What Is Head Lice? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Head lice are tiny, wingless parasitic insects that reside on the scalp, where the temperature is warm, consistent, and very hospitable. Sometimes you can find head lice (Pediculus humanus capitis) on eyebrows, eyelashes, and neck hair as well. One place you will not find head lice? On dogs, cats, or any other animal. Head lice is a 100 percent human issue. And since head lice survive and thrive solely on human blood, once they’re separated from their human host, they starve and perish within several hours. Nits (head lice eggs), on the other hand, generally die within a week away from their human host. While it’s true that an infestation of head lice is inconvenient and perhaps uncomfortable, it’s usually harmless, notes the Centers for Disease Control and Prevention (CDC). (1)

Not all people with head lice exhibit the very same lice symptoms. But the most common signs that you might be dealing with a head lice infestation include:

Itchiness This may be felt on the scalp, neck, or ears. Itching is often a sign of an allergic reaction to louse saliva or feces. (2) (Of note: For folks dealing with their first infestation, itching may not occur until two to six weeks after the outbreak begins.)

Trouble Sleeping Lice are more active in the dark, so those with an infestation may experience issues falling asleep thanks to this uptick in movement. (2)

Red Bumps or Sores For some, the infestation may go hand-in-hand with a rash, which can lead to excessive scratching. This can lead to a bacterial infection, complete with swollen lymph glands, tender skin, and oozing sores. If this occurs, your physician may treat the infection with an antibiotic. (3)

Visible Nits While the presence of nits does not always indicate that there’s an active infestation, it can. (2) Look for oval-shaped nits that are about the size of a grain of sand, stuck to the base of the hair shaft, closest to the scalp. At times, nits appear to be the same color as the hair in which they reside, making them very hard to spot. (Empty or hatched nits are lighter in color and further from the scalp and can be easier to see.) When not mimicking the host hair color, nits look yellow or whitish, which is why nits are often confused with dandruff or droplets of hair spray. (1)

Visible Nymphs or Lice Both nymphs (young lice) and mature head lice remain small — the size of a pinhead and the size of a sesame seed, respectively. They can be found on the scalp, around the ears, or at the base of the neck. They’ve got six legs and hook-like claws, and adults are often tan or grayish white. They may appear darker if their host has dark hair, though. (1) They may also appear red if filled with blood. (4)

Contrary to popular belief, head lice cannot fly, jump, or hop, so it’s uncommon for people to spread lice by sharing belongings such as hats, helmets, and hair brushes. And personal hygiene — or lack thereof — has nothing to do with getting head lice. (1) Instead, “direct head-to-head contact is how we transfer lice,” says Richard J. Pollack, PhD, a senior environmental public health officer and researcher at the Harvard School of Public Health in Boston. (This was also confirmed by a study from 2015.) (5) With that, here are the risk factors of head lice:

Young Age Children ages 3 to 11 get head lice most often. Because younger children tend to have more head-to-head interactions — sharing a bed, parent snuggles, wrestling — they have far more opportunity to spread their head lice with one another than older kids and adults. “As such, prevalence drops dramatically once kids get to middle school,” says Dr. Pollack. (The CDC lists attending day care and elementary school as a lice risk factor.) (1)

Proximity If you live with someone who’s dealing with a head lice outbreak, your chances of also becoming infested go up, regardless of age. (If one person is found to have head lice, all household members should be checked for head lice.) (1)

Sex Girls have a 2 to 4 times higher chance of becoming infested by lice than boys. It’s speculated that the reason may be attributed to the fact that girls often have longer hair, according to 2020 study. (6) It’s also thought that, perhaps, this may be because girls experience more frequent head-to-head contact than boys. (7)

Race Black children in the United States have far fewer reported head lice infestations than other ethnic groups, according to a report. (8) It’s thought that this may be due to differences in hair thickness and curl. And that fact that lice most frequently found in the United States have claws that may be better able to grasp the hair shafts of other races. (1)

The best way to zero in on an accurate diagnosis of head lice is to find a live nymph or adult louse on the scalp or hair. When looking, concentrate on the scalp, behind the ears, and around the nape of the neck. (3)

Lice are very small and move quickly, so begin by parting the hair into small sections and using a magnifying glass, as well as a special fine-toothed metal comb called a nit comb. The special lice comb may help you locate live lice more quickly and efficiently than without the comb, according to a study. (9)

“If you find a crawling bug on the scalp hair and it looks consistent with the images of head lice, then your lice conclusion is likely correct,” says Pollack. But if you are unable to find a live, moving louse, proceed with some doubt.

