Lice Shouldn't Keep Kids from School, Doctors Say

Head lice are annoying, but they don't actually make people sick, and children with the condition should not be kept away from school, according to new guidelines from a leading group of pediatricians.

The guidelines, from the American Academy of Pediatrics, say that although head lice can cause itching, they are not known to spread disease, and the insects are not very likely to spread from one child to another within a classroom. Rather, it is usually direct head-to-head contact that spreads lice.

For this reason, "no healthy child should be excluded from school or allowed to miss school time because of head lice or nits," the guidelines say. (Nits are the eggs of head lice.) Most doctors who care for children agree that school policies requiring children to be free from nits before returning to school should be abandoned, the AAP says.

In addition, screening kids at schools for head lice does not reduce the occurrence of the condition in classrooms over time, so routine screenings at schools should be discouraged, the AAP says. However, parents should still regularly check their children for head lice, and school nurses may check children who have symptoms of lice. 

Once a person is diagnosed with head lice, everyone in the family should be checked for the condition, the AAP says. Lice are usually transmitted by direct contact, so it's less likely that people will get lice from touching household items, but it is still wise to clean all hair-care items and bedding used by the person who had lice, the guidelines say.

It is recommended to teach children not to share items such as combs, brushes and hats, although such precautions are unlikely to prevent all cases of head lice, the AAP says.

Kids shouldn’t be sent home for lice, but schools can’t ignore the issue either

Last night, my 3-year-old daughter made soft, singing noises while she dipped a plastic boat in and out of the bubbles of her bath, oblivious to my actions of raking a fine-toothed metal comb through her mop of curls that reach her shoulders when they are wet.

Just a few months ago, the sight of a hairbrush in my hand caused her to shriek. Bath time was a battle. I was certain her first memories would be the pain from my tugging tangles out of her hair. Then, that fateful day came when the sun shone on her little forehead, still from sleep in her car seat. I bent over to carefully unbuckle her and saw the telltale bug crawling through her blond curls. Head lice.

I was no stranger to this terror. My oldest daughter seems to attract them. Maybe it is her mass of light-brown hair, so thick I can barely get a comb through it. Maybe it is her many invitations to sleepovers with several friends where they try on five different outfits. When I first discovered my oldest had them, my youngest was a newborn. I was on my own, barely making ends meet, scrambling to find work I could do at home to pay rent. Dropping $20 on a tiny bottle of shampoo that claimed to kill the bugs that had invaded our house was an expense I could not afford. Plus, I had to wash and dry everything I could — including stuffed animals — on high heat, vacuum, and repeat a week later. I bagged most of it instead.

My oldest had been in kindergarten that year, and I faintly remembered a line in the classroom newsletter telling me they had a report of lice. There was not any mention of ways to check for it, or how to prevent it. This was several years ago, when the school nurse came around with her flashlight to check every head. I knew if she found any, she would send those kids home because of the district’s “No Nits” policy. So, I didn’t worry. Lice happened to other people. Not my daughter, who stayed in the bath so long, her fingers wrinkled before I convinced her to get out of the tub.

When I found lice last spring, I sent an email to my daughter’s teacher. I half expected her to tell me that, even though I had used the shampoo and spent an hour combing her hair, my daughter would have to stay at home until the nits were gone. The school nurse called me instead.

“We don’t send students home anymore,” she cheerfully said, explaining that only 10 percent of lice are transferred at school. Because of this, they no longer checked students, did not call parents to pick up their children and did not notify the parents there had been a report. My daughter’s teacher did not send out a note, email or even include the infestation in the newsletter that week.

I applauded the idea of not sending children home. Low-income families don’t need the added hardship of missing work on top of the expense of ridding themselves of lice and nits, along with the stigma their kid would experience of being the one with cooties. The expense of lost wages, in addition to the added expense of laundry and buying shampoos and kits, could mean less rent money, not just an inconvenient afternoon. But shouldn’t there be a system in place to notify parents in the chance their child is part of that 10 percent?

