How long after lice does symptom appear? - briefly
It typically takes 4–6 days after a lice infestation for itching and irritation to develop, when the insects begin feeding and their saliva provokes a reaction. Onset can vary slightly based on individual sensitivity.
How long after lice does symptom appear? - in detail
The itching and irritation caused by a lice infestation usually begin several days after the insects have started feeding. The timeline differs slightly between head lice and body lice, but the general pattern is consistent.
- Eggs (nits) hatch in about 7‑10 days. Newly emerged nymphs require a blood meal to mature.
- Initial feeding triggers a mild, localized itching that can appear as early as 3‑5 days after the first bite.
- Full‑size lice develop within another 5‑7 days. By this stage, the host typically experiences more pronounced pruritus, redness, and possible skin lesions from scratching.
- Secondary bacterial infection may develop if the skin is broken, usually 10‑14 days after the infestation becomes established.
Factors influencing the onset of symptoms include:
- Individual sensitivity to lice saliva; some people react sooner.
- Density of the lice population; larger numbers increase irritation faster.
- Location of infestation; body lice, which live in clothing, often produce symptoms later than head lice because they feed less frequently.
In summary, noticeable discomfort generally starts within a week of the first feeding, intensifies over the next several days as the lice mature, and can lead to complications if left untreated for two weeks or more. Prompt identification and treatment interrupt this progression and prevent further skin irritation.