Lice feed on human blood and can be found on the human head, body and pubic area. The female louse produces a sticky substance that firmly attaches each egg to the base of a hair shaft. Eggs hatch in 6 to 9 days.

You can get lice by coming into contact with either lice or their eggs. Lice can't jump or fly. They spread through:

• Head-to-head or body-to-body contact. This may occur as children or family members play or interact closely.
• Closely stored belongings. Storing clothing that have lice close together in closets, lockers or on side-by-side hooks at school can spread lice. Lice also can spread when storing personal items such as pillows, blankets, combs and stuffed toys together.
• Items shared among friends or family members. These may include clothing, headphones, brushes, combs, hair accessories, towels, blankets, pillows and stuffed toys.
• Contact with furniture that has lice on it. Lying on a bed or sitting in overstuffed, cloth-covered furniture recently used by someone with lice can spread them. Lice can live for 1 to 2 days off the body.
• Sexual contact. Pubic lice usually spread through sexual contact. Pubic lice most commonly affect adults. Pubic lice found on children may be a sign of sexual exposure or abuse.

It's difficult to prevent the spread of head lice among children in child care and school settings. There's so much close contact among children and their belongings that lice can spread easily. The presence of head lice isn't a reflection of hygiene habits. It's also not a failure on the parent if a child gets head lice.

Some nonprescription products claim to repel lice. But more research is needed to prove their safety and effectiveness.

Many small studies have shown that ingredients in some of these products — mostly plant oils such as coconut, olive, rosemary and tea tree — may work to repel lice. However, these products are classified as "natural," so they aren't regulated by the Food and Drug Administration (FDA). Their safety and effectiveness haven't been tested to FDA standards.

Until more research proves the effectiveness of head lice prevention products, the best approach is simply to take thorough steps to get rid of lice and their eggs if you find them on your child. In the meantime, these steps can help prevent lice:

• Ask your child to avoid head-to-head contact with classmates during play and other activities.
• Teach your child not to share personal belongings such as hats, scarves, coats, combs, brushes, hair accessories and headphones.
• Tell your child to avoid shared spaces where hats and clothing from more than one student are hung on a common hook or kept in a locker.

However, it's not realistic to expect that you and your child can avoid all contact that may cause the spread of lice.

Your child may have nits in his or her hair but may not develop a case of head lice. Some nits are empty eggs. However, nits that are found within 1/4 inch (6 millimeters) of the scalp typically should be treated — even if you find only one — to prevent the possibility of hatching.

During an exam, a health care provider may use a magnifying lens to look for lice. The provider may also use a special light, called a Wood's light, to check for nits. This light makes the nits easier to spot by making them look pale blue.

Head lice

A health care provider may diagnose head lice after finding a live young or adult louse in the person's hair or on the scalp, or after seeing one or more nits on hair shafts found within 1/4 inch (6 millimeters) of the scalp.

Body lice

A health care provider may diagnose body lice if they find eggs or crawling lice in clothing seams or on bedding. You can see a body louse on skin if it crawls there to feed.

Pubic lice

A health care provider may diagnose pubic lice when they see moving lice or nits on hair in the pubic area or on other areas of coarse hair, such as chest hair, eyebrows or eyelashes.

Use drugs that treat lice only as directed. Applying too much can cause red, irritated skin.

Head lice

Head lice treatment may involve:

• Nonprescription products. Shampoos containing permethrin (Nix) are usually the first option used to combat lice. Permethrin is a synthetic version of pyrethrin, which is a chemical compound extracted from the chrysanthemum flower. Permethrin is toxic to lice. Follow the directions closely when using this product.

  A lotion containing ivermectin (Sklice) also is available without a prescription. Ivermectin is toxic to lice. The lotion is approved for use in adults and children age 6 months or older. You can apply it once to dry hair and then rinse with water after 10 minutes.

  Don't repeat the ivermectin treatment without talking to your health care provider first. Possible side effects include eye irritation or redness, dandruff, dry skin, and a burning sensation at the application site.

  In some locations, lice have grown resistant to the ingredients in nonprescription treatments. If nonprescription treatments don't work, your health care provider can prescribe shampoos or lotions that contain different ingredients.

• Oral prescription drug. Ivermectin (Stromectol) is available by prescription as a tablet taken by mouth. The oral drug effectively treats lice with two doses, eight days apart. This drug is typically used when other treatments haven't been effective.

  Children must weigh at least 33 pounds (15 kilograms) to take oral ivermectin. Side effects may include nausea and vomiting.

• Topical prescription drugs. Malathion is a prescription drug that you apply to the hair and then rub into the hair and scalp. Malathion has a high alcohol content and is flammable. So keep it away from heat sources such as hair dryers, electric curlers and cigarettes.

