Scour That Scalp: Some Lice Eggs Linger Before Hatching

Here’s some lousy news for parents of itchy-headed kids: Lice eggs can take 2 weeks to hatch in human hair, making standard 7-day delousing treatments ineffective in some cases. New research shows that if conditions are right, the eggs, called nits, can sit dormant during treatment, only to pop later and reinfest the scalp. A third application may be necessary after 14 days to eliminate any slow-hatching nits, they say.

Lice don’t lay their eggs directly on skin—instead, they deposit nits at the base of hair shafts. The timing of louse hatching on a human head is difficult to track because adult lice lay eggs continuously, obscuring earlier hatches, and the effectiveness of traditional insecticides on eggs is variable. Previous estimates of how long nits remain viable did range up to 14 days, but much of that work dated to the 1920s and 1930s, when researchers reared body lice inside boxes strapped to a person’s arm or ankle. More recent work relies on head lice raised in lab incubators, which are more stable than the wide range of temperatures and cleanliness found on a human scalp.

For a more reliable estimate, medical entomologist Ian Burgess of Insect Research & Development Ltd. in Cambridgeshire, U.K., analyzed data from 20 previous studies of treatments that kill lice through physical means, such as lotions that suffocate the insects, but do not kill eggs. They didn’t include insecticide treatments because lice across the United Kingdom have developed resistance to standard drugs, Burgess says, leading more doctors to try a brute-force approach that does not rely on insecticides.

The data from 1895 patients revealed cases in which technicians found newly hatched louse nymphs on the 14th day after treatment began, even though the second scalp application had occurred 7 days before. “Some [nymphs] had emerged only an hour or two before checking,” Burgess says. To rule out cases where re-infestation from another child had occurred, or where a few adult lice had escaped treatment, he excluded cases with lice that appeared older than the number of days since the last treatment. Nearly two dozen cases remained—enough to verify that a handful of nits can outlast standard treatment protocols, Burgess reports in an upcoming issue of Medical and Veterinary Entomology.

Although the treatments themselves may play a role, a person's scalp temperature is likely to be the most important factor in how long it takes eggs to hatch, Burgess says. Location and hairstyle matters, too: Lice develop faster at warmer temperatures, so they will hatch more quickly when laid on the warm, thick hair at the nape of the neck than on the thinner hair on top and in front of the scalp.

The analysis is the most rigorous yet to quantify louse hatching times, says Rich Pollack, a public health entomologist at Harvard University. “It should be considered by those who are trying to make a management treatment decision,” Pollack says, observing that just a small number of patients are likely to need a third dose.

New oral insecticides may render the question of hatching times moot, Pollack notes. Those drugs, now available by prescription in the United States, are up to 85% effective at killing lice and eggs with one dose, sparing parents from dousing a squirming child's scalp multiple times.

Tale of Human Origins, Told by Lice

Researchers itching to understand how modern humans evolved are turning to lice for answers. A genetic analysis of head lice suggests that two species of early humans had close physical contact after millennia of isolation, information that may help anthropologists narrow the possibilities for the origin of humans.

According to one theory, Homo sapiens migrated out of Africa and quickly replaced other human species, such as H. erectus in Asia, without interbreeding. The competing theory of "multiregional evolution" contends that modern humans appeared when Homo sapiens from various geographical regions mated with each other as well as with archaic Homo populations, blurring regional and species boundaries. A middle-ground proposal suggests that as modern humans from Africa spread across the globe, they interbred with other archaic humans, but that only African genes persisted. After analyzing the genes of lice, Dale Clayton, an evolutionary biologist at the University of Utah, Salt Lake City, says that the history of these pests best fits the third hypothesis.

Clayton and postdoc David Reed, now an evolutionary biologist at the University of Florida, Gainesville, compared mitochondrial DNA from lice, primarily Pediculus humanus, to published data on human evolution. The data reveal that two genetically distinct lineages of P. humanus appeared about 1.18 million years ago, Reed, Clayton, and their colleagues report online 5 October in the Public Library of Science, Biology.

Clayton argues that the two subgroups must have diverged when two human lines--perhaps Asian H. erectus and the African ancestors of H. sapiens--went their separate ways, which anthropologist believe happened at about the same time. The fact that the lice evolved into subgroups suggests that they had little or no contact with each other, which implies that their human hosts were also isolated--contrary to the multi-regional hypothesis.

But the data do suggest that there must have been some contact among different kinds of early humans. Today, there is only one species of human--but two subgroups of lice. So the lice thought to have been living on H. erectus must have jumped to H. sapiens at some point before H. erectuswent extinct, perhaps as late as 30,000 years ago, possibly through fighting or sex, and that conclusion weakens the African replacement idea.