While most schools regularly screen children for lice, it’s important to know that this has not been proven effective at reducing the incidence of head lice in school. (3) “There are a lot of misdiagnoses at school head checks,” says Pollack. “Parents should carefully consider the evidence before starting treatment.” Again, finding a living and crawling bug on scalp hair that matches with the images of head lice is the best evidence.

“What parents and teachers sometimes believe to be nits are often confused with other things found in the hair, such as dandruff, hair spray residue, and dirt,” says Pollack. In fact, according to Pollock’s published research, most of the presumed “lice nits” and “lice” that doctors, nurses, and others have submitted to laboratories for identification were ultimately found not to be lice. (10) One common misdiagnosis is hair casts, or pseudonits — thin, elongated, firm, white attachments to the hair shaft that resemble nits. But unlike nits, they can easily be dislodged. (11)

That noted, nits are coated in a glue-like substance that very strongly attaches to the hair shaft, making it far more difficult to shake a nit loose than other foreign objects. If you discover lice eggs that are firmly attached within ¼ inch of the base of the hair shaft, you may be dealing with an infestation. If the lice eggs are found more than 1 centimeter from the scalp, on the other hand, they’re likely dead or already hatched, indicating an old and inactive infestation that doesn’t require further attention. (5)

If you discover a member of your household has lice, check everyone in the home who had close contact with the infested person every three or four days. (3)

Unsure whether or not you’re dealing with an active lice infestation? Visit a healthcare provider or a person specially trained to identify live head lice. That individual may use a specialized light called a Wood’s lamp, which makes the lice nits appear bluish in color. If suspicious lice eggs are found, they’ll be examined under a microscope to determine if there is, in fact, an active head lice infestation. (12)

When infested, kids usually carry fewer than 20 mature head lice, each of which, if left totally untreated, live for three to four weeks. The kicker, of course, is that those lice mate and produce more eggs, thus more lice. In fact, the adult female louse can produce up to six eggs a day for 30 days, noted research from 2018. (13) With that, duration of an infestation greatly depends on which treatment is used and how effective said treatment is.

It’s only recommended that you proceed with head lice treatment if an active infestation of head lice is confirmed. Meaning: The lice need to be alive and crawling, or the lice eggs need to be viable, to warrant treatment. Still, it may be prudent to go ahead and treat those who share the same bed with an actively infected person. (14)

Medication Options

There are several prescription and nonprescription treatments that effectively kill head lice. The one you choose will depend on what treatments you’ve already tried. While these treatments usually kill lice, it can take up to several days for the itching to subside. (3)

• Nonprescription Lice Shampoo and Cream Every over-the-counter (OTC) treatment of head lice has been approved by the U.S. Food and Drug Administration (FDA) and contains either pyrethrins (Rid or Triple X) or permethrin (Nix). Both are effective and are considered the first line of treatment. The former can be used on children ages 2 and older, while the latter can be used on children as young as 2 months. Both only kill live lice, not nits. (12) After an initial at-home treatment, check hair to see if lice appear less active after 8 to 12 hours. If you don’t notice a difference, refrain from retreating. Instead, check with your doctor to see if another product may be needed. (15) If after that time frame, you do notice a slow down, it’s still recommended that you retreat within seven to nine days in order to kill any lice that have hatched after the first round. Two treatments usually get rid of the lice. (Combining out hair for two to three weeks also helps.) (14)
• Prescription Shampoos and Lotions If an at-home product doesn’t knock out the infestation, talk to your doctor or dermatologist. They can prescribe a stronger lice treatment, like prescription permethrin. Lindane, a prescription lotion or shampoo, is less effective than prescription-strength permethrin and, because of the possible toxic side effects, is not recommended for children younger than 2, pregnant or lactating women, or those with a seizure disorder. While prescription malathion is very effective at killing both head lice and lice eggs, it’s not considered a first-line treatment because it needs to remain on hair for 8 to 12 hours to work. (11) Other prescription options include benzyl alcohol lotion (Ulesfia), ivermectin (Stromectol) lotion, and spinosad topical suspension. (12)
• Oral Prescription Medication When other treatments fail, oral ivermectin may be an option. While it effectively treats a head lice infestation with two doses eight days apart, side effects may include nausea and vomiting. (Children must weigh at least 33 pounds to take this medication.) (12)

