It’s the call from the school nurse that no parent likes to hear: “Your child has head lice.” It is estimated that 6 to 12 million children under the age of 11 become infested with head lice every year. Though head lice are not exclusively a childhood ailment, the majority of people affected by head lice are young.
What do lice look like?
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Head lice are tiny parasites that live on the human head and feed on blood from the scalp. They are common in children and spread as a result of head-to-head human contact, not through pets.
Head lice are neither dangerous nor a sign of poor hygiene, and they do not spread any diseases. The main symptom of lice is itching.
People can treat a head lice infestation with over-the-counter (OTC) or prescription medication, which will kill the head lice.
Head lice have six legs and are usually grayish-white or tan. However, they can camouflage, so they may appear darker or lighter to match different hair colors.
Head lice have three stages in their lifecycle:
- eggs, which people often refer to as nits
- nymphs
- adult head lice
A nymph hatches from the egg and goes through several stages of growth before turning into an adult head louse. Nymphs look similar to adult head lice but are smaller, roughly the same size as a pinhead.
Adult head lice are about 2–3 millimeters (mm) in length, which is roughly the size of a sesame seed. Head lice crawl and cannot fly or jump.
People may need a magnifying glass to see head lice in detail.
The eggs, or nits, are tiny ovals that stick to the hair shaft, measuring 0.8 mm by 0.3 mm .
Female head lice lay the eggs within 6 mm of the scalp . People will often find them behind the ears and on the back of the neck.
The term nits can also refer to the empty egg casings that remain in the hair once the nymph has hatched. These are easier to see, especially on darker hair, as they are lighter, usually white or yellow.
The most common symptom of head lice is an itchy head. The itchiness is the result of a local allergic reaction to the lice bites.
People with head lice may also notice the following symptoms:
- a tickling sensation on the head
- the feeling of something moving on the head or through the hair
- difficulty sleeping as head lice become more active in darkness
- sores on the head from scratching
It is possible to develop an infection in the sores from scratching the head. People will need to see their doctor if they get a scalp infection.
Other conditions or items in the hair may look similar to head lice. People can sometimes mistake hairspray droplets, scabs, or dirt for nits.
Some other issues that can resemble head lice include:
Hair casts
Hair casts are white, tube-like debris, and they surround the hair shaft. They are usually 2 to 8 mm in length. They are uncommon and often have an association with other skin conditions.
Hair casts slide easily along the hair, whereas nits stick to it and are harder to remove. People may be able to remove hair casts with coal tar shampoo or a fine-toothed comb.
People with light-colored hair should be careful about using coal tar shampoo as it can discolor the hair.
Dandruff
Dandruff can look similar to head lice eggs and also causes the scalp to itch. Dandruff is a scalp condition in which dry skin comes away from the scalp in white flakes.
Dandruff lies on the scalp and comes away easily, whereas nits stick to the hair.
People can treat dandruff effectively using a dandruff shampoo. Dandruff shampoos are available in drug stores and online.
Scabies
Mites are small insects that cause scabies by digging into the skin and irritating it, which makes the skin itchy. Scabies usually affects the fingers, ankles, or wrists rather than the head.
People who notice a rash and uneven red lines on the skin or scalp might have scabies and should see their doctor, who may prescribe a topical cream as treatment.
Share on Pinterest A person should consult a doctor if OTC treatments are not effective.
To treat a head lice infestation, people can use medicines called pediculicides, which kill head lice. Some treatments are not suitable for young children, so it is best to check with a doctor or pharmacist before using them.
People can apply OTC head lice treatment topically to the head. It is important to follow the instructions on the medicine, which may advise a person to:
- wash the hair and dry it with a towel to remove excess water
- use a nonconditioning shampoo, as conditioner can create a barrier between the hair and the treatment
- follow the instructions on how long to leave the treatment on the hair
- rinse the hair over a sink instead of in the bath or shower to stop the treatment causing any irritation to the rest of the skin
- use warm rather than hot water
The treatment may cause a mild burning or irritating feeling. Afterward, people should use a nit comb to remove any dead or live lice that remain as well as the eggs.
Both of these treatments only kill live head lice, not the unhatched eggs, so people may need to apply a second dose of treatment 9 to 10 days after the initial one.
If OTC solutions are not effective, people can see their doctor. They may need to use prescription medicine that contains:
- benzyl alcohol
- malathion
- spinosad
- ivermectin
People should follow their doctor’s instructions when applying prescription head lice treatment, as misusing or overusing it may cause side effects.
