What is nits in hair?
Head lice are small, wingless insects that live, breed and feed on the human scalp. They do not generally carry or transmit disease. Head lice have existed for millions of years and, in fact, predate human evolution.
Direct contact is required for transmission from person to person. Lice will crawl from head to head without discrimination.
A female louse lays 3 to 8 eggs (nits) per day. The eggs are firmly attached to the hair fibres, within 1.5 cm of the scalp, and rely on warmth from the head to hatch. Head lice do not have wings or jumping legs, so they cannot fly or jump from head to head. They can only crawl.
People catch head lice from direct head-to-head contact with another person who has head lice. This can happen when people play, cuddle or work closely together. Head lice are most common among children and their families.
If your family has head lice, tell anyone who has had head-to-head contact with them, so that they can check and treat their family if needed. There is no need to treat the whole family, unless they also have head lice.
Concentrate on treating the affected person’s head. There is no evidence to suggest that you need to clean the house or the classroom. The only linen that requires changing is the affected person’s pillowcase. Wash it in hot water (60 ºC) or dry it in a clothes dryer set to warm or hot.
Itchiness may not disappear immediately after treatment. Persistent itch without evidence of persistent infection is not a reason to repeat the treatment. There are other reasons why your scalp might feel itchy.
Some people who have a head lice infestation do not itch. It is possible to have head lice and not feel the need to scratch your head. This means that absence of itch is not a reliable sign that you do not have head lice.
If you suspect someone might have been exposed to head lice you will need to closely inspect that person’s hair and scalp.
So what are you looking for? Head lice eggs are oval, and the size of a pinhead. They are firmly attached to the hair shaft and cannot be brushed off. (A live egg will make a ‘pop’ sound if you crush it between your fingernails.)
A louse is a small, wingless, whitish-brown to reddish-brown insect. They have 6 legs, which end in a claw. Like this:
The easiest and most effective way to find head lice is to use the conditioner and comb treatment weekly. This includes:
Note: If the person has been treated recently and only hatched eggs are found, you may not have to treat them again, since the eggs could be from the old infection. A hatched egg looks like an egg with its top cut off:
The 2 preferred treatment options available for initially treating head lice are the ‘conditioner and comb’ method, and the use of an insecticide.
Any head lice treatment product you choose should carry an Australian Registered (AUST R) or Australian Listed (AUST L) numberExternal Link on the outer packaging. These numbers show that the product is accepted by the Therapeutic Goods Administration for supply in Australia.
If you use a lotion, apply the product to dry hair. For shampoo products, wet the hair, but use as little water as possible.
Head lice live in the hair and go to the scalp to feed. Therefore, head lice products must be applied to all parts of the hair.
Once the treatment has been done according to the instructions on the packet, comb through the hair again with the fine tooth head lice comb. This will help to remove the dead eggs and lice, and possibly any eggs still living.
This is also a good time to check whether the removed lice have been killed by the treatment or are still alive. (If they are still alive this probably means that they are resistant to the insecticide.)
Care should be taken when using head lice treatment products:
All products can cause reactions. If you are unsure, check with your pharmacist or doctor.
No topical insecticide treatment kills 100% of the eggs, so treatment must involve 2 applications, 7 days apart. (This kills the lice that hatched from the eggs that didn’t die the first time around.)
If you choose not to use an insecticide, the comb and conditioner method described above can be used every second day until no live lice have been found for 10 days.
Insecticide resistance is common, so you need to check that the lice you comb out are dead. If the insecticide has worked, the lice will be dead within 20 minutes. If the lice are not dead, the treatment has not worked and the lice are resistant to the product and all products containing the same active compound.
The active compounds in head lice products are:
If a product with one of these active compounds has not worked for you, you can try another, or speak to your pharmacist or doctor.
If the initial treatments have failed and live lice are still being removed with the conditioner and comb treatment, see your doctor for a referral to a dermatologist for specialist treatment.
A dermatologist may prescribe ivermectinExternal Link . This is a tablet taken twice, 7 days apart. It is highly effective in treating head lice.
Fun fact: The Nobel Prize for Medicine and Physiology in 2015 was awarded for the discovery of this family of medications.
Head lice combs with long rounded stainless steel teeth, positioned very close together, are the most effective. However, any head lice comb can be used. A plastic head lice comb is often provided when you buy a head lice insecticide product (in the packet with the shampoo or lotion).
According to the Public Health and Wellbeing Regulations 2009, children with untreated head lice are not permitted to attend school or children’s service centres. However, once treatment has started, they may attend, even if there are still some eggs present.
The head louse, or Pediculus humanus capitis, is a parasitic insect that can be found on the head, eyebrows, and eyelashes of people. Head lice feed on human blood several times a day and live close to the human scalp. Head lice are not known to spread disease.
Head lice are found worldwide. In the United States, infestation with head lice is most common among pre-school children attending child care, elementary schoolchildren, and the household members of infested children. Although reliable data on how many people in the United States get head lice each year are not available, an estimated 6 million to 12 million infestations occur each year in the United States among children 3 to 11 years of age. In the United States, infestation with head lice is much less common among African-Americans than among persons of other races, possibly because the claws of the head louse found most frequently in the United States are better adapted for grasping the shape and width of the hair shaft of other races.
