Head lice: What they look like and what to do about them (2024)

Head lice are tiny parasites that live on the human head – especially the heads of kids in preschool or elementary school, apparently. The Centers for Disease Control and Prevention (CDC) estimates that 6 to 12 million lice infestations happen each year in the United States among children 3 to 11 years old.

Getting a note home from school or daycare about lice making the rounds – or spotting them on your child's head – can be more than a little upsetting. Keep in mind, though, that lice have nothing to do with poor hygiene, and they don't carry disease. You can eliminate these critters and keep them from spreading to other kids.

Here's everything you need to know about head lice.

What do lice look like?

Lice develop in three phases – nit (egg), nymph, and adult louse. According to the American Academy of Pediatrics (AAP), if untreated, the cycle can repeat every 3 weeks, and each louse can live about 28 days.

When checking your child's hair for evidence of lice, you'll want to look for both nits and live lice.

Nits

Nits are the eggs laid by adult lice. (Some experts use the term "nits" only to talk about empty egg casings, but most often "nits" refers to both eggs and empty shell casings). Nits are oval shaped and tiny, about the size of a knot in thread. They may appear yellow, white, or brown (sometimes the same color as the child's hair). Empty nits look lighter.

The female louse lays her eggs (up to 10 a day) a fraction of an inch from the scalp, where it's nice and warm – just right for hatching. She attaches the eggs to human hair shafts with a waterproof, glue-like substance. This ensures that the nits can't be washed, brushed, or blown away, unlike dandruff and other bits of stuff in the hair that often gets mistaken for nits. Body heat incubates the eggs, which hatch in 7 to 12 days, depending on the climate.

Once the eggs have hatched, their yellow or white shells remain attached to the hair shaft, moving farther from the scalp as the hair grows. As a result, empty nit shells attached to hairs are usually found farther away from the scalp than the live eggs.

Nymphs and adult lice

Baby lice, known as nymphs, look like adult lice but smaller, about the size of a pinhead. They're usually lighter in color than the adults. Nine to 12 days after emerging from the nits, they become adults and mate. The females then lay their eggs, and the cycle starts over.

Adult lice are 2 to 3 mm long (1/16 to 3/32 of an inch), about the size of a sesame seed, with six legs. They're tan to grayish white, and they can become darker when they feed. They live and thrive by sucking tiny amounts of blood from the scalp.

An adult louse can live up to 28 days or so on the human head, but will die within a day or two if it falls off. They can be hard to spot because they crawl fast and avoid light.

How do you get lice?

Your child probably picked up lice from an infested sibling or playmate. Lice are crawling insects. They can't hop, jump, or fly, but they can crawl from one head to another when people put their heads together – for example, when they hug or lay their heads on the same pillow.

(Lice can crawl from one head to another, but you can't catch nits. Nits have to be laid by live lice.)

Head lice are common among kids in preschool and elementary school, and their families and caregivers. Some studies suggest that girls get head lice more often than boys. This may be because they have more head-to-head contact with each other and longer hair that provides more warmth and darkness (two things lice love).

"Head lice are most commonly spread from prolonged head-to-head contact – sleeping in the same space, for example," says Shawnté James, M.D., a newborn hospitalist in Washington, D.C. who practices at Pediatrix Neonatology of Maryland at Rockville and is a member of the BabyCenter Medical Advisory Board.

If your child has long hair, it may be helpful to put their hair back in a tight ponytail, braids, or a bun when lice are going around. When hair isn't loose, it's harder for lice to grab on and travel from head to head.

It's a myth that lice are a product of poor hygiene or poverty. Head lice are equal-opportunity parasites. They like clean hair as well as dirty hair and can flourish in even the wealthiest communities. "Head lice aren't an indication of poor hygiene, and they can occur in any socioeconomic community," says Dr. James. "They aren't dangerous from a health perspective."

So, when lice are going around, it's no one child or family's fault. If your child has lice, chances are they're traveling through the neighborhood or school. And your child has probably unknowingly infected others.

Since lice can live for up to a day off of the human head, it's theoretically possible to get lice if your hair makes contact with items such as hats, combs, or brushes that were used recently by an infested person. However, this is much less likely than human-to-human spread. One small study published in the International Journal of Dermatology found that the pillow cases of those infested with head lice only contained live lice 4 percent of the time.

Animals (dogs, cats, and other pets) don't transmit human lice, either, so there's no need to worry about the family pet carrying them around.

Symptoms of head lice

A head lice infestation is called pediculosis. Infestations peak in the fall and in January, though they happen year round.

