Head Lice: How to Tell for Sure, and What Actually Gets Rid of Them

What do head lice look like?

An adult head louse is a flat, wingless, tan or greyish insect about 2 to 3 mm long, roughly the size of a sesame seed. It has six legs, each ending in a claw that grips one hair. Young lice, called nymphs, are smaller and paler. The eggs, called nits, are tiny ovals glued to the hair near the scalp.

The scientific name is Pediculus humanus capitis, and an infestation is called pediculosis capitis. Head lice live only on people. They spend their whole life in the hair on the head, and they cannot survive more than a day or two away from it, according to both the CDC and UC IPM.

People often ask what lice look like to the human eye. Honestly, at a glance most parents see a quick brown speck that vanishes into the hair. Under a magnifier or a phone camera zoomed in, you can see the six legs. If the speck does not move and is stuck to a hair, it is more likely a nit.

Sizes from the CDC and UC IPM. Nit position from Mayo Clinic. Egg colour from UC IPM.

What do lice eggs (nits) look like?

A nit is an oval egg about 0.8 mm long, glued to a single hair. UC IPM says developing eggs are darker, and they turn white after hatching. A female louse cements each egg within about 1/8 inch (3 mm) of the scalp, so fresh nits sit close to the skin.

Size is where a lot of advice goes wrong. Some guides say nits are as big as a sesame seed, which is the size of the adult. Others give figures far too small to see. UC IPM, a peer-reviewed University of California program, measures a nit at 1/32 inch, or 0.8 mm. That is small but easy to see against a single hair under good light.

The glue is the giveaway. A nit is cemented to the hair shaft, and it does not slide or flick off. You have to pull it off with a fingernail or a nit comb. Nits also blend in. UC IPM notes they are camouflaged in light-coloured hair, and Mayo Clinic says empty nits are easiest to see on darker hair.

Live nit or dead nit?

Distance from the scalp tells you more than colour does. An egg is laid right at the scalp, then moves outward as the hair grows. The CDC says nits more than 1/4 inch (6 mm) from the base of the hair are almost always hatched or dead. Mayo Clinic gives a similar threshold of 1/4 to 3/8 inch (6 to 9.5 mm).

Nits but no live lice?

This is one of the most common questions after a treatment, and the answer is usually good news. The nits you keep finding are empty shells that have grown out with the hair. Shells stay glued for weeks after the lice are gone. Johns Hopkins Medicine says that if you see no live, crawling lice three weeks after treatment, it is safe to assume they are gone.

Before treatment, though, nits with no lice need a closer look. Search again in two days with a wet comb. If nits sit within a quarter inch of the scalp, keep checking every couple of days, since live lice are fast and easy to miss.

Lice or dandruff? Things that look like nits

The quickest test takes five seconds: try to flick the speck off. Dandruff, dry skin and hair product residue brush, blow or wash away. A nit stays glued to the hair and has to be pulled off. Mayo Clinic lists five things that can be mistaken for nits. Most flick or wash away. Hair casts and fungal changes sit on the hair shaft, so if a speck will not move and you are not sure, ask a doctor.

Mistakes here are common, even among professionals. UC IPM describes a Harvard study of 600 samples sent in as lice or nits by teachers, parents, nurses and doctors. Fewer than two thirds actually contained lice or nits, and only half of those were alive. So it pays to look twice before you treat.

Look-alikes from Mayo Clinic and the CDC. The flick test from UC IPM and Harvard Health.

Small bugs land in hair too. Pale booklice, about 1 to 2 mm, sometimes turn up on a pillow or a book and get called lice, but they live on mould in damp rooms and never on people. Our guide to tiny white bugs around the house covers them. For dark specks that turn out to be beetles or other insects, see small black bugs. And if you have a clear photo of the thing you found, the bug identifier by picture can tell you what it is.

Early signs of head lice

The first sign is usually itching on the back of the head, the neck or behind the ears. The CDC says the itch can take 4 to 6 weeks to start the first time someone gets head lice, because it is an allergic reaction to the bites. Some people never itch at all.