As kids are back in school, connecting with friends, and putting their heads together, either by taking selfies or studying, lice transferring from one head to the next seems inevitable. But there was no mention of that possibility in the student handbook my daughter’s school sent home.

In deciding to allow students who have lice to come to school, the flip side should be educating parents on what to look for, how to prevent them and how to get rid of them without spending $50 on chemical-laden shampoos, salon treatments and loads of laundry. Keeping lice out of schools should be a herd immunity type of attitude. Schools should send home brochures with a plastic comb attached in an envelope. If every parent knew that the best way to prevent lice from spreading is by looking for them, cases decrease dramatically.

Nobody wants to admit their kid is the one with lice. Not only because of the work involved in getting rid of them, but because lice are still associated with dirt, grime, neglect and often poverty. Yet, when stomach bugs run rampant, we all accept that it will run its course and we will be spending a day doing laundry along with everyone else. If parents admitted they are part of the 6 million to 12 million cases of lice reported a year, maybe it’ll be on par with stomach bugs, and not shrouded in secrecy.

More than that, I want a way for parents to notify the school their child has lice, anonymously if needed. I want to get a text message every time this happens so I know to check more than once a week for a while. If parents know how many times others are finding lice on their kids’ heads, maybe other parents will not hide their own discoveries in shame.

NYC Schools have a “No Head Lice” policy.

Can my child go to school with head lice?

• NYC Schools have a “No Head Lice” policy. Students who have live head lice are not allowed to go to school until they are lice-free. Students with nits are still allowed to attend.

• Students may return to school the day after treatment for head lice as long as there are no live lice upon re-inspection by designated school personnel. 

• Students will be re-inspected by a school worker 14 days after the treatment to make sure there are no live head lice.

What are head lice?

• Head lice are small insects with six legs. They are usually the size of a sesame seed (the seeds on burger buns). 

• Lice live on or very close to the scalp. They won’t wander far down the hair shafts for very long. 

• Lice can only live on human beings; you can’t catch them from animals. 

• Nits are not the same thing as lice. Lice are the insects which move around the head. Nits are egg cases laid by lice. Nits are smaller than a pin head and are pearly white. 

• If you have nits it doesn’t always mean that you have head lice. When you have got rid of all the lice, the nits will stay stuck to the hair until it grows out. 

• You only have head lice if you can find a living, moving louse (not a nit) on the scalp.

Are head lice contagious?

• Anybody can get head lice by coming into contact with an infected person, but spread of head lice requires direct head to head contact. Head lice can’t swim, fly, hop or jump. 

• Head lice can be spread as long as lice or eggs remain alive on the infected person’s clothing. 

• Head lice are generally caught from close family and friends in the home and community, and not from the school.

Can head lice be prevented?

• The best way to stop a head lice infection is for families to learn how to check their own heads. This way they can find any lice before they have a chance to breed. 

• Instruct children not to share hats, combs, and brushes. They should avoid touching an infested person’s unlaundered clothing and bedding. 

What are the symptoms? 

• Head lice symptoms often start to appear 2 to 3 weeks after the head lice infection. Usually, the first indication of an infection is itching or scratching in the area of the body where the lice feed. Examine your child for head lice if (s)he is scratching at the back of the head or around the ears. Examine your child for crab lice if (s)he feels itchy around the genital area. 

What do I do if I suspect my child has head lice?

• Check Your Child’s Head for Lice

• Wash your child’s hair well and then dry it with a towel. The hair should be damp, but not dripping. 

• Make sure you have good light. Daylight is best. 

• Comb the hair with an ordinary comb. 

• Using the teeth of a fine tooth comb, touch the skin of the scalp at the top of the head. Brush the comb carefully towards the edge of the hair. 

• Look carefully at the teeth of the comb in good light. 

• Do this over and over again from the top of the head to the edge of the hair in all directions, working around the head. 

• Do this for several minutes. It takes at least 10 to 15 minutes to do it properly for your child’s head. 

• If there are head lice, you will find one or more lice on the teeth of the comb. 

• Head lice are little insects with moving legs. They are often not much bigger than a pin head, but may be as big as a sesame seed (the seeds on burger buns). Nits are smaller than a pin head and are pearly white.