Your child may not have any symptoms, or they may have one or more of these symptoms:

• A tickling feeling on the scalp/a sensation that something is moving in the hair
• Itching (kids may scratch or rub their scalp, especially around the back of the head or ears). It may take 4 to 6 weeks for the scalp to become sensitive to lice saliva and start to itch, however. And your child may feel itching even weeks after the lice are gone.
• Sores on the head caused by scratching. If your child develops a bacterial infection from scratching, their lymph nodes may begin to swell.
• Irritability
• Trouble sleeping (lice are more active in the dark)
• Conjunctivitis (pinkeye). It's uncommon, but if your child has lice on their eyebrows or eyelashes and scratches and rubs their eyes, it can lead to eye inflammation.

How to check for lice

Spotting sesame-seed-size lice and their teeny eggs is hard – but not impossible. You'll need really good light and a pair of strong drugstore reading glasses or a magnifying glass (unless you have eagle eyes). Here's how to check your child's scalp:

1. Part your child's hair in various places and check their scalp. Don't miss behind the ears or at the nape of their neck. You may notice sores or a rash where your child has been scratching.
2. Look for movement in the hair. You're not likely to see the lice themselves. They're very small, move quickly, and avoid light, so they're difficult to spot.
3. Look for lice eggs, known as nits. These tiny sacs are attached to the hair near the scalp (within a quarter inch if they haven't yet hatched). Nits may be easier to feel than to see – they'll feel like grains of sand.
4. Make sure the nits you find are still alive. If the only nits you find are more than a quarter inch from the scalp, they may have already hatched and your child may no longer be infested. (Nits can only hatch in the warmth right next to the scalp. After they hatch, the empty egg remains attached to the hair and grows farther and farther from the scalp.) Only viable nits – those very close to the scalp – or live lice are proof of a current infestation.

If you can't tell whether there's an infestation by doing a visual inspection, you'll want to wet comb your child's hair. Wet combing involves applying conditioner to your child's hair and then combing the hair out in sections, from the roots to the ends, using a fine-toothed lice comb. (The teeth on a regular comb are too far apart to nab the tiny lice.)

You'll find detailed instructions for wet combing in our article on lice combs and how to use them.

If you're still not sure whether your child has head lice, your healthcare provider can help with a diagnosis.

What to do if your child has lice

Just take things one step at a time. Remind yourself that the critters don't carry disease and won't physically hurt your child (though your child can get a skin infection if they scratch a lot, so don't let an infestation continue). Calmly reassure your child that this can happen to anyone and that you'll take care of it for them.

Your main to-do's: start treatment, check the rules on lice at school or daycare, and clean some household and personal items.

Treatment and prevention

Set up a time to give your child a lice treatment as soon as possible. Check the other kids and adults in the house, too. Everyone with an infestation will need to be treated. Children with an infestation should avoid head-to-head contact with siblings (sleeping together, for example) until the lice are gone.

School or daycare rules

If your child has lice, do they need to stay home from school or daycare? It depends.

The CDC says, "Students diagnosed with live head lice do not need to be sent home early from school; they can go home at the end of the day, be treated, and return to class after appropriate treatment has begun."

But schools and childcare facilities have different policies surrounding head lice. These policies are usually determined by school boards, and local health departments may also have guidelines.

Some schools and childcare centers have a "no-nit policy," which is also supported by the National Pediculosis Association. The AAP and the National Association of School Nurses, however, recommend discontinuing these policies. They point out that many nits are far from the scalp (making them unlikely to hatch) and that nits are unlikely to be transferred. In addition, misdiagnosis of nits is common. "The burden of unnecessary absenteeism to the students, families and communities far outweighs the risks associated with head lice," says the CDC.

The AAP recommends that children remain in class and try not to have close direct head contact with others (though it's also important not to stigmatize a child with lice). They also recommend that parents be notified immediately so they can start treatment.

Cleaning household and personal items

There's no need to spend a lot of money or time on special housecleaning. Lice won't survive long off a person's head. But to be extra sure no stray lice survive, take these added measures:

• Wash hats, scarves, bedding, clothing, and towels used by the infested child in the last two days. Use hot water to wash and hot air to dry. It takes just 5 minutes for lice to be killed by heat over 128.3 degrees F. If there are items that can't be washed, have them dry cleaned or put them in a sealed plastic bag for two weeks. Another option is to freeze the items (in a freezer or outdoors). "Head lice will die in a freezer set at 0 degrees F within 10 to 12 hours," says Dr. James, "but I recommend 24 hours to be safe."
• Soak combs and brushes in hot water (at least 130 degrees F) for 5 to 10 minutes.
• Vacuum furniture and floors to pick up hairs that might have viable nits attached to them.