Entity scope
This profile covers head lice, Pediculus humanus capitis, on human scalp hair. It does not cover body lice or pubic lice, which have different contexts and health implications.
Quick identity
- Scientific name
- Pediculus humanus capitis
- Host
- Humans; pets do not carry or spread human head lice
- Movement
- Crawls; does not jump or fly
- Strong evidence
- A live louse on scalp hair or a viable egg firmly attached near the scalp
- Disease boundary
- Head lice are not the body-lice form associated with disease transmission
- Visual status
- NO_VISUAL — direct careful examination is more useful
Key characteristics
- Adults are small flattened insects with six legs adapted to grasp hair.
- Eggs are firmly attached to hair shafts; loose flakes and debris have many alternatives.
- Head lice crawl and usually spread through direct head-to-head contact.
- The head-louse and body-louse contexts must not be combined into one disease claim.
Life stages
01
Egg / nit
Attached to a hair shaft; distance from the scalp and viability matter.
02
Nymph
Smaller mobile stage that resembles the adult.
03
Adult
Six-legged crawling insect living close to the scalp.
Where it is found
- Scalp hair, especially behind the ears and near the neckline during careful examination.
- Head-to-head contact is the primary transmission context; indirect spread is less common.
Behavior and activity
- Head lice remain on humans and feed on blood at the scalp.
- They crawl rather than jump or fly.
- Itching or a suspected nit alone does not prove active infestation.
Associated signs
Finding a live crawling louse is the strongest practical evidence; hair-attached objects require careful differentiation from dandruff and debris.
Common lookalikes
Usually loose or easily moved rather than firmly attached like a nit.
A different human-louse form associated mainly with clothing seams and different public-health context.
Jumping insects associated with animal/environmental cycles rather than scalp hair.
Why it matters
Active infestation requires direct evidence
Head lice can cause itching and scratching-related irritation, but they are not known to transmit disease. This must not be confused with body-lice disease risk.
- Get medical advice for infection concerns, severe scalp inflammation, uncertain diagnosis, or treatment questions.
- Do not treat someone solely because of itching or exposure without checking for active infestation.
- Follow age, product, and repeat-use directions exactly; this Profile does not prescribe medication.
Management direction
- Confirm live lice through careful scalp and hair examination.
- Check close contacts according to current public-health guidance without stigmatizing the person or household.
- Use CDC or healthcare guidance for treatment; do not use pesticides intended for rooms, pets, or other pests on people.
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Identify a photoReviewed guidance and sources
Last reviewed August 2026. Sources support the claims listed with them; their limits remain part of the review.
- CDC — Lice
Supports: Separation of head, body, and pubic lice and the human-host context.
Does not support: A diagnosis from itching or a suspected nit.
Scope note: Guidance and risk vary by geography, exposure, and individual health context.
- CDC — Hair and Scalp Hygiene: Head Lice
Supports: Primary head-to-head spread and limited indirect transmission context.
Does not support: Proof of active infestation without a louse or viable egg.
Scope note: Guidance and risk vary by geography, exposure, and individual health context.