About Pediculus humanus capitis (Head Lice)

Head lice infestation, or pediculosis, are mainly spread by direct contact with the hair of an infested person. Head lice infest the head and neck and attach their eggs, or nits, to the base of the hair shaft. Lice move by crawling; they cannot hop or fly.  Adult head lice are roughly 2-3 mm long.

How is it transmitted?

Head-to-head contact with an already infested person is the most common way to get head lice. Although uncommon, head lice can be spread by sharing clothing or belongings. This happens when lice crawl, or nits (e.g. eggs) attached to shed hair hatch, and get on the shared clothing or belongings.

Examples include:

  • sharing clothing (hats, scarves, coats, sports uniforms) or articles (hair ribbons, barrettes, combs, brushes, towels, stuffed animals) recently worn or used by an infested person;


  • lying on a bed, couch, pillow, or carpet that has recently been in contact with an infested person.

Dogs, cats, and other pets do not play a role in the transmission of human lice.

Signs and Symptoms

Signs of head lice may include a tickling feeling or something moving in the hair; itching, caused by an allergic reaction to the bites of the head louse; irritability and difficulty sleeping because head lice are most active in the dark; sores on the head caused by scratching.


Over-the-counter and prescription medications are available for treatment of head lice infestations. Treatments for head lice are generally safe and effective when used correctly. Some treatments may cause itching or a mild burning sensation caused by inflammation of the skin on the scalp. Most products used to treat head lice are pesticides that can be absorbed through the skin. All medicines used for the treatment of lice should be used with care and only as directed.

Supplemental treatment

Head lice do not survive long if they fall off a person. Follow these steps to help avoid re-infestation by lice that have recently fallen off the hair or crawled onto clothing or furniture.

  1. Machine wash and dry clothing, bed linens, and other items that the infested person wore or used during the 2 days before treatment using the hot water (130°F) laundry cycle and the high heat drying cycle. Clothing and items that are not washable can be dry-cleaned


  1. Seal clothing, bed linens, and other items the infested person wore in a plastic bag and store for 2 weeks.
  2. Soak combs and brushes in hot water (at least 130°F) for 5-10 minutes.
  3. Vacuum the floor and furniture, particularly where the infested person sat or lay.
    1. The risk of getting infested by a louse that has fallen onto a rug or carpet or furniture is very low. Head lice survive less than 1-2 days if they fall off a person and cannot feed; nits cannot hatch and usually die within a week if they are not kept at the same temperature as that found close to the human scalp.
  4. Do not use fumigant sprays; they can be toxic if inhaled or absorbed through the skin.


All household members and other close contacts should be checked for nits or lice (see Removal Experts below); those persons with evidence of an active infestation should be treated. All infested persons, household members, close contacts, and bedmates should be treated at the same time.

How to use an Over-the-counter (OTC) or prescription medication.

  1. Before applying treatment, remove clothing that can become wet or stained during treatment.
  2. Apply lice medicine, also called pediculicide, according to the instructions contained in the box or printed on the label. If the infested person has very long hair (longer than shoulder length), it may be necessary to use a second bottle. Pay special attention to instructions on the label or in the box regarding how long the medication should be left on the hair and how it should be washed out.

WARNING: Do not use a combination shampoo/conditioner, or conditioner before using lice medicine. Do not re-wash the hair for 1-2 days after the lice medicine is removed. These measures may reduce the effectiveness of the lice medications.

  1. Put on clean clothing after treatment.
  2. If a few live lice are still found 8-12 hours after treatment, but are moving more slowly than before, do not retreat. The medicine may take longer to kill all the lice. Comb dead and any remaining live lice out of the hair using a fine-toothed nit comb.
  3. If, after 8-12 hours of treatment, no dead lice are found and lice seem as active as before, the medicine may not be working. Do not retreat until speaking with your health care provider; a different pediculicide may be necessary. If your health care provider recommends a different pediculicide, carefully follow the treatment instructions contained in the box or printed on the label.
  4. Nit (head lice egg) combs, often found in lice medicine packages, should be used to comb nits and lice from the hair shaft. Many flea combs made for cats and dogs are also effective.
  5. After each treatment, checking the hair and combing with a nit comb to remove nits and lice every 2-3 days may decrease the chance of self-reinfestation. Continue to check for 2-3 weeks to be sure all lice and nits are gone. Nit removal is not needed when treating with spinosad topical suspension.
  6. Retreatment is meant to kill any surviving hatched lice before they produce new eggs. For some drugs, retreatment is recommended routinely about a week after the first treatment (7-9 days, depending on the drug) and for others only if crawling lice are seen during this period. Retreatment with lindane shampoo is not recommended.

Lice Removal Experts:

Center for Lice Control   610-557-1188

Lice Doctors 800-224-2537

Lice Happens  610-952-3691

Lice Ladies Spa  215-346-6446

Lice Lifters 484-685-1095

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(updated 11/12/2015)