Mayo Clinic Health Library

Head lice

Updated: 06-01-2011

Definition

Head lice are a very common problem, affecting millions of people each year — especially preschool and elementary school-aged children and their close contacts. Head lice are tiny, wingless, parasitic insects that live and feed on blood from your scalp.

Getting head lice isn't a sign of bad personal hygiene or an unclean living environment. This itchy infestation, also called pediculosis capitis, most commonly spreads through close personal contact and by sharing personal belongings.

Both over-the-counter and prescription medications are available to treat head lice. Following the directions properly and taking necessary steps at home are important to prevent head lice from recurring.

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Symptoms

Common signs and symptoms of head lice may include:

  • Intense itching. An allergic reaction to the saliva that lice inject during feeding may result in itchy red bumps on your scalp, neck and shoulders. Some people, particularly if this is their first infestation, don't experience itching.
  • Adult lice on scalp. The most common spots to find adult lice are behind your ears and along the back of your neck. Lice are tiny, about the size of a strawberry seed, but they can be up to 1/8 inch (3 millimeters) in size.
  • Lice eggs (nits) on hair shafts. Nits resemble tiny pussy willow buds. Nits can be mistaken for dandruff, but unlike dandruff, they can't be easily brushed out of hair.

When to see a doctor
Usually you can get rid of lice by using nonprescription shampoo that's specifically formulated to kill lice. However, if nonprescription shampoo doesn't kill the lice, your doctor can prescribe a stronger, prescription shampoo.

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Causes

Head lice can't fly or jump, and they're not transmitted by pets. They spread by head-to-head contact or via contact with contaminated personal belongings or home furnishings.

Head-to-head contact
This is the most common mode of transmission and may occur as children or family members play or interact closely together.

Sharing personal items
Less commonly, head lice may be transmitted via such items as:

  • Caps, hats and scarves
  • Brushes and combs
  • Hair decorations, such as barrettes
  • Headphones

Home furnishings
Head lice may sometimes be contracted by contact with contaminated:

  • Towels
  • Clothing
  • Blankets
  • Pillows
  • Upholstered furniture
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Risk factors

The greatest risk factor for getting head lice is coming into contact with someone who already has lice. Cleanliness and personal hygiene have little bearing on whether you get lice.

Young children, preschool through elementary age, are most prone to infestation, which often transfers to a child's family members. Females of all ages get head lice more often than males do.

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Complications

Lice may cause you to scratch your head so vigorously that you break the skin. See your doctor if these scratches become infected.

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Preparing for your appointment

In most cases, you don't need to see a doctor for head lice. But you may want to consult your family physician if:

  • You need help determining if you or your child has been infected
  • Over-the-counter lice treatments aren't working

What you can do
You may want to write a list that includes:

  • Detailed descriptions of the symptoms
  • Information about past medical problems
  • Questions you want to ask the doctor

For head lice, questions you may want to ask your doctor include:

  • How do you treat head lice?
  • Is there an over-the-counter or generic alternative to the medicine you're prescribing me?
  • How do I rid household items of head lice?
  • Who do I need to inform about my or my child's condition?
  • What other measures do I need to take to avoid re-infestation?
  • Do you have 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 doctor, don't hesitate to ask questions during your appointment if you don't understand something.

What to expect from your doctor
Your doctor will check your head for lice and your hair for nits. He or she may use a special light, called a Wood's light, which makes the nits look pale blue.

Your doctor also may ask you a number of questions, such as:

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

What you can do in the meantime
If you or your child has head lice, avoid sharing personal items, bedding, towels or clothing. Use an over-the-counter treatment for head lice or try a wet-combing technique for your hair or your child's hair to physically remove lice and nits. Rid personal items, such as clothing or bedding, by washing them in very hot water or sealing them in plastic bags for several days.

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Tests and diagnosis

Lice cement their eggs firmly onto the base of hair shafts, very close to the scalp. According to experts with the Centers for Disease Control and Prevention, nits found more than a quarter of an inch (6.5 millimeters) away from the scalp have either already hatched or aren't going to hatch. So simply finding nits isn't proof of an active infestation. The clearest sign is finding a living, moving louse. Combing wet hair with a fine-toothed comb is the best way to find this evidence.

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Treatments and drugs

Over-the-counter products
Shampoos containing either pyrethrin (Rid, others) or permethrin (Nix) are usually the first option used to combat lice infestations. These work best if you follow the directions very closely.

In some geographical locations, lice have grown resistant to the ingredients in over-the-counter lice treatments. If over-the-counter preparations don't work, your doctor can prescribe shampoos or lotions that contain different ingredients.

Prescription medications

  • Malathion (Ovide). Malathion is intended for use in adults and children age 6 or older. You apply malathion to your hair, and then rub it into your hair and scalp. This medication is flammable, so keep it away from heat sources, such as hair dryers, electric curlers and cigarettes. If you're pregnant or breast-feeding, talk to your doctor before using this product, because the medicine could affect your baby.
  • Lindane. This prescription medication is available as a cream, lotion or shampoo. Your doctor may not recommend using lindane if you weigh less than 110 pounds (49.9 kilograms); are pregnant or breast-feeding; have seizures; or have HIV infection. Side effects may include skin irritation and seizures.
  • Benzyl alcohol lotion. This newer treatment should not be used in children younger than 6 months. Side effects may include irritations of the skin, scalp and eyes. According to the Food and Drug Administration, serious side effects — such as seizures, coma or death — may occur if this product is used on premature infants.

Combing wet hair
If you don't want to employ insecticides, a fine-toothed or nit comb can physically remove the lice from wet hair. Repeat every three to four days for at least two weeks. This method is recommended as the first line treatment for children under age 2.

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Lifestyle and home remedies

Lice can live for about two days without a meal, and nits will die within a week if they're not kept at the same temperature as that found near the human scalp. That's why it's so uncommon for people to be infected with lice by any method other than head-to-head contact. All close contacts need to be examined. Despite this low risk, you may want to: 

  • Wash items in hot water. Wash bedding, stuffed animals, clothing and hats with hot, soapy water — at least 130 F (54.4 C) — and dry them at high heat for at least 20 minutes. Soak brushes and combs in very hot water for five to 10 minutes.
  • Seal items in plastic bags. Place bedding, clothing and unwashable items in an airtight bag for three to four days. This will kill live lice, and newly hatched lice will die because they have no nutrition.
  • Vacuum. Give the floor and furniture a good vacuuming.
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Prevention

It's difficult to prevent the spread of head lice among children in child care and in school. There's so much close contact among children and their belongings that lice can spread easily. It's no reflection on your hygiene habits or those of your children, and it's not a failure on your part as a parent if your child gets head lice.

You can ask your child not to share hats, scarves, coats, combs, brushes, hair decorations and other personal belongings at school. But it's not realistic to expect that you and your child can eliminate all the types of contact that may result in the spread of lice.

The best approach to head lice prevention is simply to take thorough steps to get rid of the lice — and their eggs — so that you don't have more lice to deal with.

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