Milford Wolpoff of the University of Michigan, Ann Arbor, author of the multi-regional hypothesis, doesn't agree with Reed and Clayton's interpretation, calling the new study a "fringe explanation." But paleontologist Chris Stringer of the Natural History Museum in London is quite pleased with the work as it provides "an indirect but informative new window on ... modern human origins."

Gorillas Gave Us the Itch

Among primates, humans have the dubious distinction of having not one, but two types of sucking lice--one that nests on the head and the other that calls pubic hair home. Where did these buggers come from? A new study suggests that while we've been sharing head lice with chimps since before we were even separate species, pubic lice came from gorillas--and not very long ago.

Each year, 3 million people in the United States catch a case of pubic lice, otherwise known as "crabs." It's an important public health problem, but evolutionary biologist David Reed of the Florida Museum of Natural History in Gainesville prefers to look at it as an evolutionary conundrum. Typically, lice share the same evolutionary history as their hosts. For example, if a population of hosts splits into two and each of the isolated populations begins to evolve into separate species, then the parasites evolve too. Human head lice, for example, share a common ancestor with a chimp-based louse, and the two lice are closely related--just as chimps and humans are. But the closest relative to human pubic lice is not found in chimps, but rather gorillas, which are more distant kin from humans. Reed wanted to know why.

He and his colleagues compared the DNA sequences from two genes in various lice and calculated when the different species appeared. As expected, human and chimp Pediculus (head lice) began to diverge about the same time as hominids and chimps started down independent evolutionary paths, about 6 million years ago. The gorilla and pubic lice (both Pthirus species) split just 3.5 million years ago, however, about 4 million years after gorillas and the line that led to chimps and hominids diverged. Thus rather than co-evolving with our ancestors from the very beginning, these lice were acquired at a later point in time, Reed and his colleagues report today in BMC Biology.

Because lice rarely survive more than a few hours off their hosts, this jump required close contact between the two species. "They must have been in the same place at the same time," Reed points out. Vincent Smith, a cybertaxonomist at the Natural History Museum in London, says the study "raises some interesting questions about what gorillas and our hominid ancestors were doing in such close proximity to share each other's lice.

Here is how you beat indestructible head lice

Head lice don’t pose a particularly serious threat to our health but they do cause great anxiety among parents and carers. This anxiety, and associated stress, is made even worse given the perceived social stigma of a family infested with parasites, and the seemingly endless battle to exterminate these pests.

What are head lice?

Head lice are small insects that are highly adapted to one type of environment: hair on a human’s head (especially the hair and head of primary school-aged children).

Infestation with head lice is affectionately known as “pediculosis”, but while the lice will scuttle up and down the strands of hair, feeding on blood at the scalp, they don’t seem to cause anything other than very mild irritation. They’re not involved in the spread of any nasty diseases either.

But head lice are highly contagious. If you or someone in your family has them, you’ll probably want to get rid of them.

Are head lice becoming ‘indestructible’?

For many years we’ve known that commonly used insecticides (particularly pyrethrins and pyrethroids) aren’t working as well as they once did against head lice. Similar types of insecticides are currently being employed to battle outbreaks of mosquito-borne Zika virus in South America.

In much the same way that mosquitoes, bed bugs and many agricultural insect pests are becoming resistant to commonly used insecticides, so are head lice.

A recent study published in the Journal of Medical Entomology provides some insight into just how prevalent insecticide resistance in head lice may be.

Thanks to school nurses and “professional lice combers”, scientists from the University of Massachusetts were able to analyze more than 14,000 head lice from almost 140 locations across 48 US states. They were looking for the genetic markers that indicate potential resistance to insecticides such as pyrethrins or pyrethroids.

The researchers found a very high prevalence of “knockdown resistance”, a mutation in the insect that make it less susceptible to insecticides. The results suggest that more than 98% of head lice analyzed may not be susceptible to many head lice treatment products currently available.

The result isn’t surprising. With so much use of insecticides against head lice, the development of resistance should almost be expected.

Before everyone panics, it is important to note that while the mutations that confer insecticide resistance were found to be widespread, that doesn’t necessarily mean that all head lice will be resistant to commonly used insecticides. They may be, but we just don’t know to what extent.

There are also likely to be differences between head louse populations across the world.

We can even ditch the insecticides

Here is the really good news. We don’t have to rely on insecticides to control head lice.

The “conditioner and comb” method works well enough. By applying conditioner to the hair, any adult lice present will be “paralyzed” and can then be removed with specially designed “lice combs”. (Interestingly, the earliest known “lice combs” date back to 1500 BC).

Repeat the process a week later to catch any lice that hatch from eggs remaining in the hair and you should be done – at least until next time.

The biggest barrier to success is getting the children to sit still long enough to methodically work through their hair. Wrangling the kids is probably more difficult than wrangling the lice!