Manual Treatment

Medicated lice treatments should not be used on children 2 months or younger. If an infant has an active head lice infestation, you must remove the lice and lice nits by hand with a fine-tooth lice comb, first wetting and conditioning the child’s hair. This needs to be repeated every three to four days for three weeks after the last live louse was spotted. (3)

Alternative and Complementary Therapies

Suffocating Agents There’s strong anecdotal evidence the shows applying Cetaphil, mayonnaise, or olive oil to the hair can suffocate lice, but there’s little scientific evidence proving the same. (12) Instead, there was a study that reported a 96 percent “cure” rate when Cetaphil cleanser was applied to hair, dried on with a blow-dryer, left overnight, and rinsed in the morning and repeated once a week for three weeks. The study was not uncontrolled, nor randomized, though. (16)

Heat A device called AirAllé uses a 30-minute blast of hot air to kill lice. And it has been shown to be an effective method, knocking out nearly all lice eggs and 80 percent of live lice after one treatment. This special machine is only found at professional lice treatment clinics. (17) (A regular blow-dryer does not work in the same way and should not be used as treatment, since blow-dryers can cause lice to become airborne.) (5)

Essential Oils The use of essential oils such tea tree oil or ylang ylang oil have yet to be proven effective and can cause allergic skin reactions. Experts recommend avoiding this treatment method. (3)

Learn More About the Treatment of Head Lice

Prevention of Head Lice

In addition to treatment, you can take steps to help prevent reinfestation. Even though it’s highly unlikely for lice to spread through sharing belongings, such as hats, it’s still a wise idea to refrain from trading hair accessories, brushes, combs, and towels — especially with an individual with a known active case of head lice. Other ways to prevent getting and spreading lice include:

• Launder items. Change and launder the infested person’s pillow cases, pajamas, towels, and other items that their head was in direct contact with during the 24 to 48 hours before diagnosis. Machine wash it all in hot, soapy water, then dry on the hot cycle for at least 20 minutes. (18)
• Soak brushes. Submerge the infested person’s combs, brushes, barrettes, and hair bands in hot water for roughly 10 minutes. (3)
• Vacuum contacted surfaces. Use a vacuum on carpets, furniture, car seats, beds, and other items that have been in contact with the head of the person with infestation within the past 24 to 48 hours. (18)
• Seal up other items. Although it is rarely necessary, you can also place pillows and stuffed animals in a tightly sealed plastic bag for two weeks to suffocate any possible remaining nits or lice. (3)
• Avoid sprays. Not only is fumigating the home with pediculicide spray not needed in order to control head lice, inhalation of fumigant sprays can be toxic. (18)

While one may think a smart way to prevent the spread of lice is to keep children home from school, the American Academy of Pediatrics (AAP) disagrees. In fact, the AAP and the National Association of School Nurses contend that “no-nit” policies that keep children from attending school until all lice nits are removed should be discouraged. Instead, simply treat the infestation accordingly and discourage children from any direct head-to-head contact with other kids and adults. It’s also a good idea for parents to check in with classmates who likely had head-to-head contact with the infested child. (3)

According to the CDC, Black children in the United States are far less likely to wind up with a lice infestation than children of other ethnic groups. It’s thought that the lice most frequently found in the United States are less equipped to successfully grasp onto the shape and width of Black hair. (1)

But there is debate about whether this theory is accurate, says Candrice R. Heath, MD, assistant professor of dermatology in the Lewis Katz School of Medicine at Temple University in Philadelphia. “It’s also speculated that the use of oils and tightly coiled hair shafts may be reasons that lice occur less frequently in the hair of Black children.”