Alongside treatments, people can take action to help limit lice and prevent a reinfestation, though treating all household members with active lice at the same time is usually sufficient. Some tips for prevention include:
- washing any items of clothing or bedding that people have used in the last couple of days in a hot wash above 128.3°F (53.5°C) to kill the lice
- vacuuming floors and furniture onto which people with head lice may shed hair
- avoiding sharing any hair accessories, clothing, or items that come in contact with the head of a person with lice
Head lice can only survive for up to 2 days away from the human head, so they will not last long in any surrounding areas.
Shampoos for head lice are available for purchase in drug stores, pharmacies, and online.
Head lice are harmless, but they are contagious. They can cause itching and irritation and can be a source of anxiety for some people.
People can use OTC medicines to treat head lice. If these are not effective, a doctor can recommend a prescription medicine instead.
- Bites and Stings
- Dermatology
- Pediatrics / Children’s Health
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- Dandruff: How to treat. (n.d.).
https://www.aad.org/public/diseases/hair-and-scalp-problems/dandruff-how-to-treat - Devore, C. D., & Shutze, G. E. (2015). Head lice.
https://pediatrics.aappublications.org/content/135/5/e1355 - Lice and scabies. (2012).
https://www.aafp.org/afp/2012/0915/p535-s1.html - Lokhande, A. J., & Sutaria, A. (2017). Adult onset hair casts: Nits which do not itch!
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5551310/ - Parasites: Head lice. (2013).
https://www.cdc.gov/parasites/lice/head/index.html
What Do Lice Look Like?
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It’s the call from the school nurse that no parent likes to hear: “Your child has head lice.” It is estimated that 6 to 12 million children under the age of 11 become infested with head lice every year. Though head lice are not exclusively a childhood ailment, the majority of people affected by head lice are young.
The head louse, scientific term Pediculus humanus capitis, is a parasite that feeds on human blood. Learning what head lice look like and how to detect them can help control an infestation before it spreads through the entire household.
Three forms of head lice exist: nits, nymphs, and mature adults. Nits are lice eggs that attach to the hair shaft and usually hatch within a week. The microscopic eggs are easy to mistake for dandruff or residue from hair styling products.
Once the eggs hatch, lice are known as nymphs, an immature form of the parasite that is grayish tan in color. After nine to 12 days the nymphs mature into adults, the average size of which is roughly 2–3 millimeters, or about the size of a sesame seed.
Head lice feed on blood and therefore stay close to the scalp where there is an abundant supply of food. After the nits hatch, they move from the hair shafts to your scalp to find sustenance.
You’ll find nymph and adult lice most commonly on the scalp around the back of your neck and ears. They might also live in your eyebrows or on your eyelashes. When fed, head lice can live for up to a month, but they will die within a day or two if they are not able to feed on blood.
Head lice are insects, but they can’t fly. Instead, they crawl around in your hair and on your scalp to get nourishment. Lice are spread through close personal contact. The parasites crawl onto your clothing, hairbrushes, hats, towels, and any other personal belongings.
If a friend or family member shares your comb or scarf, the head lice can crawl onto the new host and lay eggs, spreading the infestation. Female head lice can lay several eggs each day. Household pets and other animals do not spread head lice to humans.
Some people experience the uncomfortable symptoms of head lice before noticing them in the hair, while others are asymptomatic. Head lice bite you in order to feed off your blood. The parasites’ saliva is irritating to many people, causing itching of the scalp. You might develop sores or red, raised bumps on your scalp from scratching your head without realizing why you are itchy at first.
Other symptoms that alert you to a case of head lice include a ticklish feeling on your head, especially at night. The head louse is a nocturnal creature and is more active in the dark than during the light of day.
A visual inspection of your hair and scalp is usually effective in detecting head lice, though the creatures are so small that they can be difficult to spot with the naked eye.
Parting your hair in small sections and literally going through each section with a fine-tooth comb is a painstaking but necessary step to find and remove head lice. A bright light and a magnifying glass are useful tools to aid in the detection and diagnostic process.
Head lice are treated through manual removal with a comb as well as special shampoos containing chemicals that kill lice. Even if just one nit or adult louse is found, treatment is advised to reduce the threat of a full infestation.
Clothing, bedding, and towels must all be washed in hot water to control the infestation. Vacuuming carpets and furniture upholstery is another component of the treatment process for head lice.
The good news is while a head lice infestation can be annoying and possibly uncomfortable, this common condition is treatable. Complications are rare and generally limited to skin infections caused by scratching.
Prevent head lice by instituting a “no sharing” rule for personal belongings such as combs, hairbrushes, towels, hats, and bedding.
Last medically reviewed on July 18, 2017
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