• If your child only has nits (lice eggs) make sure you have brushed them all out with the fine tooth comb. 

• Read the next section for what to do if your child has adult lice (not nits). 

If you Find Adult Lice (Not Nits) 

• Treat All Family Members Who Have Lice.

• Check the heads of all the people in your home. 

• Only treat the people who have living, moving lice (not nits). If a family member has nits, carefully brush them out with a fine-tooth comb. 

• Treat all of the people in your home who have adult lice at the same time. 

Get the Lice Out of Your Home

• Clean all bedding, towels and clothing from the infected individual with soap and hot water (140 degrees F). Place them in a dryer for at least 20 minutes to help kill any remaining lice. 

• Dry-clean all clothes that need to be dry-cleaned. 

• Seal the infested individual's stuffed toys, and other infested items that can’t be laundered, in a plastic bag. Leave them for 10 days to allow all lice to die of starvation. 

• Get rid of, or soak combs and hairbrushes in rubbing alcohol or the medicated shampoo used to kill lice. 

• Throw out any hair accessories, such as hair elastics and ribbons. 

• Thoroughly vacuum carpets and upholstered furniture. 

• Pets cannot become infested with head and body lice, so no precaution is required.

Got Lice? Come On In.

My kids’ school lets students with head lice stay in class. What a great policy!

If you’re a parent, you’ve probably gotten the dreaded call from the school nurse, letting you know that your child has lice. It happened to our older daughter in kindergarten, and then again two years later when our youngest was in the same grade. Each head lice infestation was a mini nightmare: a work and school day lost to early pickup, chemical shampoos, vacuuming, and endless combing for nits (eggs). The days after, spent worrying that a stray louse might mean another call from the nurse and another day out of school. And that call always came: Your daughter has lice again. She’ll be waiting for you in the office. Last year we spent a couple hundred dollars on a proffesional lice remover, just because we could no longer face the hours every night we needed to spend nit-picking.

At many schools, any discovery of live lice in a child’s hair warrants a phone call and the immediate removal of the child from school. At some schools, the child may return the next day if the parents have treated the child’s hair—that is, shampooed it to kill live lice. But in schools with “no-nit” policies, a child can’t return unless every last tiny louse egg has been combed from her hair—and schools may check returning students and send them home if any nits are found.

But then, this fall, everything changed. The schools here in Arlington, Va., have adopted what you might call a live-and-let-lice policy. No child will be sent home for lice or for nits. If a child has lice in her hair, the nurse will contact parents but send the child back to the classroom for the rest of the day. Parents are expected to treat the lice, but no one is checking in to enforce this expectation. No classes or groups will be screened for bugs. “No healthy child,” the policy reads, “should be excluded from or miss school because of head lice.”

When I told friends in other school districts about the shift in our school’s lice plan, their jaws dropped. That’s amazing, they said. Finally, they said. And, How can I persuade my school to do the same thing? But my friends are gross, so you may, understandably, have a different reaction to this news. Like, Ew, a school is letting a bunch of bug-covered, itchy kids rub heads in the classroom?

Sorry, your response is wrong. Arlington’s new stance on lice is being adopted by schools all over the country, encouraged by the American Academy of Pediatrics and then National Association of school Nurses. And its the right one. Lice are not particularly contagious, they hurt basically no one, and they’re not a public health risk. Lice don’t actually matter. It’s high time that squeamish parents and school administrators stop acting like they do.

Let’s start with many schools’ long-standing no-nits policies—policies that say kids can’t return to school unless every last tiny louse egg has been combed from their hair. “No-nit policies don’t make any medical or scientific sense,” said Dr. Barbara Frankowski, professor of pediatrics at the University of Vermont. Frankowski, the lead author of the American Academy of Pediatrics’ study recommending changes in school lice policies, told me that, as any parent who has tried to remove nits knows, the eggs are firmly cemented to a child’s individual strands of hair. “They’re not going anywhere,” she said, “and pose no risk to other children.”

