Head lice (pediculosis capitis)
Pediculus humanus capitis infestation of the scalp hair
Overview
Infestation of the scalp hair by the head louse, spread by head-to-head contact, common in school-age children. Live lice confirm active infestation; nits (egg cases) alone may be old. Itch is from sensitisation and may be absent early.
Recognise
- Itch of the scalp (especially behind the ears and nape), though often asymptomatic
- Live lice and viable eggs (nits) cemented to hair shafts close to the scalp
- Spreads by direct head-to-head contact; common in school outbreaks
Red flags
- Secondary bacterial infection of excoriated scalp
Differentials & how to tell them apart
Clinical image
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Investigations
Detection (wet) combing of the hair confirms LIVE lice — diagnosis requires a living louse, not just nits.
Management
Dimeticone 4% lotion (two applications 7 days apart) or systematic wet combing
- 1Treat only if LIVE lice are found. Dimeticone 4% lotion with a repeat application after 7 days (to kill lice hatching from surviving eggs), or wet combing.Gate: Treat only confirmed ACTIVE infestation (a living louse) — nits (empty egg cases) alone do not warrant treatment; and always repeat after 7 days because no product is fully ovicidal
- 2Check and treat affected household contacts; no need to exclude from school. Resistant cases → switch agent class.
Key points
No need to keep children off school. Conditioner-and-comb detection is the diagnostic test. Repeat treatment at day 7 because eggs survive the first application.
Monitor & prognosis
Re-check by combing after treatment; re-treat contacts.
Cured with correct repeated treatment.
Source: NICE CKS Head lice; DermNet