an allergic reaction to saliva and feces deposited on the scalp. The immune response usually becomes noticeable within a few days after the insects begin feeding.
Typical onset periods:
- 24–48 hours: mild irritation may appear, often mistaken for a dry scalp.
- 48–72 hours: localized redness and a faint tingling sensation develop as histamine release intensifies.
- 3–5 days: pronounced itching emerges, accompanied by small red papules or bumps.
- 5–7 days: itching reaches its peak intensity; scratching can cause secondary inflammation or infection.
Factors influencing timing:
- Individual sensitivity: people with heightened allergic responses experience itching sooner.
- Infestation size: larger numbers of lice increase saliva exposure, accelerating symptom development.
- Age: children’s skin is more reactive, leading to earlier discomfort.
- Hygiene and scalp condition: oily or dirty scalps may retain more irritants, shortening the latency period.
Physiological mechanism:
- Lice bite the scalp and inject saliva containing anticoagulants.
- Saliva proteins act as allergens, prompting the body’s immune system to release histamine.
- Histamine dilates blood vessels, causing redness, swelling, and the characteristic itch.
- Repeated bites amplify the response, resulting in progressive symptom escalation.
Recognition of the early stage is crucial for prompt treatment, as timely removal of lice can halt the allergic cascade and prevent severe itching.