Head Lice Prevention: Everything Parents Should Know

Is there a head lice infestation in your child’s school? Learn how to prevent lice with these easy, natural methods.

Head lice have become an increasingly prevalent problem in our nation's schools and child-care centers, according to the American Head LiceInformation Center. Some 12 million people are infected with lice each year, most of them between the ages of 3 and 12. And although head lice isn’t a serious medical problem, it proves annoying for parents, teachers, and students alike. Here are some head lice prevention techniques to stave off a pesky infestation.

Head Lice Prevention: How to Prevent Lice

If you’ve discovered a lice infestation in your child’s daycare or classroom, here are some head lice prevention methods to implement into your daily life.

1. Don’t Touch Heads: Lice are spread most easily by direct person-to-person contact. This is often the case when children touch their heads together during play. Talk to your kid about the risk of lice, and warn him not to come into contact with another child’s head.

2. Keep Belongings To Yourself: Lice also can be spread indirectly when kids share combs or brushes, pillows, or head gear such as hats or helmets. Tell your kid not to borrow these items from others, and separate personal belongings as much as possible in the classroom.

3. Sanitize Your Possessions: Head lice can't survive away from a human scalp for more than 48 hours or at temperatures above 120 degrees. You can use these weaknesses against them when cleaning your house and possessions. For instance, soak all hairbrushes, combs, and hair ornaments that might’ve been exposed to lice in hot (not boiling) water. Wash all stuffed animals, bed linens, towels, and recently worn clothing in hot water, and place them in the dryer on a high-heat setting. Items that can't be washed or dried in this manner can be dry-cleaned or stored in sealed plastic bags for several days.

4. Wash Your Hair with Anti-Lice Shampoo: Anti-lice shampoos claim to fend away infestations, since lice are repelled by their scent. Many of these shampoos contain essential oils; popular options are lavender oil, tea tree oil, and coconut. You can find these anti-lice shampoos at many natural stores; alternatively, consider making your own by mixing small amount of essential oils into your existing shampoo.

5. Do Your Research: Spotting a lice infestation early can save your family from the annoying bugs. Perform routine head checks on your children to search for the tiny mites, which are found most often in the hair above the ears and at the back of the head, just above the neck. More visible though, are the tiny white nits that are found on the hair shaft, just above the scalp. They look like dandruff, but aren't flaky and are difficult to remove. If you are uncertain of what you're searching for, ask your child's school nurse or your pediatrician to show you what a nit looks like.

6. Watch Out for Yourself, Too! Because parents aren't likely to share hats, combs, clothing, and other items – or to come into direct head-to-head contact –  they're unlikely to become infected with lice. "We don't see parents with lice very often, and only occasionally will we even see siblings with it," says Dr. Herbert. Still, if your child does become infected with lice, it's a good idea to have another adult inspect your head just to make sure they haven't taken up residence.

Let's Talk About...LICE

The best part of my day was (and always is) picking JD up from school. But not today. Today, his teacher handed me a paper that read: “Unfortunately we have confirmed cases of head lice within the school. You child’s classroom has been affected. Head lice is highly contagious and we need your help to diligently check your child’s head everyday for the next few weeks.”

My face went white. I felt that woozy panic feeling (I have panic disorder and sometimes I have panic attacks – it sucks!) I didn’t have a panic attack right there, but I did start drilling JD’s teacher. She told me 2 kids were sent home with lice and are not permitted back until they are re-inspected by the school. She told me she checked JD’s hair and scalp and didn’t see anything, but lice are small, like tiny small and clear and JD has white blond hair—awesome. 

My face went white. I felt that woozy panic feeling (I have panic disorder and sometimes I have panic attacks – it sucks!) I didn’t have a panic attack right there, but I did start drilling JD’s teacher. She told me 2 kids were sent home with lice and are not permitted back until they are re-inspected by the school. She told me she checked JD’s hair and scalp and didn’t see anything, but lice are small, like tiny small and clear and JD has white blond hair—awesome. Then she recommended I buy lice shampoo and use it this evening, because if there is lice in his head, it’s good to attack it now before it gets out of control. Now I felt panicky. JD was tugging on my shirt and asking for juice and my head was itching. No time to panic.

I warmed up leftover cavatelli and peas and made chicken nuggets (all white meat - no preservatives!). JD ate and I scanned his head over and over and saw nothing—even with my glasses on. After a successful week of showers, JD was thrilled to take a bubble bath, because the shampoo needed to sit for 10 minutes on his hair. He played happily. "Don't touch your head," I said. "Why?" he asked. "Don't, dude." I Facebook messaged my mom friend, *Valentina who has a daughter in JD’s class. “I did a spot check -- all clear, bathed her and changed the sheets!” she wrote. Sh*t, the sheets! After JD’s bath, I stripped our beds and threw them in the wash with extra soap and hot water. I combed JD’s wet hair strand, by strand and saw nothing, nada. And then I called his Pediatrician and left a message with the answering service because I am THAT MOM. I prefaced my message for the doc to the answering service lady: "Please don't think I'm crazy, but..."