  If you're pregnant or breastfeeding, talk to your health care provider before using this drug. The drug isn't recommended for children 2 and under. It's not clear if it's safe for use in 2- to 6-year-olds.

  Spinosad (Natroba) is a newer prescription treatment for head lice. You can apply it to dry hair and the scalp for 10 minutes and then rinse with water. The treatment doesn't usually need to be repeated. But it can be used again after seven days if live lice are still present.

  Possible side effects of spinosad include redness or irritation of the eyes and skin. This drug isn't recommended for children younger than age 4.

Body lice

If you have body lice, first bathe with soap and water. After bathing, apply permethrin (Nix) to the affected areas before bedtime and then shower in the morning. Repeat this treatment nine days after the first application.

Also take other measures to get rid of body lice. Wash clothing and bedding with hot, soapy water — at least 130 F (54 C) — and dry them at high heat for at least 20 minutes. Vacuum the floors and furniture. And seal unwashable items in an airtight bag for two weeks.

Pubic lice

Pubic lice can be treated with many of the same nonprescription and prescription treatments used for head lice. Carefully follow the package instructions. Talk to your health care provider about treatment of lice and nits on eyebrows or eyelashes.

Self-care

Whether you use nonprescription or prescription shampoo to kill lice, much of the treatment involves self-care steps you can take at home. These include making sure all the nits are removed and that all clothing, bedding, personal items and furniture are free of lice.

In most cases, killing lice that are on you isn't difficult. The challenge is getting rid of all the nits and avoiding contact with other lice at home or school.

You can get rid of lice with a patient, detailed approach that involves cleaning yourself or your child and any personal belongings that may contain lice.

These steps may help you get rid of lice:

• Check other household members for lice and nits. Treat anyone who has signs of lice.

• Use lotions and shampoos. Choose from among several nonprescription lotions and shampoos designed to kill lice. Apply the product according to package instructions.

  You may need to repeat treatment with the lotion or shampoo in about 9 to 10 days after the first application. Be sure to check the age recommendations of the drugs before using them on children.

• Comb wet hair. Use a fine-toothed or nit comb to physically remove the lice from wet hair. Repeat every 3 to 4 days for at least two weeks. This method may be used in combination with other treatments. It is usually recommended as the first line treatment for infants younger than 2 months.
• Wash items. Wash bedding, stuffed animals, clothing and hats with hot, soapy water — at least 130 F (54 C) — and dry them at high heat for at least 20 minutes.
• Seal unwashable items. Place them in an airtight bag for two weeks.
• Vacuum. Vacuum the floor and furniture well.
• Wash combs and brushes. Use very hot, soapy water — at least 130 F (54 C) — or soak combs and brushes in rubbing alcohol for an hour.

One thing you don't need to worry about is your household pets. Lice prefer people to pets. So your pets don't need any treatment for lice.

Many home or natural remedies, such as mayonnaise or olive oil, are used to treat head lice. But there's little to no evidence of their effectiveness.

A special machine that uses hot air to dehydrate head lice and their eggs is another alternative treatment method. The machine requires special training and is currently available only at professional lice treatment centers.

A regular hair dryer can't be used to do this at home because it's too hot and could burn the scalp. The machine that dehydrates lice is cooler than most hair dryers but has a much higher flow rate to kill the lice by drying them out.

Often, you can get rid of lice with nonprescription treatments and by properly washing household items that had lice on them, such as sheets, towels and clothes. If these steps don't work, see your health care provider.

Here's some information to help you get ready for your appointment and what to expect from your provider.

What you can do

• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including when you might have been exposed to lice, whom you might have exposed and what household items might be contaminated.
• Make a list of all medications, vitamins or supplements that you're taking.
• Write down questions to ask your health care provider. Your time with your provider is limited, so preparing a list of questions ahead of time will help you make the most of your time together. List your questions from most important to least important in case time runs out.

Some basic questions to ask your health care provider about lice include:

• How do I treat lice?
• Is there a generic alternative to the medicine you're prescribing?
• How often can I safely use this product?
• How do I get rid of lice from household items?
• Who do I need to inform about my condition?
• What other actions do I need to take to avoid getting lice again or giving it to others?
• Are there any brochures or other printed material that I can take home with me? What websites do you recommend?
• Should I plan for a follow-up visit?

In addition to the questions that you've prepared to ask your health care provider, don't hesitate to ask questions during your appointment when you don't understand something.

What to expect from your doctor

Your health care provider is likely to ask you a number of questions, such as:

• When did you first begin experiencing symptoms?
• How were you exposed to lice?
• Is there anyone you might have exposed to lice?
• How severe are your symptoms?

What you can do in the meantime

If you think or know you have lice, avoid sharing personal items, bedding, towels or clothing. Bathe and follow self-care measures, including washing items in hot water.

If you think or know you have pubic lice, also avoid sexual activity until you've been treated.