Of course, that doesn’t mean that Black children don’t get lice. They do. So it’s important to monitor any signs, such as scalp itching, regardless of a person’s race or ethnicity. It’s also important to adapt lice detection and lice removal techniques based on the texture of the child’s hair. For instance, head lice checks often involve using a comb with teeth that are closely spaced together. “When these standard lice combs are used on tightly coiled hair, it can be a challenge to adequately comb from the root without causing breakage or scalp pain,” says Dr. Heath. Instead, one might need to detangle the hair with a wide-toothed comb before using a lice comb. And when combing out hair during treatment, wetting and coating hair with conditioner will allow for a smoother comb-through.

Head lice are not the same as body lice or pubic lice. Body lice generally impacts those living in very cramped, crowded conditions who also have poor hygiene. These lice reside on clothing or bedding, but crawl onto skin several times a day to feed. They’re the only type of lice known to spread disease.

Learn More About Body Lice

Pubic lice are primarily spread via sexual contact and affect the hairs in the genital and anal areas. They are not known to transmit any diseases. (19)

Learn More About Pubic Lice

Diagnosing, treating, and — most importantly — preventing lice can be stressful and overwhelming. But it doesn’t have to be. Here are even more sources of information and support that can help.

Favorite Sites for Up-to-Date Lice Info

HealthyChildren.org

The writers and editors at Everyday Health often turn to HealthyChildren.org, the patient-friendly offshoot of the American Academy of Pediatrics, to learn the latest guidelines and news regarding all things related to children’s health. There’s no exception when it comes to head lice: This leading group of pediatric specialists provides information for parents on how to spot and safely treat lice in children. Plus, their website features a descriptive chart of all the head lice medicines approved by the FDA.

Centers for Disease Control and Prevention (CDC)

The CDC is, of course, a trusted source for all the most current information on head, body, and pubic lice, from antibiotic resistance to the latest treatment options. But the website also has a super helpful tool that allows you to sign up for condition-specific updates, so you are always the first to know about changes in prevention strategies, diagnosis best practices, and more. Simply click on the “Get Email Updates” option on the lice page, input your contact info, and you’ll automatically receive all the latest updates about lice.

Favorite Children’s Book About Lice

Bugs in My Hair! by David Shannon

Lice is annoying and sometimes embarrassing, and that’s exactly why we love that bestselling author and award-winning artist David Shannon shows kids (and parents) the funny side of head lice in his book Bugs in My Hair! This silly read will surely help quash some shame children may feel from a lice diagnosis. And as health editors and writers, the Everyday Health staff also loves that the book is dotted with facts about these creepy crawlers.

Favorite Videos to See Lice in Action

NPR

Here is a fascinating, up-close-and-personal look at head lice in action, crawling on strands of hair and moving from one person’s head to another. Plus, the short piece (just under four minutes) is peppered with need-to-know lice facts.

Merck Manual

Here’s another look at lice, this time pubic lice. While the video is animated, it still offers a solid sense of what this type of lice looks like. In addition to the video, there are several photographs of pubic lice, lice bites, lice on eyelashes, and more.

Favorite ‘What Do I Do?’ Flowchart

IdentifyUS

While IdentifyUS is not a nonprofit or a hospital, the writers and editors at Everyday Health still use this site as a go-to for head lice info. The reason? Its president and chief scientific officer is a trusted Harvard researcher, Richard J. Pollack, PhD. The site itself features a lot of helpful images of lice in various stages of life. In addition, you’ll find answers to a myriad of FAQs here. Our favorite feature is the handy flow chart that helps guide readers through tackling a possible infestation in their own homes.