Prevention & care
Head lice: live infestation versus nits, transmission, combing, treatment choices, and school guidance
On this page
Head lice are small insects that live on the scalp and feed on blood. Their eggs are called nits. Lice crawl; they cannot fly or jump. Infestation commonly spreads through direct hair-to-hair contact and is unrelated to whether hair is clean. Head lice do not transmit disease, although scratching can cause sores.[1]
Lice and egg cases answer different questions
| Finding | Meaning |
|---|---|
| Live louse | A crawling insect; finding one supports active infestation.[1] |
| Nit | An egg or egg case attached to hair; it may be live, dead or already empty.[1] |
| Itch | Can be delayed or absent in a light infestation; itch alone does not confirm lice.[1] |
A detection comb helps distinguish infestation from a lookalike
NHS recommends a fine-toothed detection comb to find live lice. Old egg cases can remain after treatment. An empty case and a crawling insect establish different findings; itch alone does not confirm infestation.[4]
Close contact matters more than cleanliness
CDC describes direct head contact as the main route. Lice crawl between hairs rather than jumping across a room. Pets do not carry or spread human head lice. An initial infestation may cause little recognized itching for several weeks. Stigma can delay checking without identifying how exposure happened.[1]
Physical removal and medicines work in different ways
NHS describes repeated wet combing as one option. A single quick pass is different. If unsuitable or ineffective, a pharmacist can explain local products and age restrictions; this page does not prescribe a schedule.[4]
A product that kills crawling lice may leave eggs
CDC explains that lice products differ in their effects on eggs, so follow-up and any repeat treatment depend on the particular label. More medicine or more frequent application is not automatically better. Check instructions, age suitability and other precautions; apparent failure can need review rather than improvised mixtures.[2]
Approval and a country’s preferred options are different claims
CDC’s January 2025 explanation lists FDA-approved permethrin and notes resistance with unknown prevalence. NHS does not recommend it. These differing national positions do not establish universal effectiveness or worldwide product choice.[3][4]
Persistence does not identify its own cause
Continued live lice can reflect an incorrect initial diagnosis, use inconsistent with the instructions, reinfestation or resistance. CDC discusses reviewing treatment and choosing appropriate alternatives when needed. The finding alone does not measure resistance prevalence or justify repeatedly combining medicines. Product effectiveness needs a defined population, comparison and follow-up.[3][2]
Contact checks and environmental advice have a limited purpose
CDC advises checking household and close contacts and coordinating treatment for affected people. Contact checks address repeat exposure; they do not establish that every household member has lice.[2]
CDC includes targeted laundering; NHS says hot washing is unnecessary. Local guidance should remain visible rather than requiring universal household sterilization.[2][4]
Distress can be greater than the physical harm
The inspected 2022 American Academy of Pediatrics report abstract describes limited morbidity but substantial caregiver anxiety. It is a professional clinical report, not a new treatment trial. Only the original indexed abstract was inspected; unseen report details cannot establish a product ranking or a school policy here.[5]
School policy and active treatment are separate questions
NHS says children with head lice need not stay off school. Local policies can differ. An old nit is not proof of active infestation.[4]
Evidence & uncertainty
Treatment depends on live-lice detection, age and product instructions. Guidance differs by country; approval does not guarantee effectiveness. Persistence can have several causes.[4][3]
Selected-source overview · Independent review pendingPublished questions
Are nits the same thing as crawling head lice?
Selected-source overview · Independent review pending. Read the evidence context.
Nits are eggs or egg cases; lice are the insects.[1]
Evidence behind this answer
- About Head Lice
agency condition or prevention explanation · 2024
Selected relevant original official page passages inspected · Insect and nit biology, delayed itch, crawling and stigma
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Do empty nit cases prove an active head-lice infestation?
Selected-source overview · Independent review pending. Read the evidence context.
Finding a live louse is different from finding an old egg case.[4]
Evidence behind this answer
- Head lice and nits
agency condition or prevention explanation · Date not stated
Selected relevant original official page passages inspected · Live-lice detection, combing, school and different product guidance
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Does getting head lice mean someone has dirty hair?
Selected-source overview · Independent review pending. Read the evidence context.
Infestation is unrelated to hair cleanliness.[1]
Evidence behind this answer
- About Head Lice
agency condition or prevention explanation · 2024
Selected relevant original official page passages inspected · Insect and nit biology, delayed itch, crawling and stigma
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Can head lice jump or fly between people?
Selected-source overview · Independent review pending. Read the evidence context.
They crawl and mainly spread through close hair contact.[1]
Evidence behind this answer
- About Head Lice
agency condition or prevention explanation · 2024
Selected relevant original official page passages inspected · Insect and nit biology, delayed itch, crawling and stigma
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Does every head-lice product kill unhatched eggs?
Selected-source overview · Independent review pending. Read the evidence context.
Egg activity and label-directed follow-up differ by product.[2]
Evidence behind this answer
- Treatment of Head Lice
agency condition or prevention explanation · 2024
Selected relevant original official page passages inspected · Product egg activity, contacts, application limits and housekeeping
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Do CDC and NHS give identical advice about permethrin for head lice?
Selected-source overview · Independent review pending. Read the evidence context.
CDC lists an approved option; NHS does not recommend it.[3]
Evidence behind this answer
- Clinical Care of Head Lice
agency condition or prevention explanation · 2025
Selected relevant original official page passages inspected · Approved products, resistance uncertainty and reviewing persistence
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Does persistent head lice automatically prove drug resistance?
