Although itching may be a sign of a lice infestation, most often individuals are asymptomatic. Keep in mind that although the only reliable sign of an infestation is the presence of a live louse or nymph (juvenile louse), the presence of nits may be a sign that there is or has been an active infestation.
Head lice (Pediculus humanus capitis) are parasites that can be found on the heads of people. Pediculosis is the term for an infection with head lice. (The head louse, Pediculus humanus capitis, is different from the pubic louse (Pthirus pubis), which causes pubic hair infections, and the body louse (Pediculus humanus corporis).
Head lice infestation is very common, and it has been around since ancient times. While the exact frequency of infections is unknown, estimates range from 6-12 million cases annually.
Anyone who comes in close contact with someone who already has head lice, or even their contaminated clothing and other belongings, is at risk for acquiring head lice. So it is easy to transmit head lice from one person to another. Preschool and elementary-school children (3-11 years of age) and their families are infected most often. Girls contract head lice more often than boys, and women contract more head lice than men.
A child can contract head lice in a number of ways.
There are three forms of lice, namely the nit, the nymph, and the adult louse.
Nit: Nits are lice eggs. Nits are hard to see and are often confused with dandruff or hair-spray droplets. Nits are found firmly attached to the hair shaft. They are oval shaped, 2-3 mm in length and usually yellow to white in color. Nits take about a week to hatch.
Nymph: The nit hatches into a baby louse called a nymph. It looks like an adult head louse but is smaller. Nymphs mature into adults about seven days after hatching. To live, the nymph must feed on human blood.
Adult: The adult louse is about the size of a sesame seed, has six legs, and is tan to grayish-white in color. In people with dark hair, the adult louse looks darker. Females lay nits; they are usually larger than males. Adult lice can live up to 30 days on a person's head. To live, adult lice need to feed on human blood. If the louse falls off a person, it dies within two days.
Life cycle: The nits hatch into nymphs, which become full grown lice. In order to produce more nits, the adult lice must mate.
Head lice are most frequently located on the scalp behind the ears and near the neckline at the back of the neck. Head lice hold on to hair with hook-like claws that are found at the end of each of their six legs. Head lice are rarely found on the body, eyelashes, or eyebrows.
Head lice are often confused with dandruff. Dandruff can easily be distinguished by combing the hair or even just rubbing. Dandruff should be easily removed, but the nits of head lice are firmly attached to the hair shaft.
The signs and symptoms of a head lice infestation are
Head lice can be detected by looking closely through the hair and scalp for nits, nymphs, or adults. Locating a nymph or adult may be difficult; there are usually only a few of them, and they can move quickly from searching fingers. However, the presence of nits close to the scalp confirms that a person is infested. If the nits are located more than ¼ inch from the scalp, the infestation is probably an old one. If you are not sure whether or not a person has head lice, the diagnosis should be made by a health care professional, school nurse, or a professional from the local health department or agricultural extension service. The nits of head lice are easily visible with a microscope. Dr. Ioffe-Uspensky performed a study that showed that using a louse comb was better than visual inspection alone when screening for lice infestations.
A black light is sometimes used to see if there are nits with live lice in them. Some reports indicate that nits with live lice will fluoresce.
For effective elimination of head lice, the infested individual, family members that are also infested, and the home must all be treated. It is important to remember that treatment should only be started if there are clearly live lice identified. According to the American Academy of Pediatrics in a recent clinical report, "The ideal treatment of lice should be safe, free of toxic chemicals, readily available without a prescription, easy to use, effective and inexpensive."
Over-the-counter (OTC) or prescription medications are used to treat the affected people and their families. Follow these treatment steps:
Treating the whole house is a laborious but important task. Follow these steps:
No. Although anyone living with an infested person can get head lice, you don't need to be treated. Check household contacts for lice and nits every two to three days. Treat if lice and nits are found.
For children under 2 years old, remove nits, nymphs (immature adult lice), and adult lice by hand, and see a health care professional. Permethrins are approved for children older than 2 months of age; however, this should too be done after consultation with your physician.
