Head Lice
Head lice are small insects that live on the scalp and glue their eggs to the hair. They spread through head-to-head contact, they do not carry disease, and they have nothing to do with how clean anyone is. Treatment clears them, but it almost always has to be repeated.
Key facts
Head Lice at a glance.
Typical signs
Lice or eggs attached to hair
Common locations
Scalp, behind ears, nape
Expected course
Clears with treatment
Treatment options
Lice treatment and combing
What is it?
Top things to know about Head Lice
- Lice live on the scalp. They feed on the scalp and attach eggs to hair shafts.
- Itching can come late. It is a reaction to bites and may not start straight away.
- Inspection comes first. A fine-toothed comb in good light confirms lice before treatment.
- Empty cases are not failure. Hatched egg cases stay attached as hair grows.
What it looks like
What Head Lice looks like
Head lice are tiny wingless insects, about the size of a sesame seed, that live on the scalp and feed on small amounts of blood. Adult lice move quickly and avoid light, so they are often hard to spot. Their eggs, called nits, are easier to find. Nits are glued firmly to the hair shaft close to the scalp and don't brush or flick off like dandruff. Itching, caused by a reaction to louse saliva, can take weeks to start after a first infestation.
Adult lice
Tan to gray insects about 2–3 mm long.
Nits on the hair
Oval eggs glued close to the scalp.
Scratch marks
Red bumps behind the ears and on the neck.
Where it shows up
Check scalp hair, particularly behind the ears and at the nape. The shading shows inspection areas, not a rash.
Scalp and behind the ears
Locations on the back of the head.
Neck
Locations around the neck and nape.
On different skin tones
Head Lice on different skin tones
Head lice look the same on every skin tone, but the signs of scratching differ. On lighter skin, bites and scratch marks look pink or red. On brown and Black skin, they may look darker brown or purple and can leave dark marks after healing. Nits can be harder to see against light-colored hair and easier against dark hair, which matters more than skin tone when checking.
What happens in Head Lice?
Head lice live among scalp hairs, feed on blood and attach their eggs to hair shafts. The body's reaction to their saliva causes itching, which may take time to develop after a first infestation.
- Lice move between hairs: Close head contact commonly spreads them.
- Eggs cling to hair shafts: Nits are cemented near the scalp.
- Bites can cause itching: The skin reacts to louse saliva.
Causes and triggers
What causes Head Lice
Causes
Why it happens
Head lice are tiny insects that live only on the human scalp. They can't jump or fly, so they spread by crawling from one head to another.
Risk factors
Raise the odds
- Ages 3 to 11
- Long hair
- Close-contact play
- Shared household
Triggers
Passes it on
- Head-to-head contact (Well established)
- Sleepovers and shared beds (Strong link)
- Shared hats, combs and brushes (Possible)
When it usually starts
When it usually starts
Head Lice
Most common in school-age children; close contacts of any age can be affected.
Daily care
Daily care for Head Lice
Check every household member
Check household members for live lice on the same day.
Tell the school and close families
The most effective way to stop the cycle.
Wash recent bedding and hair items
Hot water and high heat, last two days.
Skip the deep clean of the house
Lice die within a day or two off a scalp.
Keep long hair tied back
A small measure, and an easy one.
An over-the-counter treatment
Permethrin or pyrethrin, exactly as the leaflet says.
Treat the itch while it settles
A gentle shampoo, antihistamine at night if needed.
Check again after the second treatment
Look for live moving lice, not nits.
Apply lice medicine to wet or dry hair exactly as that product instructs
Different lice products have different instructions. Follow the stated hair preparation, amount, contact time and repeat schedule.
Ask about another lice treatment if live lice persist after correct use
Persistent live lice can reflect resistance, incorrect use or reinfestation; ask a clinician or pharmacist before repeating courses.
Avoid: Not checking everyone at home
One untreated head reseeds the rest.
Avoid: Scratching
Breaks the skin at the nape, lets infection in, leaves lasting marks.
Avoid: Sharing hats, brushes and combs
Headbands and headphones too.
Avoid: Hiding it
A group of children can pass it around for a term.
Avoid: Kerosene, gasoline or bleach
Dangerous — burns, poisoning and fires have resulted.
Avoid: Skipping the second treatment
Most products do not kill eggs.
Avoid: Conditioner just before treatment
It coats the hair and blunts some products.
Avoid: Treating on nits alone
Empty shells stay glued on for months.
Avoid: Washing the hair too soon after
Some treatments keep working a day or two.
Avoid: Lindane
An old prescription shampoo that is no longer recommended for head lice. It is less effective than the current options and has caused seizures when overused or used on broken skin. It is included here only because people still come across it — there is no situation now where it is the right choice.
Treatments
Treatments for Head Lice
Permethrin
The usual first treatment, applied to dry hair, left the stated time and rinsed, then repeated in seven to ten days because it does not reliably kill eggs. Where lice are not resistant it works well. Resistance to it is now common in many areas, so if two proper courses fail, the answer is a different medicine, not a third round.
Pyrethrin shampoo
The other older over-the-counter option, from chrysanthemum extract, used the same way with a repeat in seven to ten days. It kills fewer eggs than permethrin does and lice are commonly resistant to it. It is avoided in anyone with a ragweed or chrysanthemum allergy.
Dimethicone
A silicone lotion that coats and suffocates the lice rather than poisoning them, so resistance is not an issue with it. It is left on for the stated time — often several hours or overnight — and repeated a week later. It is a good option for a child who has already failed permethrin, and it is gentle on the scalp.
