Head Lice

What Are Head Lice?

The head louse, or Pediculus humanus capitis, is a parasitic insect that can be found on the head, eyebrows, and eyelashes of people. Head lice feed on human blood several times a day and live close to the human scalp. Headlice are not known to spread disease.

How Did I Get Head Lice?

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 attached to shed hair hatch, and get on the shared clothing or belongings. Examples include sharing clothing (hats, scarves, coats, sports uniforms) or articles (combs, brushes, hair ribbons or barrettes, towels, stuffed animals) recently worn or used by an infested person; or 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 affect the spread of head lice.

How is Head Lice Infestation Diagnosed?

The diagnosis of a head lice infestation is best made by finding a live nymph or adult louse on the scalp or hair of a person. Because nymphs and adult lice are very small, move quickly, and avoid light, they can be difficult to find. Use of a magnifying lens and a fine-toothed comb may be helpful to find live lice. If crawling lice are not seen, finding nits firmly attached within a ¼ inch of base of the hair shafts strongly suggests, but does not confirm, that a person is infested and should be treated. Nits that are attached more than ¼ inch from the base of the hair shaft are almost always dead or already hatched. Nits are often confused with other things found in the hair such as dandruff, hair spray droplets, and dirt particles. If no live nymphs or adult lice are seen, and the only nits found are more than ¼-inch from the scalp, the infestation is probably old and no longer active and does not need to be treated. If you are not sure if you have head lice, a diagnosis could be made by your health care provider, local health department, or other person trained to identify live head lice.

Treatment

Requires using an over-the-counter (OTC) or prescription medication. Follow these treatment steps:

Before applying treatment, it may be helpful to remove clothing that can become wet or stained during treatment.
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.
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 medicine is removed. These measures may reduce the effectiveness of the medications.
Put on clean clothing after treatment.
If a few live lice are still found 8–12 hours after treatment, but are moving more slowly than before, do not re-treat. 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.
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 re-treat 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.
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.
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.
Re-treatment is meant to kill any surviving hatched lice before they produce new eggs. For some drugs, re-treatment 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.

Preventive Measures

Head lice do not survive long if they fall off a person and cannot feed. You don't need to spend a lot of time or money on housecleaning activities. Follow these steps to help avoid re–infestation by lice that have recently fallen off the hair or crawled onto clothing or furniture.

Avoid head-to-head (hair-to-hair) contact at home, school, and elsewhere.
Do not share clothing such as hats, scarves, coats, sports uniforms, hair ribbons, or barrettes.
Do not share combs, brushes, or towels. Disinfest combs and brushes used by an infested person by soaking them in hot water (at least 130°F) for 5–10 minutes.
Do not lie on beds, couches, pillows, carpets, or stuffed animals that have recently been in contact with an infested person.
Machine wash and dry clothing, bed linens, and other items that an 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 OR sealed in a plastic bag and stored for 2 weeks.
Vacuum the floor and furniture, particularly where the infested person sat or lay. However, spending much time and money on housecleaning activities is not necessary to avoid reinfestation by lice or nits that may have fallen off the head or crawled onto furniture or clothing.
Do not use fumigant sprays or fogs; they are not necessary to control head lice and can be toxic if inhaled or absorbed through the skin.