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Many head lice medicines are available at drugstores. Each OTC product usually contains one of the following active ingredients:
Malathion .5% (Ovide): Malathion is an organophosphate insecticide that is only available as a prescription and it kills live lice (pediculicidal) and the lice inside the eggs/nits (ovicidal). It has actually been pulled off the market twice due to safety concerns, but it was reintroduced in the United States (USA) in 1999 due to increasing resistance of head lice to other treatments. The formulation in the United States contains terpineol dipentene, isopropyl alcohol, and pine needle oil, both of which have pediculicidal properties. The product is used differently than other compounds. The product is extremely flammable and should never be around heat, hair dryers, or curling irons. The product is applied to dry hair until the scalp and hair are thoroughly coated. Make sure that the area behind the ears and the back of the neck are covered. Let the hair dry naturally (no hair dryers). The product is left in place for eight to 12 hours. After eight to 12 hours, wash and rinse the hair with shampoo. Use a nit comb (fine-toothed comb) to remove any nits. If live lice are noted after seven days, retreat. It is currently recommended only for individuals 6 years of age up to 60 years of age.
Benzyl alcohol 5% (Ulesfia): Benzyl alcohol is available in the U.S. as a 5% lotion. The product is applied to dry hair until the scalp and hair are thoroughly coated. Make sure that the area behind the ears and the back of the neck are covered. Leave it in the hair for only 10 minutes and then rinse thoroughly in a sink. Do not use a shower to avoid getting the solution over the rest of the body. You can immediately wash your hair with regular shampoo. It is not ovicidal and needs to be repeated in one week if there is any evidence of live lice.
Spinosad (Natroba): Spinosad is a derived from soil bacteria. It is both pediculicidal (kills the live lice) and ovicidal (kills the lice inside the eggs/nits). It is moderately more effective than the over-the-counter treatments but is available only by prescription and is very expensive. If live lice are noted after seven days, retreat. It is approved in children 6 months of age and older and contains benzyl alcohol, as well.
Ivermectin (Sklice): Ivermectin is available as both a 0.5% lotion (which is FDA approved for the treatment of lice) and as an oral medication (which is not approved in the U.S. for treatment of lice). It has been used to treat helminthic infestations (worms) for many years. Generally, only one treatment is needed. It is pediculocidal (kills live lice). Although it is not ovicidal (kills the lice inside the eggs/nits), it appears to prevent nymphs (newly hatched lice) from surviving. Topical ivermectin lotion may be used in the treatment of lice in children 6 months of age and older. While oral invermectin is commonly used in other countries for lice, it is currently not approved for the treatment of head lice in the U.S. In countries where it is approved, the dosage is usually a single dose, which is often repeated in nine days.
Lindane (Kwell): It is important to note that lindane 1% (Kwell) is no longer recommended as a treatment option for head lice due to its toxicity in children. It can still be prescribed, but most experts recommend against its usage.
Other treatments such as permethrin 5%, crotamiton 10%, and sulfamethoxazole-trimethoprim (Bactrim) are not currently approved by the FDA for the use in the treatment of head lice.
If unsure, please consult with a pharmacist or health care professional.
When using head lice medicine, as with any medicine, always follow the instructions provided.
When treating head lice,
Occlusion therapy, nit combing, and hair removal have not been proven to be fully effective in completely eradicating head lice.
Home remedies that have been tried include vinegar, mayonnaise, petroleum jelly, olive oil, butter, rubbing alcohol, and prolonged water submersion. These all fail to eliminate infestation, because these therapies do not kill all of the eggs or lice. This is believed due to the specialized way the parasite "breathes."
Hair removal has never been proven to be effective, but since the louse requires a hair shaft to lay its eggs, it should prevent the lice from multiplying. This is not always considered a desirable option for many children.
There is also a device that uses hot air to kill the lice. The device, OneCure, is an FDA-cleared home device. Currently, there are no published studies looking at the efficacy of this product.
No. Spraying the house is not recommended. Fumigants and room sprays can be toxic if inhaled.
No. Vacuuming floors and furniture is sufficient to treat the house.
It's not always so easy to prevent head lice 100% of the time since it is a common infestation. Whenever possible, do not share hats or head coverings. Also avoid sharing combs and brushes with other individuals, since it can be transferred this way. If exposed to another individual diagnosed with head lice, continue to check the hair for eggs or adult lice every couple of days, but do not treat unless head lice are discovered.
Once diagnosed and treated effectively, the prognosis is excellent. Eradication is of course the goal, and occasionally retreatment and alternative treatments are needed. Always consult a health care professional if one needs advice.
The American Academy of Pediatrics no longer recommends the so-called "no nit" policy of some schools and day cares. There is a very low risk of spreading lice within the classroom, and nits may not actually represent the continued presence of live lice.
Although a child could get a new infestation from being reexposed to an infested individual, self-reinfestation is the most common way for the infestation to recur. The CDC recommends checking the individual for two to three weeks to ensure that there are no new nits or lice.
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