What are head lice?

Head lice are small, wingless, grayish-white insects, about 1/16 to 1/8 inch in length, which spend their entire life cycle on the head of humans as bloodsucking external parasites. Head lice have claws especially adapted for clinging to hair shafts.

Where are head lice found?

Head lice are rarely found off the head. They are most commonly found in the hair above and behind the ears and near the nape of the neck.

What is a "nit"?

The nit is a louse egg which is always glued by the female to the base of the hair shaft, only three to four mm from the scalp. A female can lay 50-150 eggs over a three to four-week period.

What is the life cycle of the head louse?

Head lice eggs hatch in seven to nine days into the first nymph stage, which looks like a miniature adult. The nymph takes a blood meal by biting the scalp soon after hatching and continues to feed every three to six hours. In about nine days, the louse will have passed through two more nymphal stages and have achieved the adult stage. The adult remains on the head for its entire lifetime.

Is cleanliness important in preventing head lice?

No. Infestations are not prevented or influenced by personal or household cleanliness, use of shampoos or length of hair. All social and economic groups can be affected by head lice, but African Americans are much less frequently infested than other racial groups.

How does a person get head lice?

Head lice are usually transmitted by close personal contact with the hair of an infested person. However, transmission can also occur through the sharing of personal items, such as hats, headbands or coats, or the storage of these items together, such as in a school classroom. At home, the sharing of such items as combs, brushes, towels, soft toys and bed sheets can also result in transmission.

How long do head lice live away from the head?

Head lice cannot normally survive for more than 48 hours without a blood meal; therefore, they will not survive for long off the head. Very few nits will hatch away from the head, and any nymphs which emerge will die very soon without a blood meal.

What are the symptoms of pediculosis (an infestation of head lice)?

While persons with light infestations may not notice any problem, itching is the most common symptom, caused by an allergic reaction to the bites. Other symptoms include a tickling feeling of something moving in the hair, irritability, and sores on the head caused by scratching.

How can you detect a head lice infestation?

Detection of nits, nymphs or adult lice is the only way to confirm the presence of lice. It requires a thorough examination of the scalp. Nymphs and adults move quickly and are often difficult to observe. Finding nits close to the scalp is the usual way to confirm an infestation. However, finding nits which are more than 1/4 inch from the scalp usually indicates that they are old and not viable, despite being firmly cemented to the hair.

Can head lice transmit any diseases?

Head lice do not transmit any diseases. Sores caused by scratching and crusting can result in secondary bacterial infections.

What is the treatment for pediculosis?

To treat a head lice infestation, an over-the-counter (OTC) or prescription shampoo, lotion or cream rinse is used. The instructions of your health care provider and the product label should be followed carefully when using any pesticide medication. Treatment failures are common. If active lice are observed 8-12 hours after treatment, consult again with your health care provider regarding the use of a different product.

Will the medications kill the nits?

There is no guarantee that any product is completely ovicidal (kills all the eggs). Thus, it is extremely important that the hair and scalp be thoroughly checked every 2-3 days after treatment and all nits and lice are removed with a nit comb. Most head lice products recommend a second treatment in seven to 10 days after the first treatment in order to kill any nymphs which emerge from the eggs.

How effective are alternative treatments?

Many alternatives to pediculicides (products designed to treat lice) have been promoted because of treatment failures. Unfortunately, there is little documentation that these methods are effective at killing the lice and nits on the head. Some of these remedies include olive oil, mayonnaise, tea tree oil, petroleum jelly and hair dryers. Among substances which should never be used are kerosene, gasoline and pesticides not registered for treatment of lice, such as diazinon.

How difficult is it to remove all the nits?

Hair should be examined in small sections and the nits removed with the nit comb (some people prefer flea combs, fingernails or tweezers). Certain commercial products and white vinegar may help to loosen the glue holding the nits to the hair, but it will often take many hours over a period of days to remove all of the nits. Because of many reports of lice which are resistant to pediculicides, it is particularly important to remove all nits close to the scalp.

How can my family avoid being infested?

All contacts of an infested person should be examined and treated as necessary. Bed mates and brothers and sisters should also be treated. The examination and treatment of contacts, if necessary, should be done simultaneously. Treated persons should be checked for at least two weeks to be sure the lice and nits are gone. Family members should avoid sharing combs, brushes, towels and other personal items.

What else can be done to prevent the spread of head lice?

Any stray lice and nits on clothing, towels and bedding that the infested person touched during the two days before treatment will be killed by machine washing and drying at temperatures over 128oF. Dry cleaning also kills lice. Stuffed animals and clothing that cannot be washed or dry cleaned may be sealed in a plastic bag for two weeks to kill all lice and nits. Combs and brushes can be soaked for an hour in 2% Lysol solution or heated in a pan of water to 120oF for ten minutes.

Should insecticide sprays be used in the house or school?

Since lice do not survive for long off the scalp, the use of environmental insecticide sprays is not necessary. Vacuuming carpets and upholstered furniture will remove any stray lice or nits.

What is the school's role in the prevention and control of pediculosis in children?

Because elementary schools and day care centers bring large numbers of children together on a daily basis, they serve as a focus for the transmission of head lice. Head lice are commonly spread by direct head to head contact in the school setting. However, the sharing of personal items such as hats, brushes, combs, etc. may also spread lice between children. It is important for schools to have established procedures for screening of children, education of parents and children, follow-up measures and clear admission and restriction policies in order to prevent or control an outbreak. Some schools have adopted a nit free ("no nit") policy which requires that a child be completely free of nits before readmission is permitted.

Other measures may also help control a school outbreak. Classroom activities involving contact between students may be temporarily suspended, and children may be asked to store coats, hats, scarves, etc., in separate bags to avoid the transmission of lice.

Control measures for head lice will be most effective when the entire community is well informed about head lice and how they are spread, and all families become active participants in the prevention of head lice.