If you have young children heading back to school this fall, you'll want to know about head lice: what they are, how to protect against them, and what to do if and when they land in your child's hair. 

Lice are sesame-seed-sized, wingless insects that feed on human blood. They don’t transmit disease, but their bites cause intense itching, which can lead to sores and possible secondary infections.

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Super lice 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 most over-the-counter lice shampoos.

Some studies suggest that two-thirds to three-fourths of all lice are now super lice. One recent study found that the proportion might be even higher: 95 percent of the lice collected from 48 states were super lice.

That means that if your child gets head lice—roughly 8 million cases are reported in the U.S. each year—you’ll need more than a quick trip to the drugstore. 

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 infection (or 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. 

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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. 

Avoid These Products

Shampoo shields: These products claim they can prevent or reduce the risk of getting head lice, but evidence is sparse. The Federal Trade Commission charged the manufacturer of at least one such product with false advertising.

Over-the-counter lice killers: As noted, over-the-counter products that contain pyrethrins or pyrethroids (like permethrin) are unlikely to offer much relief because many to most lice are now resistant to those chemicals. In fact, they could prolong a person’s suffering, because it takes a few days to know whether the product is working.

Household fumigants: These chemicals can be toxic if inhaled, and they pose an explosion risk near a heat source. They are also 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. 

Pricey prescriptions: Skip products containing lindane. This chemical is neurotoxic and carcinogenic to humans, and has been linked to reports of seizures and even deaths from improper use.

The Food and Drug Administration has approved several additional lice-killing prescriptions in the past decade. One, Ulesfia, contains high levels of alcohol and works by suffocating the lice. Another, Natroba, contains a chemical derived from bacteria that acts on the lice’s nervous systems (they become overexcited, then paralyzed, then die). A third, Sklice, contains ivermectin, which is also bacteria-derived and acts on the lice's nervous systems (ivermectin is a common veterinary medicine, too).

These newer prescriptions may well work against super lice because they act via different mechanisms than the pyrethrins or pyrethroids. But you'll need to go to the doctor, and these products are expensive—$100 or more for a single treatment. What's more, they won’t necessarily kill the lice eggs. And because young children have thinner skin, they are more susceptible to absorbing these chemicals through the scalp and to the side effects that they might cause.

Home remedies: Some alternative treatments—like butter, oil, and petroleum jelly—rely on suffocating or drowning lice, but a 2018 study suggests that this strategy might not work. Researchers found that 100 percent of tested lice survived 8 hours without oxygen, and 6 hours immersed in water. Many were able to survive under those conditions for much longer.

Try a Simpler Approach Instead

Our experts say that the best approach is also the easiest: using a wet comb.

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, concentrating on the area close to the scalp. After each comb-through, wipe the comb on a paper tower 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.