Head lice are small parasitic insects that have adapted to live off of human scalps. Having head lice is not a sign of being unclean or of neglect. Head lice cannot jump or fly. They are mostly acquired from head-to-head contact between children, but can also be transferred by objects such as combs, brushes, hair accessories and even furniture where a person rests his or her head.
Head lice need a blood meal once a day, or else they die. They become adults 7 to 12 days after hatching, and adult female lice lay approximately 6 eggs ("nits") a day. The eggs are yellowish-white, and are cemented to the hair shaft at the level of the scalp. The nits are often the only visible sign of having lice. Once laid, the eggs then hatch about 7 days later. There is no good way to determine whether or not an egg is "alive" or not without using a microscope.
Besides the visible signs of lice and nits, other symptoms of having head lice include itching, swollen lymph nodes at the back of the head, and sometimes a secondary bacterial infection of the scalp. The lice themselves do not spread disease.
Because the treatment of head lice involves the use of insecticides, it is important to make sure that there really is a lice infestation before starting treatment. Finding one or more live lice, or seeing the appearance of new nits at the scalp level are good ways to confirm the diagnosis. Many times, dandruff and even dirt can be mistaken for nits. If lice are present, treatment options are listed below. It is not necessary to treat everyone in the family, but each person in the house should be inspected for possible lice.
Treatment
Shampoos and Creme Rinses
One group of shampoos and rinses contain insecticides called pyrethroids. These include Nix, Rid, Pronto and similar non-prescription products. Despite what you may read on the label, these products have very limited killing ability and should be repeated in 10 days to kill the lice that hatched from the eggs that were present at the time of the first treatment. For this reason, it is a good idea to get out as many of the nits that are close to the scalp as you can after the treatment. Lice take approximately 24 hours to die from these shampoos, so don't be surprised if you see live live a few hours after the treatment.
There are other products that are available by prescription only. Ovide (malathion) and Ulefsia were recently approved. Kwell (lindane) has been around for many years, but should only be used as the last resort due to possible side effects.
Mechanical removal
Mechanically removing lice and nits can be an effective but time-consuming method. An infestation may be eliminated by combing each day to remove the live lice (including those that have hatched since the previous day). Comb daily until no live lice are discovered for about two weeks. Use illumination, magnification and a good louse or nit metal comb to locate and remove the offending insects. Although the hair may appear to have a lot of eggs, there generally are fewer than a dozen active lice on the head at any time. Adult female lice usually cement each egg to the base of a hair shaft near the skin. As the hair grows (from the base), these attached eggs move away from the scalp. Eggs more than one-half of one inch away from the scalp are nearly always hatched and do not, by themselves, indicate an active infestation.
Louse/nit combs can be useful in removing lice and eggs. Some louse/nit combs are better than others; a good metal comb is called the LiceMeister. Whereas straight hair is usually readily combed, tight curls may present an impossible and impractical challenge. Hair should be cleaned and well-combed or brushed to remove tangles before attempting to use a louse/nit comb. You may wish to dampen the hair with water from a spray bottle. Clean the louse comb frequently to remove any caught lice or eggs. It may require several hours each night for several nights to tackle the problem. An entertaining video may help keep your child occupied during this exercise. Sit behind the child, and use a suitably bright light (and magnification if available), to inspect and comb through the hair, one small section at a time. Repeat until no more active lice are observed.
Suffocation of the Lice
While a popular non-insecticide method to treat lice, this method has as many failures as successes. Typically, a product is put on the hair to cover the scalp with the intention of depriving the lice of oxygen overnight; the child wears a showercap to bed to prevent getting the hair product on the pillows. A common product that parents try is petroleum jelly, but it takes days to wash out of the hair and is not recommended. Other common choices include mayonnaise, olive oil and pomades. Motor or machine oils are not recommended.
Oral medications
Because head lice depend on bacteria functioning in their gut, some doctors have speculated that killing the bacteria would kill the lice. By giving an antibiotic to the child with lice, the lice would take up the antibiotic into their gut when they take up blood form the child's scalp. This has not yet been well tested, and is a last resort for resistant lice infestations.
Other researchers have tested antiparisitic drugs such as ivermectin against head lice. At the present, these drugs have not yet been approved by the FDA for the treatment of head lice.
Care of the Household
On the day of the first treatment of your child's head, there are certain things you should do to clothes and other items around your house to avoid reinfestation. Since heat kills lice, items that are washable should be washed with hot water. Bleach is not necessary. Items that can't be washed may be put in a clothes dryer for about 20 minutes. Items that can't be washed and are too large to fit into a dryer should be vacuumed. Remember to vacuum couches, mattresses and inside your car. You may wish to repeat these steps 10 days later, at the same time when you retreat your child's hair.
We do not recommend the use of the sprays that are sold to kill lice on upholstery and mattresses, as this is usually overkill and adds unnecessary pesticides to your house.
Combs and brushes should be washed in a solution of hot water and lice shampoo once daily until you are sure the lice infestation is over. Hair accessories should be placed in a closed container for at least 48 hours.
While head lice do need hair shafts to hang on to, we normally don't recommend haircuts, since lice can still hang on to short hairs, and not very many children appreciate having their heads shaved.
The type of head lice that lives on humans cannot live on dogs, cats or other animals, so you do not need to treat your pets.