You are trying to load the Human Atlas. Either you do not have the newest version of Adobe Flash®, or you have JavaScript disabled, both of which are required to use this system.

Adjust Font Size
 
Search Health Information   
 
 
 
•Encyclopedia Home
•Diseases A-Z
•Read Spanish version
Images
Lice, head - nits in the hair with close-up
Lice, head - nit...
 
Read More
•Body lice
•Pubic lice
•Seborrheic dermatitis
More Features
•Printer-friendly version
 

Head lice

Definition

Head lice are tiny insects that live on the skin covering the top of your head (scalp). Head lice may also be found in eyebrows and eyelashes.

Lice can be spread by close contact with other people.

Alternative Names

Pediculosis capitis - head lice

Causes, incidence, and risk factors

Head lice infect hair on the head. Tiny eggs on the hair look like flakes of dandruff. However, instead of flaking off the scalp, they stay put.

Head lice can live up to 30 days on a human. Their eggs can live for more than 2 weeks.

Head lice spread easily, particularly among school children. Head lice are more common in close, overcrowded living conditions.

You can get head lice if you:

  • Come in close contact with a person who has lice
  • Touch the clothing or bedding of someone who has lice
  • Share hats, towels, brushes, or combs of someone who has had lice

Having head lice causes intense itching, but does not lead to serious medical problems. Unlike body lice,head lice never carry or spread diseases.

Having head lice does NOT mean the person has poor hygiene or low social status.


Symptoms

Symptoms of head lice include:
  • Very bad itching of the scalp
  • Small, red bumps on the scalp, neck, and shoulders (bumps may become crusty and ooze)
  • Tiny white specks (eggs, or nits) on the bottom of each hair that are hard to get off

Signs and tests

Head lice can be hard to see. You need to look closely. Use disposable gloves and look at the person's head under a bright light. Full sun or the brightest lights in your home during daylight hours work well. A magnifying glass can help.

To look for head lice:

  • Part the hair all the way down to the scalp in very small sections
  • Examine the scalp and hair for moving lice and eggs (nits).
  • Look at the whole head this way.
  • Look closely around the top of the neck and ears (the most common locations for eggs).

Both children and adults should be treated right away if any lice or eggs are found.

Treatment

Lotions and shampoos containing 1% permethrin (Nix) often work well. You can buy these medicines at the store without a prescription. If these products do not work, a doctor can give you a prescription for stronger medicine. Always use the medicines exactly as directed. Using them too often or in the wrong way can cause side effects.

To use the medicine shampoo:

  • Rinse and dry the hair.
  • Apply the medicine to the hair and scalp
  • Wait 10 minutes, then rinse it off.
  • Check for lice and nits again in 8 -12 hours.
  • If you find active lice, talk to your health care provider before doing another treatment.
You also need to get rid of the lice eggs (nits) to keep lice from coming back. To get rid of nits:
  • You can use products that make the nits easier to remove. Some dishwashing detergents can help dissolve the "glue" that makes the nits stick to the hair shaft.
  • Remove the eggs with a nit comb. Before doing this, rub olive oil in the hair or run the metal comb through beeswax. This helps make the nits easier to remove.
  • Metal combs with very fine teeth are stronger and work better than plastic nit combs. These metal combs are easier to find in pet stores or on the Internet.
  • Comb for nits again in 7 - 10 days.

When treating lice, wash all clothes and bed linens in hot water with detergent. This also helps prevent head lice from spreading to others during the short period when head lice can survive off the human body.

Ask your health care provider if people who share bedding or clothes with the person who has head lice need to be treated as well.

Expectations (prognosis)

Most of the time, lice are killed with the proper treatment. However, lice can come back if you do not get rid of them at the source.

Complications

Some people will develop a skin infection from scratching. Antihistamines can help ease itching. 

Calling your health care provider

Call your health care provider if:

  • You still have symptoms after home treatment.
  • you develop areas of red, tender skin, which could signal an infection.

Prevention

Never share hair brushes, combs, hair pieces, hats, bedding, towels, or clothing with someone who has head lice.

If your child has lice, be sure to check policies at schools and daycare. Many places do not allow infected children to be at school until the lice have been completely treated.

Some schools may have policies to make sure the environment is clear of lice. Cleaning of carpets and other surfaces often helps prevent spread of all types of infections, including head lice.

References

Morelli JG. Arthropod bites and infestations. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 660.

Elston DM. Arthropods and leeches. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 367.

Diaz JH. Lice (pediculosis). In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 293.

Burkhart CN, Burkhart CG, Morrell DS. Infestations. In: Bolognia JL, Jorizzo JL, Schaffer JV, et al, eds. Dermatology. 3rd ed. Philadelphia, Pa: Mosby Elsevier; 2012:chap 84.

Review Date: 2/21/2013
Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
adam.com