Head lice (pediculosis capitis) are tiny wingless insects that live on the scalp and feed on blood. They spread mainly by direct head-to-head contact, are most common in school-age children and are a nuisance, not a sign of poor hygiene or a carrier of disease.
Key symptoms
- Itchy scalp, often behind the ears and at the back of the neck
- Feeling of something moving in the hair
- Scratch marks or sores on the scalp
- Many children have no symptoms
What you find on exam
- Live lice seen on the scalp or caught with a fine-tooth comb in wet hair
- Nits (eggs) firmly attached to hair shafts within 1 cm of the scalp
- Nits do not brush off easily, unlike dandruff
- Swollen neck lymph nodes or crusting from secondary infection
Tests
- Diagnosis by finding a live louse; wet combing is the most reliable method
- Nits alone far from the scalp do not prove an active infestation
- Bacterial culture only if scalp sores look infected
Treatment basics
- Over-the-counter permethrin 1 percent lotion, repeated in 9 to 10 days
- Prescription options if resistance is likely: topical ivermectin, spinosad or malathion
- Wet combing with a fine-tooth comb every few days for 2 weeks
- Check household contacts and treat only those with lice; wash bedding and hats in hot water
- No need to keep children home from school
Red flags
- Treatment failure despite correct use (check technique and resistance)
- Infected scalp sores, crusting or fever
- Lice on the eyelashes or in the pubic area (consider other causes, including abuse in children)
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Related guides
Sources: NCCPA PANCE Content Blueprint; NBOME COMLEX-USA clinical presentations; AAMC Core Entrustable Professional Activities (Core EPAs). Written by Making Synapses. Making Synapses is not affiliated with these organizations.