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10 Things to Know About Head Lice

Doctor William C Lloyd Healthgrades Medical Reviewer
Medically Reviewed By William C. Lloyd III, MD, FACS
Written By Cindy Kuzma on June 27, 2021
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    What to Know About Head Lice
    They hide from the light. They feed on your blood. No, they're not the villains in the latest vampire flick—they're head lice. These tiny creatures, about the size of a sesame seed, don't cause lasting damage or carry any diseases. Still, most of us would rather skip an itchy, annoying infestation.
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    1. Lice Love Humans
    Head lice have claws specially designed to cling to human hair. To survive, they huddle close to your scalp, eating blood several times a day. A single bug, called a louse, can live up to 30 days on your head but dies within a day or two if it falls off.
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    2. Children and Adults Can Get Them
    Head lice infest younger children in child care or school first because they play closely together. An estimated 6 million to 12 million cases occur each year among kids ages 3 to 11. But adults can get head lice, too. If one child in your house is infested, it's best to check everyone.
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    3. They're Not a Sign of Poor Hygiene
    Head lice spread through direct head-to-head contact. For kids, this often occurs at school, sports activities, camp, or slumber parties. Less commonly, lice travel on hats, scarves, coats, brushes, or combs. The cleanliness of your hair, home, or school has nothing to do with the risk of getting them.
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    4. They're Sometimes Mistaken for Dandruff
    Nits are head lice eggs, and they're small, oval-shaped, and tough to spot. People who detect them often think they're dandruff, scabs, or droplets of hairspray. If they're not treated, they'll hatch into nymphs, or young lice, within eight to nine days. Within about another seven days, they'll become adult lice.
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    5. Poor Sleep Is One Symptom
    Head lice are most active in the dark. Itchiness often keeps affected people awake. Other symptoms include tickling on the head, itching from an allergic reaction to bites, and developing sores from scratching. You might also see lice on your or your child's scalp, eyebrows, or eyelashes.
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    6. Diagnosis Can Be Tricky
    The best way to confirm an infestation is to find a live louse. Use a magnifying glass and a fine-toothed comb to search. Nits more than a quarter-inch from the scalp are almost always dead, and usually the infestation no longer needs treatment. If you're unsure, ask a doctor or health department official.
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    7. Over-the-Counter Products May Solve the Problem
    Some medicated shampoos and creams are available without a prescription. Called pediculicides, many contain the ingredients pyrethrin (such as the brand Rid) or permethrin (Nix). Read the instructions carefully. Ask your doctor before using them if you're pregnant or if you or your child has allergies or asthma.
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    8. Your Doctor Can Also Prescribe Treatments
    Prescription-strength creams, lotions, and shampoos kill lice when milder products can't. Some may be safer for pregnant or breast-feeding women. These treatments may contain the ingredients ivermectin (Sklice) or benzyl alcohol (Ulesfia). Some may require the use of a fine-toothed nit comb after each application to remove remaining nits.
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    9. Skip the Home Remedies
    There's no proof mayonnaise, olive oil, margarine, or butter kills lice. However, nondrug methods can supplement pesticide treatment. Wash clothing, linens, combs, and brushes with hot water. Vacuum floors and furniture. But don't spend too much time or money; lice can't live long if they're not on a human host.
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    10. Check Your School's Policy
    Most elementary and grade schools have rules regarding head lice infestations. For instance, some don't allow infected children at school until they're free of nits. To prevent the spread of lice, tell children to avoid contact with the hair of infected friends or classmates.
10 Things to Know About Head Lice
  1. Head Lice, American Academy of Family Physicians, Dec. 10, 2010 (http://familydoctor.org/familydoctor/en/diseases-conditions/head-lice.printerview.all.html);
  2. Drugs@FDA: Sklice, U.S. Food and Drug Administration (http://www.accessdata.fda.gov/scripts/cder/drugsatfda/index.cfm?fuseaction=Search.DrugDetails);
  3. Biology, Centers for Disease Control and Prevention, Nov. 2, 2010 (http://www.cdc.gov/parasites/lice/head/biology.html);
  4. Frequently Asked Questions (FAQs), Centers for Disease Control and Prevention, November 2, 2010 (http://www.cdc.gov/parasites/lice/head/gen_info/faqs.html);
  5. Treatment Frequently Asked Questions (FAQs), Centers for Disease Control and Prevention, November 2, 2010 (http://www.cdc.gov/parasites/lice/head/gen_info/faqs_treat.html);
  6. Prevention & Control, Centers for Disease Control and Prevention, November 2, 2010 (http://www.cdc.gov/parasites/lice/head/prevent.html);
  7. Treatment: General Guidelines, Centers for Disease Control and Prevention, November 2, 2010 (http://www.cdc.gov/parasites/lice/head/treatment.html);
  8. Treating Head Lice, U.S. Food and Drug Administration, April 16, 2012 (http://www.fda.gov/forconsumers/consumerupdates/ucm171730.htm);
  9. Contagious Health Problems in Schools, American Academy of Pediatrics, Dec. 30, 2011 (http://www.healthychildren.org/English/ages-stages/gradeschool/school/pages/Contagious-Health-Proble...;
  10. Malathion Topical, U.S. National Library of Medicine and the National Institutes of Health, Feb. 15, 2012 (http://www.nlm.nih.gov/medlineplus/druginfo/meds/a611010.html);
  11. Benzyl Alcohol Topical, U.S. National Library of Medicine and the National Institutes of Health, Feb. 15, 2012 (http://www.nlm.nih.gov/medlineplus/druginfo/meds/a611011.html);
  12. Head Lice, U.S. National Library of Medicine and the National Institutes of Health, Feb. 1, 2012 (http://www.nlm.nih.gov/medlineplus/ency/article/000840.htm);
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Last Review Date: 2021 Jun 27