But even parents who understand the logic of not checking endlessly for nits get nervous about sending a child upon whom the nurse has just discovered live lice back to the classroom for the rest of the day. Shouldn’t those children go home so they won’t spread the lice to other kids? “If you find live lice during the school day, it’s likely that child has had lice for weeks,” said Carolyn Duff, the president of the National Association of School Nurses and the nurse at an elementary school in Columbia, S.C. “Allowing that child to remain in the classroom for a few more hours is not putting children at risk.”

After all, despite what you may think, “It’s not that easy to get lice!” Duff exclaimed. “They don’t fly. They don’t jump. They can barely crawl through your scalp. They can only spread through head to head contact, and children in schools don’t usually have head-to-head contact.” Even transmission through hats or hairbrushes is difficult—it can happen in families where such sharing is commonplace, but much less frequently in schools. (According to the experts I talked to, children are much more likely to spread lice during sleepovers or playdates, or at sleepaway camp.)

And even if they were highly contagious: The point that both the AAP and the NASN want to make is that it’s far more important to keep kids in school than it is to send them home in the hope of stopping the spread of lice. Because, again, lice don’t hurt anyone. “We’ve heard stories of kids missing weeks of school because of lice, even being held back a grade,” said Frankowski. “It’s unfair to kids. It’s unfair to parents who work or who have other difficulties that don’t allow them to go through hours of delousing.”

If your school still sends kids home for lice or (God forbid) for nits, what can you do? Find out who makes the decisions on those policies. Sometimes it’s a school-by-school choice, which means you can collect all the relevant scientific information and talk to your principal. (Consider enlisting your school nurse, who almost certainly agrees with you, to help argue the case.)

Sometimes these policy decisions go through the school board. “I don’t want to disparage school boards,” said Frankowski. “But they don’t always make policy connected to what’s scientific—sometimes it’s just what’s easiest, or what they think parents want.” So you need to convince your school board that what parents want is a policy based on science, on expert recommendations, and on making life saner for busy parents.

Who would possibly disagree? Well, there are definitely parents who do. They can find support from Deborah Altschuler, the president and co-founder of the National Pediculosis Association, a nonprofit with a website touting the benefits of no-nit policies. In a phone interview, Altschuler told me that the school policy question was “a minefield” and said there is “a small club of people who follow the idea that there is some kind of scientific basis for allowing children with lice back in school.” She disagrees: “It’s a communicable disease that is easily transmitted among kids. We want to send kids to school lice- and nit-free, rather than lowering our standards to accommodate those who can’t do it for whatever reason.”

When I asked Altschuler about the AAP and NASN’s rejection of no-nit policies, she accused the organizations of being overly influenced by lice-chemical manufacturers. (For what it’s worth, Altschuler funds the anti-chemical National Pediculosis Association  through sales of the LiceMeister nit comb.)

Altschuler’s claim that lice transmit disease—that they are, themselves, a disease—is not supported by most scientists. In general, experts say, parents stress out way too much about head lice. “Head lice are a fact of life. It happens. It’s not a health issue, really,” said Marian Harmon, the school health bureau chief for Arlington County’s public health division who signed off on our schools’ new policy. “It’s not a sign of poor hygiene. It’s not an infection. It’s not a communicable disease. We treat it for the comfort of the child and the family. It shouldn’t be escalated to such a high priority.”

What I wondered after talking with all these experts is whether lice even need to be treated at all. Treatment’s expensive, it can expose your kids to pesticides, it takes forever, and all it does is rid your child of a basically harmless pest—and then only until the inevitable next time it shows up. I certainly didn’t get any of the experts I spoke with to come right out and say that you can pretty much ignore lice. They all note that parents want their children to be lice-free, regardless of whether the lice pose any actual threat. “It’s an emotional issue!” allowed the NASN’s Duff. “It’s a live bug crawling on the head of your child.” But I wonder if emotions aren’t getting in the way of common sense. After all, as Frankowski wryly noted, “No one’s ever died from a head louse infestation.”

