Lice are resistant to many of the products used against them, but there are ways to win this battle of bugs
By Catherine Roberts
Between 6 and 12 million children ages 3 through 11 get head lice every year in the U.S., according to an estimate from the Centers for Disease Control and Prevention. That’s a lot of itching. If you’re trying to figure out how to make it stop, you have a lot of options—but some are better (and safer) than others.
First, it helps to know the basics: Head lice are sesame-seed-sized, wingless insects that feed on human blood. "As far as we know, [they] do not transmit any human disease," says L. Paul Guillebeau, PhD, professor of entomology at the University of Georgia.
That means their presence on your child’s head doesn’t constitute a medical emergency. Still, lice are distressing, and their bites cause intense itching, which can lead to sores and possible secondary infections.
The rise of "super lice," meanwhile, has made treating a head lice infestation harder than it once was. These pests are just like regular lice except that they’ve acquired genetic mutations that make them resistant to plant-derived insecticides called pyrethrins and their synthetic cousins, pyrethroids. These are the active ingredients in many over-the-counter lice treatment shampoos. Research suggests that today, super lice are virtually ubiquitous, says Michael Hansen, PhD, CR’s senior scientist.
Here, we explain how to protect your family from lice, plus what treatments you should turn to if a family member picks up lice.
Protect Your Family
Lice can crawl from one head to another in seconds—for instance, when children touch their heads together during play or when they share a comb or a hat.
If a friend, a relative, or your child’s school reports a head lice infestation, inspect your child right away. A single female louse can lay up to six tiny, pearl-colored eggs, or nits, a day. They lay the eggs near the base of a hair shaft, especially behind the ears or on the back of the neck. A child’s first-ever infection might not be detected for a month, because that’s how long it takes to develop a sensitivity to the lice saliva, which is what causes the itching. During that first month, you might mistake a lice infection for dandruff or eczema—but a lice infestation doesn’t go away after shampooing.
If your child has head lice, all household members should be checked and treated, if necessary. You don’t need to go crazy with the housecleaning because head lice won’t survive long if they fall off a person and can’t feed. To prevent reinfestation, concentrate on cleaning the things that your child’s head came into direct contact with in the past few days.
Wash or dry clothing and bed linens at temperatures above 130° F. This will kill stray lice and nits. Seal clothing or other items that are not washable in a plastic bag for two weeks, or put them in the dryer. Soak combs and brushes in very hot water for 5 to 10 minutes.
Remind your children not to share combs, hair ornaments, or hats, and ask them to stuff their jackets into their backpacks at school, rather than hang them on a communal hook.
The Lowdown on Lice Treatment Products
To provide advice on lice treatments, members of CR’s product safety team and our senior scientist, Michael Hansen, PhD, did a thorough review of existing evidence about lice treatments in 2019. As we’ve done for several years, we recommend combing out lice from wet hair, without the use of any pesticide products, as a top choice for parents. Here, we offer more advice on how to perform combing, plus important information about a number of other available treatments.
If you do opt for a lice-fighting product, be sure to follow the directions carefully, and pay attention to whether or not a follow-up treatment is recommended. Because many products don’t kill nits (lice eggs), an additional treatment a few days later may be necessary to get rid of any newly hatched lice. Some products may also recommend combining treatment with combing.
And remember that even the most effective methods of tackling a lice infestation aren’t guaranteed—you may need to try more than one strategy.
Wet combing involves carefully combing with a nit comb to physically pick out nits and lice.
What to know: Our experts say that wet combing is a great approach to treating head lice for many people. It can be time consuming and requires perseverance, but no pesticides or pricey products are involved. Here’s how to do it:
Coat your child’s hair and scalp with conditioner or a safe lubricant such as olive oil. Use a wide-tooth comb to separate hair into sections. Follow with a metal nit or flea comb, available at drug or pet stores, concentrating on the area close to the scalp. After each comb-through, wipe the comb on a paper towel and inspect for lice. Continue combing until no lice are found; a single session can take 15 to 60 minutes, depending on the length and thickness of hair.
Repeat every three to four days for several weeks, and continue regular combings for two weeks after any session where an adult louse is found.
Some people may also opt to hire a professional nit picker or "lice lady" to do the combing for them in the case of a lice infestation, though of course that’s costlier than doing it yourself. Combing also has some drawbacks, particularly for people with curly or Afro-textured hair. According to a 2023 paper in the Journal of the American Pharmacists Association, frequent use of nit combs on curlier hair types is likely to lead to breakage, since curlier hair is more fragile than straighter hair. Parents of children with curlier hair may want to consider some of the other effective treatments, discussed below.
One common lice product is preventive shampoo, sold under brand names like Lice Shield or Hair Genies. These products claim they can prevent or reduce the risk of getting head lice.
What to know: These products aren’t labeled as treatments for an active lice infestation. We couldn’t find any evidence that suggests these products can treat an existing infestation.
And even as preventives, these products may not be a great bet. In 2014, the Federal Trade Commission charged the manufacturer of one such product, Lice Shield, with false advertising for claiming that its product reduced the likelihood of a lice infestation. (The company, Lornamead, settled the complaint by paying $500,000 and was "prohibited from making further deceptive lice-prevention claims," according to the FTC. The company did not respond to a request for comment in 2019 and did not immediately respond to a 2023 request for comment.)
