What You Should Know About. . .

Head Lice

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, no more than 1/8 inch 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.

Will cleanliness prevent 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 direct contact with the head or hair of an infested person. Transmission can also occur through the sharing of personal items, such as hats, headbands or coats, or the storage of these items together, however this is much less likely.

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 may include a tickling feeling of something moving in the hair 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. 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. Treatment failures are common, as head lice can be resistant to some products.

Will the medications kill the nits?

Most products are not completely ovicidal (kills all the eggs). 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.

Is it necessary to remove all the nits?

Removal of nits after treatment with a pediculicide is not necessary to prevent spread, because only live lice cause an infestation. Individuals may want to remove nits for aesthetic reasons or to decrease diagnostic confusion.

How difficult is it to remove all the nits?

Nit removal can be difficult and tedious. Fine-toothed “nit combs” are available to make the process easier (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.

How can my family avoid being infested?

All close contacts and family members of an infested person should be examined, but only those with live lice or nits within 1⁄2 inch of the scalp should be treated. It may also be prudent to treat family members who share a bed with the infested person, even if no live lice are found.

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

It is probably impossible to totally prevent head lice infestations. Young children come into close head-to-head contact with each other frequently. It is prudent for children to be taught not to share personal items such as combs, brushes, and hats.

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 a child with an active head lice infestation has likely had the infestation for a month or more by the time it is discovered, he or she should be allowed to remain in class, but be discouraged from close direct head contact with others. The child’s parent or guardian should be notified of the infestation that day by telephone, or by a note sent home with the child at the end of the school day. The parent or guardian should be advised that prompt proper treatment of this condition is in the best interest of the child and his or her classmates.

It may be prudent to check other children in the school who were most likely to have had direct head-to-head contact with the infested child, however classroom or school-wide screening has not been proven to be necessary or effective at controlling the spread of head lice.

Some schools have implemented “no nit” policies under which a child is not allowed to return to school until all nits are removed. The American Academy of Pediatrics and the National Association of School Nurses discourages such policies.

Reference: State of New Jersey Department of Health (http://www.state.nj.us/health/cd/documents/f_headlice.pdf)