That’s what I often found myself muttering in years past, as my wife and I spent work days and weeknights washing and combing and washing and combing the heads of perfectly healthy children. In an educational environment in which intervention is the default, a message from a school district announcing that its new policy is for everyone to just relax is extremely welcome. My kids need to be in school to learn, and to play with their friends, and to build their bright futures, and to stay out of my hair. I don’t need them sent home because of the harmless things crawling in theirs.

Smartphones blamed for the dramatic rise in head lice as schoolchildren gather together to view the screens

Smartphones have been blamed for a dramatic rise in head lice among schoolchildren because they encourage youngsters to gather round in groups, allowing the bugs to jump between heads.

A study of more than 200 youngsters found those owning a smartphone - or tablet - were more than twice as likely to be infested with lice.

Out of the 98 who did not have or use either type of device 29 (29.5 per cent) experienced head lice - compared to 65 of the 104 (62.5 per cent) who did.

Almost half of the participants had lice at some point in the previous five years, up to 22 times more than the figure of two to eight percent that has been calculated in the past.

However taking regular selfies was not a major factor in the rise contrary to previous suggestions.

In 2015, Wisconsin GP Sharon Rink coined the phrase 'social media lice', claiming the upsurge in head lice was caused by group selfies, which caused friends to bump heads. 

Dr Tess McPherson, of Oxford University Hospitals NHS Foundation Trust, said: "Compared to previous estimates of head lice incidence our figures were much higher, showing that almost half of children have had them in the last five years, which may not come as a surprise to parents.

"We also noted that children with smartphones or tablets were more likely to get head lice, which is interesting but we can only guess that this is due to the way that young people gather around them, though there could be other reasons.

"Selfie culture gets its fair share of negative press so it's worth noting that despite previous speculation it seems that selfies can't specifically be blamed for helping the spread of head lice at this stage."

The study presented at the British Association of Dermatologists annual conference in Liverpool said previous estimates of the prevalence of head lice in British children "may be conservative."

It found 91 (45 per cent) of the children had had head lice in the last five years, a longer period than covered by earlier research.

Girls with siblings aged six to nine were most commonly affected.

Matthew Gass, of the British Association of Dermatologists, said: "Head lice are a pain to deal with, both for children and their parents.

"Speaking from experience, they are intractable misery bugs that take far more time and effort to remove than is reasonable.

"Not to mention the obligatory quarantine period that they necessitate. That's why a better understanding of how these pests are transmitted is useful.

"Prevention is always better than a cure, particularly if the cure means wrenching your poor daughter's hair with a fine-toothed nit comb, or relying on over-the- counter remedies that head lice are increasingly resistant to.

"We're not saying that smartphones are causing children to get head lice, but that there is a link, so if there's an outbreak at home or at school, consider how electronic devices might cause children to congregate, allowing head lice to spread."

In the study questionnaires were given to parents or guardians attending the paediatric outpatient department at the John Radcliffe Hospital in Oxford, over a one-month period.

The survey collected information on sex, hair length, socioeconomic status and smartphone or tablet ownership.

Head lice live in hair and are particularly common in four to eleven year-olds - causing an itchy scalp and general discomfort.

They range in size from the size of a pinhead to that of a sesame seed and are a whitish or grey-brown colour.

A variety of treatments to get rid of head lice are available to buy from pharmacies, supermarkets, as well as online and you don't usually need to visit your GP to tackle the problem.

You catch them via direct head to head contact, where they climb from one person's hair to another's - they cannot jump, swim or fly.

They are very unlikely to be spread by items such as combs, hats or pillows and are specific to people - you can't catch them from animals.

Contrary to the old wives' tale, head lice have no preference for dirty or clean hair - nor short or long. They usually die within 12-24 hours of being removed from hair.

The Things Head Lice Carry: Stigma and hassle, but no harm

Add lice to the list of four-letter words that make people cringe. The wingless parasites are itchy and bothersome, and an infestation is often embarrassing to admit and challenging to conquer. But at least head lice have something going for them that a lot of other bugs don’t: They’re harmless.

