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Posts for category: Head Lice

By Angelica Espinosa-Louissaint, M.D.
June 03, 2013
Category: Head Lice
Tags: Lice   Head Lice  

Head lice or pediculosis humanis capitis are tiny stubborn unpleasant parasites that live on the human scalp. Infestations are most common in preschool and school aged children between 3 and 11 years old.  Lice feed on blood and complete their life cycle while attached to human hosts. Lice infestation while very annoying to those affected, their families and schools are otherwise not dangerous. Head lice do not carry or spread diseases. Lice can be found on scalp hair eyelashes and eyebrows. They are usually present in adults, nymphs- newly hatched immature lice, and nits or eggs.


Head lice infestation is not related to hygiene or socioeconomic status.  Head lice spread easily especially among young children.  Lice do not jump or fly, they crawl and thus you can get head lice if you:

- Come in close (head to head) contact with a person that has lice

- Touch clothing or bedding of someone that has lice

- Share hats towels combs or brushes of someone who has lice

- Pets including dogs and cats DO NOT play a role in the spread of lice


Lice can live on a human scalp for 30 days and their eggs can live for 2 weeks.  However without a human host lice cannot survive more than 1-2 days  Nits cannot hatch if not attached close to the scalp , and will not survive a week if falls off a host.


Symptoms of lice include:

- Tickling moving feeling of something on scalp

- Intense itching  from allergic reaction to bites as lice feed

- Trouble sleeping secondary to itch as lice are most active in the dark



- Careful examination of the scalp using disposable gloves, bright light, magnifying glass, and a fine  tooth comb

- Seeing active live lice most commonly at the hairline at the neck and behind the ears

-Adult lice are about the size of a sesame seed and are gray-white in color

- Seeing nits/eggs attached about a 1/4 of an inch from the scalp or closer

- Nits can look like dandruff but a major difference is that they are glued on tightly to the hair shaft and do not flake off

- Nits found farther from scalp likely represent casings from newly hatched lice


Treatment is recommended even if only a few nits are found very close to the scalp.

If you are unsure if your child has lice see your pediatrician.

Who to treat?

Treatment is recommended for anyone with active infestation, as well as bedmates/close contacts of those individuals.


General guidelines for treatment:

These are recommendations for how to approach treatment regardless of what agent you may be using.

1) Remove any clothing you do not want to become wet or stained in the application process

2) Review directions for the application of the lice medicine  before beginning the process- some agents need to be applied to dry hair , others can be applied to rinsed or washed hair. DO NOT use conditioner or combo shampoo/conditioner products before application of medicine. These products can make the medicine less effective.

DO NOT re-wash hair for 1-2 days after lice medicine rinsed out as it is still working to treat infestation.

If the infested person has hair below shoulder length extra product may be required.

Pay special attention to how long medication should be left on the hair-this helps to minimize side effects and maximize efficacy.

3) Change into clean clothes after treatment

4) Check for lice activity 12 hrs after treatment. If no live lice seen or lice are moving slower than before do not re-treat. Use fine tooth comb to remove dead lice and nits.

Metal fine tooth combs found at pet stores or online are effective

5) Check scalp and comb to remove nits and lice every 2 days for 2-3 weeks to prevent re-infestation.

6) Re-treatment is recommended for most prescription and non-prescription agents at day 9. Most treatments are pediculocidal (kill lice) but not ovicidal (don't kill nits/eggs), so the second application is to kill any newly hatched lice before they mature and can lay new eggs.

7) Head lice do not survive long if they fall off a person and cannot feed. However to avoid reinfestation by lice that have recently fallen off hair or crawled on to bedding or furniture follow these steps:

        - Wash all bedding and clothing used by someone who has lice for the previous 2 days before treated on hot water cycle and high heat cycle for drying.

        - Items not washable can be dry-cleaned or, stored in a sealed plastic bag for 2 weeks.

        - Soak combs and brushes in hot water at least 130 deg F for 10 minutes.

        - Vacuum the floor/carpet /furniture  particularly where the infested person sat or lay. Risk of infestation by lice or nits on carpets or furniture is very low. It is not necessary to invest a lot of money or time in house cleaning or fumigation.





Treatment Options:

There are several over the counter and prescription options for lice treatment that are FDA approved.  First line treatments are OTC medications containing active ingredients pyrethrin such as in Pronto or RID, and permethrin 1% as in Nix. Pyrethrin is a natural extract of chrysanthemum and is safe and effective when used as directed but should be avoided by those allergic to chrysanthemums or ragweed. Permethrin is a synthetic version  of pyrethrin. Both products kill lice but not the nits, so have to be reapplied at day 9 to  kill any newly hatched lice. Pyrethrin can be used on children 2years and older, permethrin can be used as young as 2 months of age.


If after a full course of treatment live lice are still present there may be some resistance and you should contact your pediatrician.

Prescription options for treatment include Benzyl alcohol (Ulesfia), Malathione 0.5% (Ovide),and Ivermectin (Sklice). 


Malathione or Ovide is an organic pesticide considered safe for persons 6 years of age and older if used as directed . It is effective in killing live lice and is partially ovicidal. It is a flammable compound no heat source including dryers and curling irons should be used near it. A second treatment is recommended on day7-9 to kill newly hatched live.


Benzoyl alcohol or Ulesfia is not a pesticide. It is an aromatic alcohol that coats and suffocates lice. It is not ovicidal so a second application to kill newly hatched lice day 9 is recommended. It is considered less toxic and is approved for use in persons 6 months of age and older.


The most recent product FDA approved for lice treatment is Sklice with the active ingredient ivermectin. Sklice is toxic to both live lice and their eggs. Studies have shown it to be effective after a 10 minute application and nit combing is not required for effective treatment.Sklice can be used for children as young as 6 months.



Primary prevention is to avoid head to head contact during activities at home, school, camp, slumber parties etc.

Do not share brushes, combs, barrettes, towels, or ribbons

Do not share clothing such as coats, scarves, hats


We hope you find this information helpful.