How to Check for Head Lice
Detection combing done properly, how to tell a live louse from a nit from dandruff, and why looking through the hair by eye misses so much.
Part of the Complete Head Lice Guide.
Key fact: Detection combing is over three times more effective than looking through the hair by eye, and more than twice as fast. Parting the hair and peering at the scalp is the method almost everyone uses, and it is the one that misses infestations.
Why combing beats looking
Lice move fast, avoid light, and there are often very few of them — an early infestation may be a single louse on a whole head. Visual inspection finds these poorly. Combing physically drags them out of the hair whether or not you happen to look in the right place.
It also answers the question that matters: is there a live louse. Nothing else does, and without that answer you are guessing about whether to treat at all.
What you need
- A proper detection comb — teeth spaced 0.2 to 0.3mm apart. Ordinary plastic nit combs are often too coarse and let lice through
- Ordinary hair conditioner, generously applied
- White kitchen roll or a white tissue to wipe the comb on
- Good light, ideally daylight or a bright bathroom
- Patience — 10 minutes for short hair, 20 to 30 for long, frizzy or curly hair
The method
| Step | What it involves |
|---|---|
| Wash and condition | Wash the hair, then apply plenty of conditioner and leave it in. The conditioner immobilises lice and lets the comb move |
| Detangle first | With an ordinary wide-toothed comb, so the fine comb can move without pulling |
| Comb from the scalp outwards | Start with the comb touching the scalp, near the crown, and draw it firmly to the ends of the hair |
| Check the comb every stroke | Wipe it on white kitchen roll and look before the next stroke |
| Work around the whole head | Section by section, so every part is combed at least twice |
| Rinse the conditioner out | Once you have finished |
Combing dry hair also works and is quicker, but wet combing with conditioner is more reliable, because lice are held still rather than scattering.
Telling what you have found
| What it is | How to recognise it | Does it mean treat? |
|---|---|---|
| A live louse | Black, brown or grey-white, sesame-seed sized, moving — it clings to the comb and to hair | Yes |
| A viable egg | Small, brown, firmly glued to a hair close to the scalp | Recheck carefully — there are almost certainly lice too |
| A nit | White or clear empty shell, still glued to the hair, often well away from the scalp | No — evidence of a past infestation |
| Dandruff or product residue | Flakes that lift off easily and move when blown | No |
| Hair casts | White cylinders that slide freely along the hair | No — nits do not slide |
The slide test. Try to move what you have found along the hair with your fingers. Nits and eggs are cemented and will not budge; dandruff, casts and product residue slide off easily. It takes two seconds and settles most arguments.
Where they hide
- Behind the ears
- At the nape of the neck
- On the crown
- Along the hairline at the temples
These are the warmest parts of the scalp and where eggs are most often laid, but a proper comb-through covers the whole head regardless — lice do not stay in one place while you look for them.
How often to check
- Once a week is a reasonable routine for a primary-school-aged child, folded into a hair-washing night
- Whenever a letter comes home from school, or a close contact has them
- Whenever there is unexplained scalp itching, remembering the itch can lag weeks behind
- Everyone in the household on the same evening, when lice are found on one person
Routine checking does not prevent head lice — nothing does — but it catches them when there are fewer, which means less treatment and less passed on.
Checking after treatment
- Comb 2 to 3 days after the final application to confirm no live lice remain
- Comb again about a week later, which catches anything hatched since
- Finding nits only is not failure — empty cases stay glued for months and do not need treating
- Finding live lice after a full, correctly used course means something has gone wrong — see treatments compared
- Continuing itch is not failure either, and can last weeks after successful treatment
Things that are not head lice
- Dandruff and seborrhoeic dermatitis — flaking that lifts off, often with a greasy yellow scale at the hairline
- Scalp psoriasis — thicker, well-defined silvery plaques
- Hair product residue — dry shampoo and styling products leave white deposits
- Hair casts — white cylinders that slide along the hair
- Scalp ringworm — scaly patches with hair loss and broken hairs, which needs antifungal treatment
- Delusional parasitosis — a persistent conviction of infestation without lice ever being found, which deserves a kind conversation rather than more insecticide
Frequently Asked Questions
What is the best way to check for head lice?
Detection combing with a fine-toothed comb through wet, conditioned hair. It is more than twice as fast as visual inspection and over three times more effective. Comb from the scalp outwards, check the comb on white kitchen roll after every stroke, and cover the whole head at least twice.
How can I tell a nit from dandruff?
Try to slide it along the hair. Nits and eggs are cemented to the hair shaft and will not move; dandruff, hair casts and product residue slide off easily or lift away. Nits are also usually white or clear empty shells, often some distance from the scalp.
Does finding nits mean my child has head lice?
Not necessarily. Nits are empty egg cases left after hatching, and they stay glued to the hair for months as it grows out. They show that there was an infestation at some point. Only finding a live louse justifies treatment.
How often should I check my child's hair?
About once a week for a primary-school-aged child is a reasonable routine, and whenever a letter comes home or a close contact has them. Checking does not prevent head lice, but it finds them earlier, when there are fewer and less has been passed on.
My child still itches after treatment. Do they still have lice?
Not necessarily. The itch is an allergic reaction to louse saliva and can persist for weeks after the lice have gone, just as it can take weeks to develop in the first place. Comb to check rather than treating again on the strength of itching.
References
- NHS. Head lice and nits. nhs.uk
- National Institute for Health and Care Excellence. Clinical Knowledge Summary: Head lice. cks.nice.org.uk
- Welsh Medicines Information Centre. Head Lice: Questions and Answers for Healthcare Professionals. wmic.wales.nhs.uk
- UK Health Security Agency. Health protection in children and young people settings, including education. gov.uk
- Burgess IF et al. Randomised, controlled, assessor blind trial comparing 4% dimeticone lotion with 0.5% malathion liquid for head louse infestation. PLoS ONE 2007. journals.plos.org
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Head lice treatment should only be used when a live louse has actually been found, and product instructions vary, so always read the leaflet supplied. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.