“Ticks can transmit Lyme disease; mosquitoes transmit West Nile virus and malaria, among other things,” said Navy Capt. Kevin O’Meara, a physician and chief of pediatrics at Fort Belvoir Community Hospital in Virginia.

“But head lice – those guys are pretty benign,” O’Meara said. “They’re not dangerous. They’re just annoying.”

Three types of lice afflict humans. Pediculus humanus capitis, or the head louse, is common in childhood. Up to 25 percent of all school-age children will have head lice at some point, according to the Centers for Disease Control and Prevention, with anywhere from 6 million to 12 million cases reported each year in the United States in children ages 3 to 11.

As O’Meara explains, head lice don’t jump or fly. Instead, they crawl from one person’s head to another person’s. Less commonly, lice also can be transmitted through sharing personal items, such as towels at swim meets and pool parties, and pillows and other bedding at sleepaway camps.

Head lice live on the human scalp, where they eat meals of human blood and attach their eggs, or nits, tightly to the hair shaft. It takes seven to 10 days for the nits to hatch into baby lice, scientifically known as nymphs. The nymphs mature into adult lice anywhere from nine to 12 days after hatching, the CDC says. The sesame-seed-sized critters can live up to about a month on a person’s head.

“It may not be readily apparent that you have head lice,” O’Meara said. “Once you become sensitized to their saliva, you’ll start feeling very itchy. But that may be weeks after that first louse has crawled onto your scalp.”

O’Meara said it’s fine to see a health care provider for help getting rid of lice, but effective over-the-counter medications are also available. 

“Basically, you massage the medication into your hair, let it sit for at least 10 minutes, and then wash it out,” O’Meara said. “Generally, you don’t need to be treated again, but a lot of people do so after seven days because of fear of reinfestation.”

Head Lice Are Becoming More and More Resistant to Lice Shampoos and other Insecticides

Interesting article in SciAm about the difficulty in treating head lice infestations. “Overexposure to insecticides has bred resistance in the parasites, making it harder than ever to treat infestation." The situation is different in Europe, where they've stopped using insecticides to kill lice and nits and use synthetic oils:

Further confounding matters, the co-pay for visiting a doctor, plus the cost of prescriptions, which may or may not be covered by insurance, can impede patient access to these newer medications. And despite their diminishing efficacy, over-the-counter lice shampoos remain the first response recommended by most doctors, health plans and even the American Academy of Pediatrics.

The situation is totally different in Europe, where treatment moved on from pyrethroids and virtually all insecticides about a decade ago, says Ian Burgess, president of Internationals Society of Phthirapterists (people who study lice). Instead most Europeans now rely on silicone and other synthetic oils to eliminate head lice.

The oils envelop the lice, preventing them from excreting water. As liquid builds up inside the louse, its internal organs start to shut down from the exhaustion of trying to pump out the water. Either it dies of this exhaustion", Burgess says, “or its guts rupture from the liquid.”

The Latest on Head Lice

Like many other parents, I’ve paid my dues when it comes to head lice. It was a while ago, back in day care, and there was a dress-up box with hats and crowns and helmets that was probably the smoking gun. We all had to do the whole routine, applying insecticide rinses to our children’s heads and washing sheets and pillow cases in hot water, and becoming somewhat fanatical about not sharing hats.

Meanwhile, my parents, who had grown up in New York tenements, were vaguely horrified that their affluent privileged grandchild was acknowledged to have what they thought of as a mark of disgrace, an infestation that went with poverty and dirt.

And yes, eventually I became convinced that my own head was itching, and bought my own bottle of rinse, though I suspect I was by that point treating phantom lice. Since then, I have checked many heads in the exam room, and I have seen kids with lice, kids with nits, and kids with nothing much going on in the lice department — and I have learned to suppress the phantom lice response; I wear gloves and I wash my hands.

One aspect of the confusion around head lice is that we may think of them as “infectious” because they are spread from person to person — but they do not actually carry infections. They’re just bugs, and technically, we call head lice an infestation rather than an infection, but that doesn’t necessarily make anyone feel any better. (Body lice are different — they can indeed spread infections, most famously typhus).