That delay explains a lot. By the time a child scratches, or a school letter arrives, lice have often been there for weeks. In contrast, UC IPM notes that someone who has had lice before can start itching right away.

• Itching, worst at the back of the head and the neck.
• A tickling feeling, as if something is moving in the hair.
• Trouble sleeping and irritability, both on the CDC’s symptom list.
• Small red bumps or sores on the scalp, neck and shoulders from scratching.
• Nits close to the scalp, behind the ears and at the hairline.

People search for “lice bites”, but you rarely see a bite itself. What shows is the scratching: small red bumps on the scalp, behind the ears or at the back of the neck, which Seattle Children’s says can keep itching after the lice are gone. Mayo Clinic notes these bumps look red on white skin and may be harder to see on Black or brown skin. A bump alone cannot tell you which insect caused it, so look for lice in the hair. For itchy bumps elsewhere on the body, our bug bite identification chart covers the other culprits.

How to check for lice, including on yourself

The most reliable check is wet combing: a metal nit comb pulled through wet, conditioned hair in small sections under bright light. UC IPM calls it the best way to inspect for head lice, and the CDC says finding a live nymph or adult is the best way to confirm them.

Checking your own head alone

Plenty of teens and adults have no one to ask, and many feel embarrassed to. You can still check yourself. Sit facing a mirror with a second hand mirror, or prop your phone up and use the front camera. Wet and condition your hair, then comb from the scalp outward in small sections, working by feel around the back.

After every pass, wipe the comb on a white paper towel and photograph it with your phone. Zoom in on the photo rather than squinting at the comb. Then use your phone camera on video, held behind your head, to look at the nape of your neck and behind your ears, which is where nits are most often found.

Can you feel lice crawling?

Sometimes. The CDC lists a tickling feeling of something moving in the hair as a symptom. Even so, it is a poor test on its own, because anxiety and a dry scalp produce exactly the same sensation. After a scare, plenty of people feel crawling for weeks with no lice at all. Only finding a live louse settles it.

Are head lice dangerous?

No. Head lice do not transmit any disease, and the CDC says they are not considered a health hazard. The one real risk is a bacterial skin infection from scratching, which shows up as sores that weep, crust or will not heal. Head lice are a nuisance and a worry, not a medical emergency.

So can lice kill you? No. Head lice do not carry disease, and Cleveland Clinic describes them as mostly harmless. Scratching is the problem to watch, because broken skin can get infected.

Will head lice go away on their own? Almost never. Each female lays several eggs a day, and UC IPM notes that because people stay warm all year, lice keep breeding without a break. Left alone, an infestation grows rather than fading, so it needs treatment.

How do you get head lice?

Almost always through direct head-to-head contact with someone who already has lice. Lice crawl from one head to the next when hair touches, during play, sleepovers, sports or a hug. They cannot hop, jump or fly, and the CDC says getting them has nothing to do with how clean you or your home are.

Less often, lice spread on things that touch the head. The CDC lists hats, scarves, coats, sports uniforms, hair ribbons, combs, brushes and towels, and lying on a bed, couch, pillow, carpet or stuffed animal that an infested person used recently. Since lice die quickly off the head, these routes matter much less than contact.

• Do lice like clean hair or dirty hair? Neither. The American Academy of Dermatology says lice do not care whether hair is squeaky clean or dirty. They want blood.
• Can you get lice from a dog or cat? No. Pets do not get or spread head lice, according to the CDC.
• Can lice jump or fly? No. They have no wings and cannot jump. They only crawl.
• Can you get lice in a pool? It is unlikely. The CDC says lice can survive under water for hours but rarely spread in a pool, and chlorine does not kill them.

Who gets head lice most

Children aged 3 to 11 get head lice most, along with the people who live with and care for them. The CDC cites an estimate of 6 to 12 million infestations a year in that age group in the United States. UC IPM adds that this figure is probably too high, since many cases are misdiagnosed. Girls get them more often than boys, likely because of more head-to-head contact during play.

Adults get head lice too, often from a child in the house. That is why the CDC advises checking every household member, adults included, when one person has lice. A parent who is never checked can pass lice straight back to the kids.

Do Black people get lice?

