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.”

I Spent Years Dreading the Day My Daughter Would Get Lice — and Then It Happened

I had just escaped from my kids, handing them off to my husband to take a few minutes to myself before the chaos of bath and bedtime began. The calm didn't last long. Five minutes later, he entered our bedroom and announced that our daughter had lice. "Are you sure?" I responded, hoping, of course, that the answer was no. "Look for yourself," he replied instead. I did, and yep, that definitely wasn't a case of dandruff. Those were bugs crawling around on my daughter's head.

Her lice took me by surprise (though is anyone really expecting it?). Months before, when I got notes home from school about the cases reported in her classroom, or when her best friend's mom called to let me know her daughter and son, who had been in my carpool just that afternoon, were both lice-infected, I had braced myself for an impending doom that never came. I heard horror stories from my neighbor, mom to one of my daughter's classmates, about her whole family battling lice. At one point, she said, she was seriously considering shaving her own head just to ensure she'd gotten them all. 

My own scalp immediately began itching, though my husband couldn't spot a single nit (weeks later, that phantom itching still happens every time I even think about the word "lice"), and I began picturing the long, complicated, and annoying process that ridding our family and home of lice would entail. I'm glad to say that although it was pretty annoying (never have my washer and dryer worked harder), we were able to defeat the lice — it ended up only affecting my daughter, who luckily had a mild case — within 24 hours. Here are six things I learned about lice and getting rid of it that I never knew. If your house comes down with a case, don't despair. You can vanquish those annoying bugs quickly and thoroughly. 

Related:

My Toddler's Eardrum Ruptured and I Didn't Even Know It

• Lice are only passed through head-to-head contact. Head lice don't crawl, jump, or fly. The main way they spread is from close, prolonged head-to-head contact, and to a lesser degree, they spread through items that come into contact with an infected head, like brushes, hats, and (at our school found out last year) the helmets used in gym class. 

• You'll almost certainly know them when you or your child gets them. When friends and classmates of my daughter's got lice, I checked her head obsessively, wondering if I was missing something. I wasn't. She was clear. When she actually did have lice, she complained about her head itching, and when we checked, it was pretty easy to spot a few bugs (they're called a louse, are around two millimeters long, and are pale gray in color) crawling around on that head of hers. Because she's blond, the nits (tiny white or yellow eggs that attach to the hair with a sticky substance that holds them firmly in place) were harder to spot, but because of the bugs, we knew they were there.

• Lice don't live long off a head. Head lice only live with the aid of a scalp to feed on (gross, I know). Once they leave a head, they're usually dead in a day, two tops, so don't feel like you have to fumigate your whole house. Instead, focus on the things that have come in contact with your child's head over the past 48 hours (beds, brushes, hats and hair bands, towels, and clothing are the big ones).

• A laundry cycle will kill lice. Wash all bedding and clothing that's come in contact with the a louse-infested person in very hot water, then put it in the hot cycle of the dryer for at least 20 minutes, and you're golden. I continued to wash my daughter's pillowcases every morning for a few more days just to be safe.

• Isolate or clean items that can't be washed. You can put items like stuffed animals in a bag or simply isolate them from your child and you can be assured that they'll be lice free in a few days. Simply vacuum rugs, carpets, upholstered furniture, and your car. Hair items like brushes, hair ties, and headbands, you can either wash in hot water, soak in rubbing alcohol for an hour, or simply toss. 

• Don't be afraid to call in the professionals. When I texted my neighbor who was threatening to go bald the previous year because of lice, she directed me to a nearby "salon" that focuses solely on removing lice. While the service wasn't cheap (because of my daughter's mild case, we opted for the shorter comb out, which was still around $150). However, they were able to remove almost the 55 nits that were still inhabiting my daughter's head after we used special lice shampoo and spent three hours combing out her hair the night before. We also bought a far superior comb than the one that came with the drugstore lice shampoo we'd used. After that one service, the lice were gone, so in my mind, it was definitely money well spent. We followed their comb-out advice and kept checking for the next few weeks, but thankfully, not a nit was found.