So when it comes to head lice, the pediatric role in recent years has largely been to reassure, to beg for calm, and to try to get kids back to school as quickly as possible.

The American Academy of Pediatrics put out its latest clinical report on head lice in 2015, a joint project of the group that focuses on school health and the committee on infectious diseases. The report reiterated longtime pediatric positions, emphasizing the importance of careful diagnosis, by trained observers, and arguing first and foremost that children should not miss school because of head lice or nits.

“Misdiagnosis is really common, even with medical personnel,” said Dr. Mary Anne Jackson, the director of infectious disease and professor of pediatrics at Children’s Mercy Hospital in Kansas City, Mo., who works with the A.A.P. committee on infectious diseases.

She said administrators at one school she worked with worried that its football field might be a source of lice, and were concerned with fumigating or otherwise disinfecting it. But unless the players are sharing helmets they are unlikely to transmit head lice.

There are many misunderstandings about head lice, Dr. Jackson said, including the persistent idea that a child with head lice is evidence of an unclean home. (Head lice are, in fact, one of the great equalizers; just look at all the high end “salons” offering to pick to child’s nits for a hefty fee.)

It’s not necessary to treat all the children in a classroom, or all the people who live in the house, though anyone who shares a bed should get treated. We no longer use some of the more toxic insecticidal drugs that used to be employed, like lindane, which was a potential neurotoxin. The over-the-counter preparations that are available now are much safer, but there are concerns about resistance, so many people resort to prescription drugs. One that is commonly prescribed is topical ivermectin, a drug with what Dr. Jackson called “a strong safety portfolio,” but it can be expensive.

And there are many treatments out there that have no evidence to back them up. For example, Dr. Jackson said, there are clinics using heat on children’s hair, which may work under certain conditions, but there is no regulation of how it is being used “to quote unquote inactivate the lice,” she said. “I am skeptical.”

And then there are the “suffocation treatments,” from olive oil to mayonnaise, applied to the hair in hopes of killing off the insects without resorting to chemicals and insecticides. Some of these probably work some of the time but “all will work no matter how you place them if you don’t have lice,” Dr. Jackson said.

So diagnosis is key — someone experienced should look at the child’s head, looking for lice and not just for nits, since all kinds of debris in the hair can be mistaken for nits; everything from dandruff to dirt to drops of hair care products. And someone who knows the resistance patterns in your area should advise you about whether to use the over the counter preparations or the prescription medications.

The head louse life cycle takes about three weeks; the adult female, about the size and color of a sesame seed, lays about 10 eggs a day, and glues each one to a hair near the scalp. Eggs hatch in about nine days, warmed by body heat emanating from the scalp, and the larvae then leave the egg case (which remains glued to the hair, though it’s now empty) and go through several different developmental stages over the next nine to 12 days, before reaching adulthood and starting to lay their own eggs.

That’s why it can be helpful to treat more than once, usually after about nine days, if you are using a product that does not kill the eggs, or if you see live lice after a first treatment. And there are indeed some lice that are resistant to some insecticides, so it’s important to know what is common in your community.

Removing nits with a fine-toothed comb can be done after treating the child’s head, and usually is most effective when the hair is wet, though still not a short or simple process.

From an infectious diseases point of view, Dr. Jackson compared head lice with pinworms, another parasitic infestation parents regard with fear and sometimes with shame, and which may be treated repeatedly without a firm diagnosis that establishes beyond question the presence of these unwanted passengers on the child’s head — or the child’s tail. People worry, kids get treated, sometimes repeatedly, and the treatments cost money and take time. We spend a billion dollars a year on treatments for head lice, according to the American Academy of Pediatrics.

The A.A.P. has fought hard against “no nit” policies in schools, in the interest of reducing the school absence associated with head lice; the C.D.C agrees, and schools are increasingly unlikely to exclude children for nits, but still, in some schools, the policies persist.

“There should never be a case for a child with head lice spending days out of school,” Dr. Jackson said. “Families should be notified, they should be able to access topical medication and they should be able to re-enter the next day.”