Head lice move by crawling; they cannot hop or fly. Head lice are spread by direct contact with the hair of an infested person. Anyone who comes in head-to-head contact with someone who already has head lice is at greatest risk. Spread by contact with clothing (such as hats, scarves, coats) or other personal items (such as combs, brushes, or towels) used by an infested person is uncommon. Personal hygiene or cleanliness in the home or school has nothing to do with getting head lice.
Head lice have three forms: the egg (also called a nit), the nymph, and the adult.
Egg/Nit: Nits are lice eggs laid by the adult female head louse at the base of the hair shaft nearest the scalp. Nits are firmly attached to the hair shaft and are oval-shaped and very small (about the size of a knot in thread) and hard to see. Nits often appear yellow or white although live nits sometimes appear to be the same color as the hair of the infested person. Nits are often confused with dandruff, scabs, or hair spray droplets. Head lice nits usually take about 8–9 days to hatch. Eggs that are likely to hatch are usually located no more than ¼ inch from the base of the hair shaft. Nits located further than ¼ inch from the base of hair shaft may very well be already hatched, non-viable nits, or empty nits or casings. This is difficult to distinguish with the naked eye.
Nymph: A nymph is an immature louse that hatches from the nit. A nymph looks like an adult head louse, but is smaller. To live, a nymph must feed on blood. Nymphs mature into adults about 9–12 days after hatching from the nit.
Adult: The fully grown and developed adult louse is about the size of a sesame seed, has six legs, and is tan to grayish-white in color. Adult head lice may look darker in persons with dark hair than in persons with light hair. To survive, adult head lice must feed on blood. An adult head louse can live about 30 days on a person’s head but will die within one or two days if it falls off a person. Adult female head lice are usually larger than males and can lay about six eggs each day.
Head lice and head lice nits are found almost exclusively on the scalp, particularly around and behind the ears and near the neckline at the back of the head. Head lice or head lice nits sometimes are found on the eyelashes or eyebrows but this is uncommon. Head lice hold tightly to hair with hook-like claws at the end of each of their six legs. Head lice nits are cemented firmly to the hair shaft and can be difficult to remove even after the nymphs hatch and empty casings remain.
Head-to-head contact with an already infested person is the most common way to get head lice. Head-to-head contact is common during play at school, at home, and elsewhere (sports activities, playground, slumber parties, camp).
Although uncommon, head lice can be spread by sharing clothing or belongings. This happens when lice crawl, or nits attached to shed hair hatch, and get on the shared clothing or belongings. Examples include:
Dogs, cats, and other pets do not play a role in the spread of head lice.
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The diagnosis of a head lice infestation is best made by finding a live nymph or adult louse on the scalp or hair of a person. Because nymphs and adult lice are very small, move quickly, and avoid light, they can be difficult to find. Use of a magnifying lens and a fine-toothed comb may be helpful to find live lice. If crawling lice are not seen, finding nits firmly attached within a ¼ inch of base of the hair shafts strongly suggests, but does not confirm, that a person is infested and should be treated. Nits that are attached more than ¼ inch from the base of the hair shaft are almost always dead or already hatched. Nits are often confused with other things found in the hair such as dandruff, hair spray droplets, and dirt particles. If no live nymphs or adult lice are seen, and the only nits found are more than ¼-inch from the scalp, the infestation is probably old and no longer active and does not need to be treated.
If you are not sure if a person has head lice, the diagnosis should be made by their health care provider, local health department, or other person trained to identify live head lice.
More on: Treatment
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Most health departments do not require reporting of head lice infestation. However, it may be beneficial for the sake of others to share information with school nurses, parents of classmates, and others about contact with head lice.
No. CDC is not a regulatory agency. School head lice policies often are determined by local school boards. Local health departments may have guidelines that address school head lice policies; check with your local and state health departments to see if they have such recommendations.
More on: Head Lice Information for Schools
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Head lice should not be considered as a medical or public health hazard. Head lice are not known to spread disease. Head lice can be an annoyance because their presence may cause itching and loss of sleep. Sometimes the itching can lead to excessive scratching that can sometimes increase the chance of a secondary skin infection.
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Head lice are spread most commonly by direct contact with the hair of an infested person. Spread by contact with inanimate objects and personal belongings may occur but is very uncommon. Head lice feet are specially adapted for holding onto human hair. Head lice would have difficulty attaching firmly to smooth or slippery surfaces like plastic, metal, polished synthetic leathers, and other similar materials.
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Head lice and their eggs (nits) soon perish if separated from their human host. Adult head lice can live only a day or so off the human head without blood for feeding. Nymphs (young head lice) can live only for several hours without feeding on a human. Nits (head lice eggs) generally die within a week away from their human host and cannot hatch at a temperature lower than that close to the human scalp. For these reasons, the risk of transmission of head lice from a wig or other hairpiece is extremely small, particularly if the wig or hairpiece has not been worn within the preceding 48 hours by someone who is actively infested with live head lice.
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Data show that head lice can survive under water for several hours but are unlikely to be spread by the water in a swimming pool. Head lice have been seen to hold tightly to human hair and not let go when submerged under water. Chlorine levels found in pool water do not kill head lice.
Head lice may be spread by sharing towels or other items that have been in contact with an infested person’s hair, although such spread is uncommon. Children should be taught not to share towels, hair brushes, and similar items either at poolside or in the changing room.
Swimming or washing the hair within 1–2 days after treatment with some head lice medicines might make some treatments less effective. Seek the advice of your health care provider or health department if you have questions.
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This information is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the parasites described above or think that you may have a parasitic infection, consult a health care provider.
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