De-lousing the house

Parents frequently ask us at Larger Than Lice how to remove head lice within the home. If I can only count how many times I, or one of our Lice Specialists have arrived to a home only to find ten, twenty, thirty garbage bags full of “household things”. One family even went as far as removing their curtains, just in case. On top of all that, countless numbers of laundry loads have already been done. No wonder head lice becomes such a stressful event for many parents. I almost feel bad telling the families that all this cleaning is just excessive and not necessary at all. That’s right. Excessive cleaning is not at all required when you, or your child has a case of lice.

The reason? Head lice live on the head. They do not live on inanimate objects. They have no interest in leaving one’s head to go wander around on the living room couch, or kitchen floor, or roam the car. A human host is the only place they want to be, the only place that they can potentially survive a whole month while they feed off of the blood of an individual. Typically, a louse that has fallen off the head is not healthy and is in the process of dying. Once they are away from their feeding source, a louse can only survive up to 24 hours. And let's pretend as though a healthy louse has fallen off and has found its way onto the couch- it will not burrow or sit around and wait for another human to sweep it off its feet and place it back into a new head. The chances of getting a displaced louse back into one’s hair are as small as finding a needle in a haystack, nearly impossible.

• Remember that lice are not living in your environment, they are living with you!

Don’t get me wrong, there are some things that need to be cleaned and laundered, but the list is very minimal. Laundering the bedding, any recently used towels and bathrobes is important. Same goes for all recently used hairbrushes and hair accessories. Bagging, laundering or drying on high heat should be considered for any stuffed toys that reside in your child’s bed. That is it. Use the rest of your energy on properly eliminating head lice and nit picking. Being meticulous is essential if you want to rid head lice for good. Removing every single nit is crucial to being lice free so make sure that no nits are left behind, which is exactly what Larger Than Lice are experts in.

When Larger Than Lice dispatches a Lice Specialist for an in-home lice removal treatment, you can rest assured that every single live louse and viable nit will be removed – in just one visit. After one lice treatment, and minimal laundering, you can rest at ease and be confident that your home will be lice-free.  

How Do We Get Head Lice?

In most cases head lice are transmitted from one human to another, primarily through head-to-head contact. While most references report them as most commonly found on children ranging from ages three to eleven, never research shows the largest number of cases are found in children between the ages of nine and sixteen. 

• Head-to-head contact is the most common way to transmit head lice.

While it is possible to pick up hitchhikers (an abandoned strand of hair with a louse still attached), it is suspected that less than 2% of all active cases are actually contracted in this manner.

Lice eggs, or nits as they are commonly referred to, also are of little concern as they cannot reattach themselves to a new head of hair. Furthermore, it should be noted that majority of abandoned nits are damaged and never reach the stage of hatching, thus reducing the chances of exposure through this means. Even if they do manage to hatch, they require blood almost immediately or will starve to death.

• A nit "louse egg" is attached to the hair shaft with a fixative glue. It is a cement-like substance will not dissolve and prevents nits from falling off the hair.   

An adult louse rarely leaves the security of a warm, generous host unless it has already identified a newer and more desirable environment to move onto. Since head lice feed every three to four hours they are unlikely to willingly leave their food supply. It´s also worth noting that lice prefer round shafts of hair because it´s easier to wrap their claw like feet around it.

• The hair of African-Americans is generally oval, a shapeless maneuverable and thus less desirable to the louse.

Lice are also found curly hair less appealing. It´s important to remember that although the shape of certain hair shafts reduces the risk of getting head lice, it does not make the person immune. With an increased number of interracial children, hair textures are changing, resulting in more cases of head lice among select racial groups than previously experienced.

• Lice are more commonly found on girls than boys, presumably because their mass and longer length offer more secure and attractive breeding ground.   

Additionally, girls tend to be more physically affectionate than boys, resulting in more head-to-head contact. Longer hair, often found in girls, becomes a bridge of opportunity, offering a mode of transportation from one head to another. The risk is increased if the child´s hair is loose. The smaller volume of hair on most boys allows for more sun exposure, causing the sink to have a tougher texture and thus be a less inviting feeding ground for lice. Since head lice are lazy, they tend to look for a head that requires less work to obtain their needed food supply. I can't emphasize enough that while these reasons allow for more cases of head lice to be found on the gender and among certain races than others, it's no guarantee individuals in the less likely groups will be immune from them.