Selected-source overview · Independent review pending. Read the evidence context.
Diagnosis, product use and reinfestation also need assessment.[3]
Evidence behind this answer
- Clinical Care of Head Lice
agency condition or prevention explanation · 2025
Selected relevant original official page passages inspected · Approved products, resistance uncertainty and reviewing persistence
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Does the NHS require children with head lice to stay off school?
Selected-source overview · Independent review pending. Read the evidence context.
Its patient guidance says school absence is unnecessary.[4]
Evidence behind this answer
- Head lice and nits
agency condition or prevention explanation · Date not stated
Selected relevant original official page passages inspected · Live-lice detection, combing, school and different product guidance
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
Does the difficult-to-treat trial establish oral treatment for every child with lice?
Selected-source overview · Independent review pending. Read the evidence context.
Its eligibility and prior-treatment requirements limit that inference.[6]
Evidence behind this answer
- Oral ivermectin versus malathion lotion for difficult-to-treat head lice
randomized trial · 2010
Selected relevant original page/abstract passages inspected; no independent full-text appraisal · Previously failed topical therapy, age/weight eligibility and day-fifteen endpoint
This answer summarizes selected sources. An independent appraisal of the complete evidence has not been completed.
A difficult-to-treat trial is not first-line evidence for every child
A randomized trial favored oral ivermectin over malathion lotion for live lice persisting after topical treatment. Participants were at least two years old and weighed at least fifteen kilograms; treatment occurred at study sites. That selected refractory population and endpoint cannot establish routine oral treatment for every infestation or safety for younger or smaller children. Local clinical guidance determines suitability.[6]
References
- About Head Lice
Agency condition or prevention explanation
CDC · Content/publication date: 2024
Accessed: 2026-10-08 UTC · Selected relevant original official page passages inspected
Cited sections: Insect and nit biology, delayed itch, crawling and stigmaDated 4 June 2024; head lice do not transmit disease.
- Treatment of Head Lice
Agency condition or prevention explanation
CDC · Content/publication date: 2024
Accessed: 2026-10-08 UTC · Selected relevant original official page passages inspected
Cited sections: Product egg activity, contacts, application limits and housekeepingDated 12 November 2024; no individual product or dosing plan.
- Clinical Care of Head Lice
Agency condition or prevention explanation
CDC · Content/publication date: 2025
Accessed: 2026-10-08 UTC · Selected relevant original official page passages inspected
Cited sections: Approved products, resistance uncertainty and reviewing persistenceDated 31 January 2025; approval does not establish universal effectiveness.
- Head lice and nits
Agency condition or prevention explanation
NHS · Content/publication date: not stated
Accessed: 2026-10-08 UTC · Selected relevant original official page passages inspected
Cited sections: Live-lice detection, combing, school and different product guidanceUK advice differs from CDC on permethrin and hot laundering.
- Head Lice
Professional clinical report
Nolt D and colleagues; American Academy of Pediatrics · Content/publication date: 2022
Accessed: 2026-10-08 UTC · Selected original indexed clinical-report abstract inspected; no independent full-text appraisal
Cited sections: Limited morbidity, caregiver anxiety and report scopeProfessional report, not a new trial or universal product ranking.
- Oral ivermectin versus malathion lotion for difficult-to-treat head lice
Randomized trial
Chosidow O and colleagues · Content/publication date: 2010
Accessed: 2026-10-13 UTC · Selected relevant original page/abstract passages inspected; no independent full-text appraisal
Cited sections: Previously failed topical therapy, age/weight eligibility and day-fifteen endpointSelected-source explanation. Citation matching does not establish an independent evidence appraisal.
Scope & review
- Population
- General family and school infestation literacy; age-specific product restrictions remain separate
- Exposure or intervention
- Detection combing, contact checks and locally recommended lice products
- Comparison
- Source-specific test methods, placebo/usual care, or prevention settings
- Outcomes
- Active infestation, egg cases, persistence, reinfestation and caregiver burden
- Timeframe
- Initial detection, product-specific follow-up and continuing exposure
- Jurisdiction
- WHO global frameworks with selected US/UK explanations; eligibility and programs vary locally
Selected-source educational explanation. Official guidance, original study findings and editorial interpretation are distinguished. No exhaustive search, independent systematic synthesis or qualified medical review has been completed.
Sources checked on their individual access dates. Selected sources were checked; ongoing surveillance and qualified review have separate statuses on the coverage page.
Revision history
- 2026-10-08 UTC: Added a sourced explanation in a bounded ten-article batch; qualified review remains pending.
- 2026-10-13 UTC: Deepened categories, applicability, uncertainty and competing interpretations using additional verified sources; prior anchors retained.
What this article still leaves open
- A full product-comparison, resistance and school-policy review and independent clinical review remain incomplete.
- No individual infestation diagnosis, product choice or application calendar is supplied.
Suggest a correction
Submit a content correction to the editorial queue, or download a local note. Leave out personal medical details. Submitted text is stored privately with a browser receipt session and is visible to this browser and the editor. Clearing cookies removes access to your submission history. This is not an account or a medical service.
Your submitted corrections for this article
Explore the topic map
Browse the health domains connected to this article. The map also identifies topics whose articles remain unwritten.