Tea Tree Oil
Sold in several natural lice products and not shown to clear an infestation reliably. It irritates the scalp of a child who is already scratching, and it is a common cause of allergic reactions. If the older products have stopped working, a prescription treatment is a better answer than an essential oil.
Ivermectin Lotion
Ivermectin lotion 0.5%. A single ten-minute application to dry hair, and usually no repeat is needed, because it kills the young lice as they hatch. That makes it a good choice for families who have already skipped or fumbled a second application. It is one of the main options when permethrin has failed.
Spinosad
Spinosad suspension. A ten-minute application to dry hair that kills both lice and most eggs, so a second treatment is often unnecessary. High cure rates in studies against permethrin-resistant lice. Cost and availability are the usual limits rather than how well it works.
Malathion
Malathion lotion. An older prescription lotion that kills lice and many eggs, applied to dry hair and left on for the stated time. It works where permethrin has failed. It smells strongly, it is flammable while wet so no hairdryers, flames or cigarettes near it, and it is not used in young children.
Benzyl Alcohol Lotion
Benzyl alcohol lotion. It works by blocking the breathing holes of the lice rather than poisoning them, so resistance is not expected. It does not kill eggs, so the repeat in seven days is essential. It can sting and irritate the scalp, which matters if the skin is already scratched.
Oral Ivermectin
Ivermectin tablets. A tablet taken as two doses about a week apart, used when repeated topical treatments have failed or when applying a lotion to the whole scalp is not practical. It is effective in that situation. It is not used in small children or in pregnancy, so the prescriber checks weight and circumstances first.
Outlook
What to expect with Head Lice
Left alone, head lice do not clear. They cause no lasting damage; the problems come from scratching, and occasionally infection on top.
- 1
Arrival · Day 0
A louse or two crawl across during head contact.
- 2
Eggs and hatching · Days 1 to 10
The female glues eggs to hair shafts near the scalp within a day or two. The first hatch around day 7 to 10. Empty shells stay glued on and grow out.
- 3
Building up · Weeks 2 to 3
The new lice mature and lay their own eggs.
- 4
The itch · Weeks 4 to 6
In a first infestation the allergic reaction to louse saliva finally develops. Someone who has had lice before itches within days.
- 5
Treatment · Day 1, then day 8 to 10
The first kills live lice; eggs often survive. The second catches the generation that hatched after it. Itching can carry on one to two weeks after the last louse, because the allergy takes time to fade. Months of failed treatment is more often a social and emotional problem than a medical one.
Complications
Complications to know about
Infected scalp and neck
Scratching breaks the skin, and bacteria can get in on top. The signs are redness and swelling that spreads, weeping or honey-colored crusts at the nape and behind the ears, and tender glands in the neck. It is the main reason a case of lice ever needs antibiotics, and it needs to be seen. Treating the lice properly and settling the itch early is what prevents it.
Weeks of broken sleep and worry
The lasting harm from head lice is rarely medical. It is the itching that keeps a child awake, weeks of repeat treatments and combing, missed school where old exclusion policies are still used, and the embarrassment that makes families treat it in secret. Telling the school and the other families is the single most effective thing for ending the cycle, and it is the step people most want to skip.
When to get help
When to get help
When to seek care
Ask a pharmacist or clinician if you cannot confirm live lice, treatment fails, or scratching causes sores or infection.
Lookalikes
What else could it be?
Dandruff
Dandruff flakes brush away easily. Lice eggs are attached firmly to individual hairs and usually cannot be flicked or brushed off.
Seborrheic Dermatitis
Seborrheic dermatitis leaves greasy scale on irritated scalp patches. Head lice leave eggs attached to hairs, and a live louse may be found with a comb.
Scalp Psoriasis
Scalp psoriasis forms thick, clearly edged patches, sometimes beyond the hairline. Lice leave eggs stuck to hairs rather than raised patches of skin.
Questions
Questions you might be asking.
How did my child get them?
Almost certainly direct head-to-head contact with another child — playing on the floor, a sleepover, photographs head to head. Not the house, the pets or anyone's hair. By the time you find them the contact was weeks ago.
Does my child have to stay home from school?
Major pediatric and public health bodies advise against sending children home for lice. By the time they are found they have usually been there for weeks, and lice do not spread easily in a classroom. Tell the school, start treatment, and in most places the child stays. Check your school's policy — some are stricter than the guidance.
Do I have to get every nit out?
No. It makes future checks easier and reassures everyone, but empty shells are harmless and grow out. What matters is that no live lice remain. Combing with conditioner and a metal comb beats picking them out dry.
Why is my child still itching after treatment?
Because the itch is an allergic reaction, not the lice, and takes one to two weeks to settle after the last louse is gone. The scalp has also been scratched and treated with something drying. Itching alone is not a reason to treat again. Finding a live louse is.
Do I need to treat everyone in the family?
Check everyone the same day and treat the ones with live lice. Some doctors also treat anyone who shares a bed, even with no live lice found, because that contact is so close. Treating the whole household regardless is not recommended.
Why did the treatment not work?
In order of likelihood: the second application was skipped, the product was misused, someone else in the house was not treated, reinfection came from the same friend or classroom, or the lice are resistant. Only the last is a reason to change medicine, so work through the other four first.
Sources
Sources and further reading
Related
Keep exploring.
Dandruff
Tea Tree Oil
Permethrin
Scalp Psoriasis
Seborrheic Dermatitis
Dimethicone
Dandruff vs Head Lice
Scabies vs Head Lice
Head Lice vs Scalp Folliculitis
Psoriasis
Pyrithione Zinc