• How can we prevent lice? By checking your child's head every week, you will help prevent lice infestation in your home. Head lice will survive for only 24-48 hours once they are not on the host (head).

What Are Crabs (Pubic Lice)?

"Crabs" is the common term for lice found in the pubic hair of humans. Crabs is a parasite infection medically known as Pediculosis pubis or pubic lice. Barely the size of a pinhead, lice are organisms that live only with the help of another organism, called a host. There are thousands of types of lice, some of which have developed an attraction to humans. The official name for the organism responsible for pubic lice is Pthirus pubis. Other lice that often infect humans are Pediculus humanus capitis (head lice) and Pediculus humanus corporis (body lice). The term "crabs" seems to come from the microscopic appearance of the pubic louse. The pubic lice organisms are visible to the naked eye in affected areas. The lice are typically seen attached to hair in pubic areas, but may sometimes appear in other areas of the body where coarse hair is present (such as beard, chest, armpits, etc.).

The pubic louse is distinct morphologically (somewhat rounded with three pairs of legs on either side of the body from which it takes its descriptive name) from the head and body louse. The female lifespan is slightly shorter (three weeks), and she produces fewer eggs per day (three) than her counterparts. The eggs attach to the base of the pubic hair shaft for approximately six to eight days before hatching.

A new case study in The New England Journal of Medicine tells a torrid tale of an unnamed 65-year-old man who showed up at a dermatology clinic complaining of an itchy crotch. On examination, the man didn’t appear to have a rash or any lesions, so the doctors investigated his pubic area with a hand-held dermoscope.

The first bit of evidence they uncovered was a nit firmly implanted on a pubic hair. And then came the culprit itself—a freakishly agile, crab-shaped parasite moving from hair to hair like it was nobody’s business.

For the dermatologists, it was a classic case of pubic pediculosis—also known as “crabs.” This happens when the pubic louse, Pthirus pubis, infests a person’s hairy nether regions.

“Pubic pediculosis is usually sexually transmitted but can occur after contact with fomites [materials that are likely to carry infection] such as clothing, bedding, and towels used by an infected person,” write the researchers, who work out of Mexico City’s General Hospital. “The condition most commonly affects teenagers and young adults. This patient reported that he had had no recent sexual contact, and no other sexually transmitted infections were identified on screening.”

The doctors prescribed the oral drug ivermectin, and after two weeks the itching was gone. Which is all fine and well—but what about the psychological scars?

Three things you probably didn't know about crab lice.

Crab lice (Pthirus pubis) aren’t crabs at all—they’re parasitic insects that feed exclusively on human blood, and their bites can cause intense itching in their hosts. Often, this itching happens in the pubic area, which is why they’re also known as “pubic lice”—which, it turns out, is actually a misnomer.

• They’re not just spread by sexual intercourse.

Although sexual relations are the most common way to pick up these particular passengers, any prolonged close physical contact can do the trick, including breastfeeding or sleeping in the same bed as an infested individual. A few reports have suggested that crab lice can tolerate being away from a human host for as long as 36 hours, which opens up the possibility that the lice could hang out on previously used towels and sheets to wait for a new host.

• Their closest cousins live on gorillas.

Studies comparing DNA from the three species of human louse with the lice that infest other primates found that the crab louse’s closest relative is the gorilla louse. Head lice and body lice belong to a completely different genus of lice and are more closely related to the lice that live on chimpanzees. But researchers don’t think that humans picked up crabs from screwing gorillas. It’s much more likely that we got them by eating gorillas. Lice are very sensitive to body heat, and it’s possible that way back in the distant past, some gorilla lice abandoned a cooling dead host for the warm human that was butchering it.

• They don’t just live in pubic hair.

Crab lice certainly prefer the pubes, but their short, thick legs are just as well adapted to hang on to any coarse hair on the human body. They’ve been found in armpit hair, beards and mustaches, eyelashes, and eyebrows. They’re not big fans of densely packed hair, so they’re rarely found on the scalp. But if your scalp hair is sparser than average, as in people with curly locks, they might make an exception. Take home message? If you have a head louse infection, you only need to treat your scalp. A crab louse infection means all bets are off. Treat all of your hair. All of it.