Yes, but much less often in the United States. The CDC says infestation is much less common among African American people. UC IPM explains why: lice in North America grip hair that is round in cross section, and many Afro-textured hairs are flatter, which is harder for their claws to hold. Still, UC IPM notes that braiding gives lice more to hold onto on any kind of hair, so braids and locs can host them.

How long can lice live off your head?

Not long. An adult louse dies within 1 to 2 days once it falls off a head and cannot feed, according to the CDC and UC IPM. Nits need the warmth right next to the scalp, so the CDC says they cannot hatch and usually die within a week away from it. That is why only recent items need cleaning.

Survival times from the CDC and UC IPM. Freezer method from UC IPM.

So can lice live in your bed? For a day or so, and not in a way that keeps an infestation going. If you are waking up with fresh bites on your arms and body rather than an itchy scalp, the bed points to a different insect. Our guide to bed bugs explains the signs to look for instead.

The head lice life cycle, and why timing is everything

A louse goes from egg to egg-laying adult in about two weeks. Eggs hatch in about a week, 6 to 9 days per the CDC. The nymph then takes about 7 days to mature, and UC IPM says females start laying a day later. An adult lives about 30 days on a head and lays around six eggs a day.

From the CDC, UC IPM and Mayo Clinic. Hatching times vary between sources, from 6 to 12 days.

Those numbers explain the second treatment. On day 0, most treatments kill the crawling lice but miss the eggs. Those eggs hatch over the next 6 to 9 days. Meanwhile, each nymph needs about a week to grow up before it can lay. So there is a short window, around day 7 to 10 depending on the product, when the eggs have hatched and the new lice have not started laying. The CDC says that is exactly when to treat again. Treat too early and some eggs have not hatched. Treat too late and new eggs are already on the hair.

Built from CDC, UC IPM and Johns Hopkins timings. Retreatment day depends on the product: 7 days for benzyl alcohol and dimethicone, day 9 for permethrin, days 9 to 10 for pyrethrins, and only if live lice are seen at day 7 for spinosad. Ivermectin lotion is a single use, so ask a doctor before using it again.

How to get rid of head lice

Combine a treatment that kills the lice with combing that removes the eggs, and repeat on schedule for about three weeks. Start with what costs least. A metal nit comb is cheap and reusable, and UC IPM says many families get rid of head lice with careful combing alone. Medicines come next, chosen with resistance in mind.

First, decide who needs treating

Only treat someone with an active infestation, meaning you have found a live louse. Nits near the scalp with no live louse call for combing and a recheck in 2 to 3 days, or a doctor's opinion. The CDC advises checking everyone in the household and close contacts, then treating every infested person, plus anyone who shares their bed, on the same day. Some popular guides say to treat the whole family whether or not lice are found, but that only adds chemical exposure for people who do not need it.

Option 1: wet combing (cheapest)

Wet combing physically pulls out lice and eggs, so resistance does not matter and it is safe at any age. It works on its own for many families, and it is also the step that makes every medicine work better. The trade-off is time: it needs repeating every 2 to 3 days for about three weeks.

Option 2: dimethicone products

Dimethicone is a silicone that coats lice and blocks their breathing. It is not an insecticide, and no resistance to it has been reported. UC IPM reports that in several randomised trials, 70% to 97% of people using 4% dimethicone were lice-free after two weeks. It is not absorbed through the skin, has very few side effects, and suits all age groups.

Dimethicone products are sold without a prescription. Since the coating makes hair slippery, UC IPM suggests combing while the product is still on. As with other treatments, plan a second application after about 7 days, and keep checking the head for 10 days or more.

Option 3: over-the-counter lice treatments

Besides dimethicone, three insecticide ingredients are sold without a prescription in the US. Permethrin 1%, sold as Nix, is approved from 2 months of age. Pyrethrins with piperonyl butoxide, sold as RID and others, are approved from 2 years. And ivermectin 0.5% lotion, sold as Sklice, is approved from 6 months and is now available without a prescription, according to Mayo Clinic.

