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Common Infections

Head Lice

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What Are Lice?

The head louse is a tiny, wingless insect that lives among human hairs and feeds on extremely small amounts of blood. Lice (the plural of louse) are a very common problem. Kids are most likely to get lice, but teens can get them too.

Lice aren’t dangerous. They don’t spread disease. But they are contagious, so they can spread from person to person easily. They’re also annoying: louse bites can itch. If someone scratches a lot, it may lead to skin irritation and even infection.

A head louse can survive up to 4 weeks on a person’s head and lay 10 eggs a day. Since that means lice can multiply fast, it’s a good idea to treat head lice quickly.

louse and nit illustration

Signs of Lice

Lice are tiny, but you can still see them — though it’s not always easy. An adult louse is grayish white or tan and about the size of a small sesame seed. Lice move fast, so you’re actually more likely to see their eggs than the lice themselves.

Louse eggs are called nits. Nits look sort of like dandruff, except they don’t brush or fall off as easily as dandruff. Lice attach their nits to pieces of hair, close to the scalp. If you think you have lice and see a small, oval blob on a strand of hair, it’s probably a nit.

If nits are yellow, tan, or brown, it means the lice haven’t hatched yet. If the nits are white or clear, the lice have hatched and just the egg remains. Lice eggs hatch within 1 to 2 weeks after they’re laid.

Besides seeing nits or lice on the head, itching — or the feeling of something moving around on the scalp — is another clue that you might have lice. Like mosquito bites, the itching is a reaction to the saliva of the insect. Some people with lice also get a rash of small red bumps from scratching.

How They Spread

Lice cannot jump or fly. They spread from person to person when people’s heads touch or after sharing things like hats and other clothing, combs, brushes, headbands, or barrettes. Lice can live up to 2 days without feeding on a person, so you also can get lice from pillowcases, sheets, blankets, sleeping bags, and other bedding.

Lice have nothing to do with personal hygiene. Lice love everyone, including the cleanest kid in the class! Lice spread in schools and other group settings (like camp or even slumber parties) because these are places where people are in close contact. One reason why kids get lice more often than teens is because kids play together closely and often share more stuff.

You can’t get lice from a pet. Lice are “species specific,” meaning that people can’t catch lice from pets and pets can’t catch the kind of head lice that people get.

If You Think You Have Lice

If you think you have lice, call your doctor. Your doctor can recommend a medicated shampoo, cream rinse, or lotion to kill the lice. These may be over-the-counter (OTC) or prescription treatments. It all depends on what your doctor thinks will work best for you.

Lice can be hard to get rid of. If you still have lice 2 weeks after you started treatment, let your doctor know. Your doctor may want to try a different medication or repeat treatment in case any nits were left behind and hatched after treatment.

Lice are insects, so the treatments for lice are basically insecticides or pesticides. To avoid getting overexposed, you’ll need to follow the directions carefully when it comes to how much to use and how often to use it. Medicated lice treatments usually kill the lice and nits, but it may take a few days for the itching to stop.

As an alternative to chemical treatments, your doctor may recommend wet combing — using a fine-tooth comb on wet hair to remove nits and lice. You may have heard that petroleum jelly, mayonnaise, or olive oil can suffocate head lice, but these treatments may not be effective.

If you choose to get rid of lice without using medicine, talk to your doctor to decide on the best way. You’ll need to remove lice and nits carefully each week, for at least 3 weeks in a row. Watch for any live lice and take action if you see them.

Scratching a lot can lead to a scalp infection. Call your doctor as soon as possible if:

  • the skin on your scalp is red and tender
  • your scalp has crusting and oozing
  • you have swollen lymph glands

Your doctor may want to treat an infection with antibiotics.

If your doctor says you have lice or nits, call your school to let them know and stay home. Most schools allow students to return after one topical treatment has been completed, but your school will let you know what its policy is.

What Not to Do

When treating lice, there are a few things you should not do:

  • Don’t use a hairdryer after applying scalp treatments. Some treatments for lice contain flammable ingredients and you don’t want to set your hair on fire!
  • Don’t use conditioners or a shampoo/conditioner combination before putting on lice medication.
  • Don’t wash your hair for 1 to 2 days after using a medicated treatment.
  • Don’t use pesticide sprays or hire a pest control company to try to get rid of the lice; these can be harmful.
  • Don’t use more than one head lice medication at a time.

Preventing Lice

Lice can be tricky to get rid of because nits can remain unhatched on your head or you might pick up lice that are still on bedding or other items. Here’s what to do if you’ve had lice — or someone in your family has:

  • Wash bed linens and clothing that anyone with lice has used recently. Use very hot water (130ºF [54.4ºC]), then use the hot cycle of the dryer for at least 20 minutes.
  • Take items that can’t be washed (like comforters, pillows, clothing, and stuffed animals) to the dry cleaner. Or put them in airtight bags for at least 3 days.
  • Vacuum carpets and any upholstered furniture, as well as car seats, then throw away the vacuum cleaner bag.
  • Soak hair-care items like combs, barrettes, hair ties or bands, headbands, and brushes in rubbing alcohol or medicated shampoo for 1 hour. You also can wash them in hot water or just throw them away.
  • Because lice can move easily from person to person in the same house, family members will also need treatment to prevent the lice from coming back.

Here are some ways to avoid getting lice in the first place:

  • Try to avoid head-to-head contact, like in gym or during sports.
  • Don’t share combs, brushes, hats, scarves, bandanas, ribbons, barrettes, hair ties or bands, towels, helmets, or other personal care items with anyone else.
  • Don’t lie on bedding, pillows, and carpets that someone with lice has used in the past couple of days.
  • If someone in your family or at school has lice, ask a parent or adult to check your hair and scalp every 3 or 4 days to be sure you haven’t picked up lice.

Reviewed by: Rupal Christine Gupta, MD
Date reviewed: May 2015