The Dr. was so kind and understanding—and reassuring. She told me if I didn’t see live lice there was no need to use the shampoo. She also said lice don’t leave bite marks, so I shouldn’t freak if I see anything suspect, like a scratch or red spot. She said JD is allowed to itch his head without having lice. She also said The American Academy of Pediatrics recently released a study that said kids with lice shouldn’t have to leave school if they have lice. Lice are not dangerous. They don't carry disease. Our society associates lice with filth and that is false. JD gets one or sometimes 2 baths/showers a day. His school is clean and bright—one of the best in our area—and lice happens. But I HOPE it doesn’t happen to us. I’ll be checking 24/7. I’ll be checking my thick, super-long hair too. Great.

Don't Bug Out, but Most OTC Lice Treatments Don't Really Work Anymore

Overuse of common lice treatments have rendered them ineffective, according to a new study.

Ugh, lice. Those little creepy-crawlers can do more to ruin your week than a stomach bug. You see one louse, and the next thing you know, your house looks like the scene from E.T. when the men in the moon suits move in.

As if treating lice isn't fun enough, and with lice likely to spread now that school is in full swing, a new study in the journal Pediatric Dermatology notes a marked decline in the effectiveness of one of the most common forms of OTC treatments.

Specifically, permethrin or synergized pyrethrins (also known as pyrethroids), which are listed as the active ingredients on the popular anti-lice product I used in the past during an outbreak in our home, don't work as well as they used to, likely due to overuse.

The study also noted the potential toxicity of lindane, and advised against using products that contain it. Researchers instead recommend that parents use prescription products deemed safe and effective, including those that contain malathion, benzyl alcohol, spinosad, and topical ivermectin.

"The lesson we should learn is that those products that do remain effective, which are available by prescription, should be used judiciously so that they do not suffer the fate that has befallen the pyrethroids," lead author Dr. Ellen Koch said in a press release.

Study authors further noted that use of home remedies like petroleum jelly, mayonnaise, and essential oils are not advisable, as they have not been shown to be effective, and may even lead to adverse reactions.

The bottom line: It seems when you detect lice in your home, a phone call to the doctor is in order. Otherwise, you could end up wasting time and money (and sanity) trying to rid your kiddos of, let's face it, the biggest little pests ever.

New Lice Recommendation Has Parents Scratching Their Heads

In a surprising recommendation, pediatricians say kids with lice shouldn't stay home from school, and they explain the best treatment and prevention methods.

The Short of It

It's enough to freak any parent out: Someone in your kid's classroom has head lice. Many of us have had notes sent home telling us to look for signs of the little parasites and to keep our child home if they have them. But, the notes home may end. And in fact, according to a new recommendation, kids with these creepy crawlers should be welcomed in school with everyone else.

The Lowdown

The American Academy of Pediatrics (AAP) announced its new policy, which may raise some parents' eyebrows, Monday.

"Most cases of head lice are acquired outside of school," says the announcement. "The AAP continues to recommend that a healthy child should not be restricted from attending school because of head lice or nits (eggs). Pediatricians are encouraged to educate schools and communities that no-nit policies are unjust and should be abandoned. Children can finish the school day, be treated and return to school."

The recommendation is based on a clinical report published in the "Journal of Pediatrics," which found that only a third of kids with five or more nits actually developed an active infestation. Taking those kids out of school would have been unnecessary.

"In addition, head lice infestations have been shown to have low contagion in classrooms," says the report. (The report also said the bugs don't hop or jump—who spread that nasty rumor?)

Researchers found that the best way to treat nits is to use an over-the-counter treatment containing 1 percent permethrin or pyrethrins. If there's a chronic lice problem, use an OTC pediculicide and follow the manufacturer's instructions. Then reapply it at Day 9, and if necessary, at Day 18. If that doesn't work, your child should see a pediatrician.

The Upshot

This busts a big lice myth we've all come to believe: That your child is mostly likely to contract—or spread—lice while at school. And while this might worry some parents (anyone who's been through an infestation knows it isn't pretty), it may be a relief to not have to take days off work or have their child miss valuable school lessons when a few nits are found.

Head lice can't be completely prevented, but you can lower your child's risk by teaching them to never share combs, brushes or hats. Check your child regularly for signs of nits, and if one family member gets them, everyone in the household should be checked. Anyone with nits or an active infestation should be treated right away.