Here is the problem many families discover the hard way. Lice in much of the US have become resistant to permethrin and pyrethrins. UC IPM calls resistance the most common cause of treatment failure today and advises choosing other ingredients first. The CDC is more cautious: it confirms resistance exists but says how widespread it is remains unknown. UC IPM also reports resistance to malathion. Either way, if Nix or RID did not work, the product may simply not work on your lice anymore.

Ivermectin lotion works differently. The CDC says a single application on dry hair works for most people, without nit combing, because newly hatched lice cannot survive it. Do not repeat it without asking a doctor.

Option 4: prescription treatments

If a correctly used treatment fails, a doctor can prescribe something stronger. The CDC lists benzyl alcohol 5% lotion and spinosad 0.9% for ages 6 months and up, and malathion 0.5% for ages 6 and up. Spinosad kills eggs as well as lice, so nit combing is not required. For hard cases, doctors sometimes prescribe ivermectin tablets, which the CDC says are not for children under 15 kg (33 pounds) or pregnant women.

Malathion is flammable. The CDC warns against smoking and against electrical heat sources such as hair dryers, curlers, and curling or flat irons while it is on the hair. Lindane, once a common lice shampoo, is no longer sold in the United States because of its risk of serious side effects.

Ages and egg activity from the CDC’s clinical guidance and Mayo Clinic. Dimethicone from UC IPM. Brand names are examples only, not endorsements.

Braids, locs and hair you cannot comb

Combing through braids, locs or extensions is often impossible, and that does not have to mean cutting them off. UC IPM reports that three dimethicone treatments made 5 to 6 days apart can reliably clear lice from hair that cannot be combed, with no nit removal needed. Shaving or cutting hair short is never required, although short hair is easier to comb.

Home remedies: what the evidence says

Most home remedies do not hold up. The CDC says it has no scientific evidence that mayonnaise, olive oil, margarine, butter or similar products work. Johns Hopkins Medicine adds tea tree oil, neem oil, vinegar and saline sprays to the list of remedies without scientific support. Some are also risky.

• Remedy 1

  “Smother them overnight with mayonnaise or olive oil under a shower cap.”

  The evidence: The CDC has no evidence it works, and lice can survive for hours under water. Mayo Clinic says it is not clear how well these products work.

• Remedy 2

  “Tea tree oil kills lice.”

  The evidence: Johns Hopkins lists it among remedies not supported by scientific evidence. Mayo Clinic warns that essential oils are not tested like medicines and can cause allergic reactions.

• Remedy 3

  “Vinegar dissolves the glue on nits.”

  The evidence: Johns Hopkins puts vinegar on the same unsupported list. Conditioner and a metal comb are what loosen nits in practice.

• Remedy 4

  “Douse the hair in rubbing alcohol or Listerine.”

  The evidence: None of the health sources we checked recommends it. Rubbing alcohol is flammable, and Mayo Clinic says never to use anything that can catch fire to kill lice.

• Remedy 5

  “Kerosene, gasoline or a pet flea shampoo will finish them off.”

  The evidence: Never. UC IPM and Mayo Clinic both warn against these, and UC IPM notes serious injuries to children and adults from chemicals not meant for lice.

• Remedy 6

  “A hot hair dryer kills lice.”

  The evidence: Mayo Clinic says not to try, since a dryer can blow lice onto other people. Seattle Children's adds that some lice products are flammable. Clinics use a special heated-air machine instead, run by trained staff.

Why head lice keep coming back

Most repeat cases come from a short list of mistakes, not from bad luck. The CDC names five reasons treatment fails: misdiagnosis, using conditioner before the medicine, not following the instructions, lice resisting the medicine, and catching lice again afterwards. Each one has a fix.

• The second treatment was skipped or mistimed. Eggs hatch after the first dose, so the schedule in the timeline above matters.
• The lice resist the product. UC IPM says if you find live, active lice a day after treatment, switch to a different active ingredient rather than repeating it.
• Someone else still has them. A parent, sibling or best friend who was never checked can pass them straight back. UC IPM recommends that all infested people be treated at the same time.
• The comb-outs stopped too soon. One survivor laying six eggs a day restarts the whole thing.