Using one of these preventive shampoos is likely to be a waste of money, says Jody Gangloff-Kaufmann, PhD, coordinator of community integrated pest management (IPM) at the New York State IPM Program. She doesn’t know of any substances that have been shown to repel lice effectively. "Lice are more compelled to eat than they are repelled by any smell," she says.
Over-the-counter products that contain pyrethrins or pyrethroids (like permethrin) are still considered the first-line treatment by the American Academy of Pediatrics. But CR’s Michael Hansen cautions that they’re unlikely to offer much relief because many to most lice are now resistant to those chemicals. In one 2016 study published in the Journal of Medical Entomology, researchers collected lice from 138 different sites in 48 states. They found that 98 percent of those lice had genetic mutations that would make them resistant to permethrin and pyrethrin, the active ingredients in Nix and Rid.
What to know: The scientific evidence on pesticide resistance suggests that these products are unlikely to be effective. Our experts recommend skipping them. "These products can cause side effects, like burning or skin irritation," Hansen says. "Given that they’re highly unlikely to do any good, they’re just not worth the risk."
In fact, they could prolong a person’s suffering, because it takes a few days to know whether the product is working. If you do try one of these products and it fails, switch to another method. It can be dangerous to do the same pesticide treatments over and over, says Gangloff-Kaufmann.
Household Pesticide Products
You may think that pesticide fogs or "bug bombs" could be used to control a lice infestation in the home. But these chemicals can be toxic if inhaled, and they pose an explosion risk near a heat source.
What to know: The CDC recommends against these, and so do CR’s experts. They are unnecessary. As noted, lice can’t live for very long away from actual human heads, where they draw their blood meals. So most lice around the house will die anyway.
Other Pesticide Treatments
A variety of other pesticide treatments are available for head lice. The Food and Drug Administration has approved several of these in the past decade. One, topical spinosad (Natroba and generic), contains a chemical derived from bacteria that acts on the lice’s nervous systems (they become overexcited, then paralyzed, then die). Another, topical ivermectin (Sklice), works similarly (ivermectin is a common veterinary medicine, too) and recently became available for purchase over-the-counter rather than by prescription.
Two older prescription medications, malathion (Ovide and generic) and lindane (Scabene, Kwell, and generic) are also available.
What to know: According to clinical trials of the drugs, spinosad and ivermectin appear to work relatively well against lice. They act via different mechanisms than the pyrethrins or pyrethroids, so they should work even against lice that are resistant to those chemicals—at least for now.
Like pyrethroid treatments though, they also have potential side effects, such as skin or eye irritation, burning, and dryness.
Skip products containing lindane and malathion, our experts say. Lindane is neurotoxic and carcinogenic to humans, and it has been linked to reports of seizures and even deaths from improper use. Malathion hasn’t been proven safe on children under 6 years. It’s also highly flammable and in some cases can cause stinging and chemical burns.
Non-Pesticide At-Home Treatments
To address the problem of pesticide resistance in super lice, some companies have introduced products that claim to get rid of lice without pesticides. You also might have heard of home remedies for getting rid of lice, such as the application of mayonnaise, oil, or petroleum jelly.
A number of these non-pesticide treatments, both home remedies and consumer products, rely on suffocating or drowning lice. These are sometimes referred to as “occlusive” lice treatments. The emollient ingredient dimethicone, which suffocates lice, is in products such as Nix Ultra and LiceMD.
What to know: These products aren’t pesticides, so lice are unlikely to adapt to become resistant to them. The active ingredients are common in a variety of cosmetics, and they’re unlikely to pose major risks.
Evidence on their efficacy varies. Dimethicone in particular is popular as a lice treatment in Europe, and several studies show it is effective. (Note that dimethicone treatments are generally paired with combing.)
One 2020 analysis of existing studies pooled data from clinical trials comparing occlusive lice treatments to pesticide-based treatments. The included trials tested synthetic occlusives such as dimethicone, as well as home remedies like petroleum jelly and paraffin. It found that the occlusive treatments performed at least as well as pesticide-based treatments, though the researchers characterized that result as “low certainty” overall and noted several limitations.
When considering home remedies alone, the evidence is slim. And a 2018 study that looked exclusively at home remedies including petroleum jelly, mayonnaise, and olive oil, found that none were particularly effective.
Plus, Gangloff-Kaufmann says that these types of home treatments are often left on hair overnight, covered with a shower cap or plastic bag to keep the mayo or oil from getting everywhere. This can pose a choking hazard, she notes.
Hot Air Treatment
At the lice treatment chain Lice Clinics of America, you can receive treatment with a hot air device called the AirAllé. The company guarantees elimination of nits and lice in one treatment.
What to know: We couldn’t find much evidence of the treatment’s effectiveness beyond the studies that the device’s inventors have published. Those studies do show promising results. Still, the treatment can be pricey—it varies by location, but the price appears to run generally between $150 and $200.
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