They only live on the scalp and human hair. They aren't found on other parts of the body. Body lice, which are not common in the U.S., are related to head lice but live mostly on clothing, near the skin. A third type of lice found on humans is pubic or crab lice. These are usually found in a person's pubic area.

Head lice are parasites that feed on human blood. They bite the scalp but cannot burrow into it. Head lice don't pass on infections through their bite, but their saliva and feces can prompt an allergic reaction in some people. Even without an allergic reaction, an itchy scalp caused by the lice bites may make it difficult to sleep.

Head lice are not affected by hair hygiene. Daily shampooing will not prevent head lice or kill them. The lice are looking for human blood and don't care if hair is clean or dirty.

Head lice cannot jump or fly. They travel to another person's hair by head-to-head contact, or by contact with a hat or hair accessory that is infected. Preschool and elementary children and their families are most often affected. Girls are more likely to get head lice than boys. Head lice can affect people across the country and at all income levels.

Nits are head lice eggs. They are yellow or white ovals found within a quarter inch of the scalp firmly cemented to the hair shaft. Nits found farther up the hair shaft mean an old infestation. The eggs hatch in 8 days and then take another 8 days to mature into an adult able to lay more eggs. A female louse has a life span of about one month and lays 7 to 10 eggs a day. Nits are often confused with dandruff and other hair debris such as hair spray droplets. Adult head lice are the size of a sesame seed and tan to grayish-white in color.

Hot water will not kill lice. But water itself will slow head lice down, so wet hair will make it easier to comb them out. Special shampoos containing pesticides are available to kill nits and lice. But many lice have become resistant to the pesticide shampoos. These shampoos also pose a threat to kids by exposing them to toxic chemicals, especially when given again and again. You can use a nit-removal comb to remove the lice and nits by hand over a period of several days. Be sure to thoroughly clean the comb before using it again.

Experts used to recommend this procedure, but they now say it's not needed. Head lice die within 24 to 48 hours of leaving a human host, so any lice that may end up on clothing or toys will not survive. What is recommended is to wash any bed clothing, pillowcases, sheets, towels, and scarves in hot water, then dry them on a hot air cycle. Lice and eggs are killed after 5 minutes of exposure to temperatures greater than 128.3 degrees. (Make sure the items are able to withstand the high heat.) Items that can't be laundered may be sealed in a plastic bag for 2 weeks or dry-cleaned. You don't need to over-vacuum a house or to use insecticides in the home to rid it of lice. You should vacuum furniture, rugs, cars, and any stuffed animals not able to be put in the clothes dryer.

Besides hats, they also should not share combs, hairbrushes, hair accessories, or towels with friends. Pets and other animals don't get head lice and are not involved in passing them from one person to another. Your child cannot get head lice from a swimming pool, but could get them from infested towels. Tell your child not to use chairs, pillows, couches, or beds of a person with lice.