Cleaning your house after head lice

You do not need to deep-clean the house. Only wash items the person used in the 2 days before treatment, in hot water of at least 130°F (54°C), then dry them on high heat. Seal anything you cannot wash in a plastic bag for 2 weeks, soak combs in hot water, and vacuum where they sat. That is the whole job.

This advice comes straight from the CDC, and it ends a lot of panic. Lice die within a day or two away from a head, so last month’s laundry and the closet are safe. The CDC adds that spending a lot of time and money on housecleaning is not necessary. A new couch does not need throwing out. Simply vacuum it.

• Wash: pillowcases, sheets, towels, hats, scarves and the clothes worn in the last 2 days.
• Bag or freeze: stuffed animals, helmets and headphones that cannot be washed. UC IPM says a freezer at 5°F (-15°C) or colder kills lice and eggs in 10 hours.
• Soak: combs, brushes and hair clips in water at 130°F (54°C) or hotter for 5 to 10 minutes.
• Vacuum: the couch, car seats and the floor where the person sat or lay.

Head lice and school

A child with head lice does not need to be sent home early or kept off school. The CDC says they can finish the school day, get treated at home, and return to class once treatment has started. The American Academy of Pediatrics and the National Association of School Nurses also say “no nit” policies are not necessary.

Why so relaxed? By the time lice are found, the child has usually had them for weeks, so sending them home early protects no one. And as the CDC points out, nits more than a quarter inch out are almost always hatched or dead, so UC IPM concludes that “no nit” rules lack a biological basis. Policies still vary, though, so check your school’s rule, and do tell the school or the parents of close friends so they can check too.

How to prevent head lice

The best prevention is avoiding head-to-head contact and checking heads regularly when lice are going around. No spray, shampoo or scent is proven to keep lice away. Johns Hopkins Medicine says there is no proven head lice deterrent, so the real goal is catching a new case early, while it is small.

• Teach children to avoid head-to-head contact during play, sports, sleepovers and camp, as the CDC advises.
• Do not share hats, scarves, combs, brushes, hair ties or towels.
• When there is a case in the class, check heads often. UC IPM suggests nightly checks with a metal comb during an outbreak.
• Never skip a bike or sports helmet out of fear of lice. Mayo Clinic and Seattle Children’s both say the safety benefit comes first.

When to see a doctor

Most head lice can be treated at home, but see a doctor if a treatment used correctly has not worked, if the scalp looks infected, or before treating a child under 2. Seattle Children’s advises calling if lice are still there after 2 weeks of treatment. A doctor can also confirm whether it is lice at all.

Head lice myths

At least seven common beliefs about head lice are wrong, and a few of them push families into expensive or harmful choices. Here are the ones we see most often, each checked against the CDC, UC IPM and the major hospital guides.

• Myth 1

  “Nits are the size of a sesame seed.”

  Truth: That is the adult louse. A nit is about 0.8 mm, roughly a third of that length, according to UC IPM.

• Myth 2

  “Lice jump from head to head.”

  Truth: They cannot jump, hop or fly. They crawl, which is why head-to-head contact is the main way they spread.

• Myth 3

  “Lice mean dirty hair or a dirty home.”

  Truth: The CDC says getting head lice is not related to cleanliness. Lice live just as happily in freshly washed hair.

• Myth 4

  “You have to wash everything in the house.”

  Truth: Only items used in the 2 days before treatment. Lice die within a day or two away from a head.

• Myth 5

  “Treat the whole family, just in case.”

  Truth: The CDC advises treating people with live lice plus anyone who shares their bed, and checking the rest.

• Myth 6

  “Finding nits means you still have lice.”

  Truth: Nits more than 1/4 inch from the scalp are almost always empty or dead. With no live lice, the CDC says no treatment is needed.

• Myth 7

  “Itching means the lice are back.”

  Truth: Seattle Children's says itching can last after the lice are gone, and worry alone causes it. Only a live louse confirms a new case.

Medical disclaimer. This page is for general information only. It is not a medical diagnosis. If you have severe symptoms, trouble breathing, swelling of the face or throat, fast spreading redness, fever, severe pain, pus, or signs of infection, contact a doctor or your local emergency number.