14 October 2019, by GARRIDO P.


Chapter written with the help of the EADV, the Fondation René Touraine and the Therapeutics in Dermatology


Pediculosis is a very common infestation of hairy body sites by lice. There are three types of lice: head lice infest the hair and scalp, crab lice the pubic area and body lice the clothing, moving to the skin in order to feed.


The majority of the cases of pediculosis are not associated with any symptom. When symptoms are noted, people can have itching or feel something moving over their head and/or body. It may take up to three weeks after the transmission for a person to start feeling itch. Red spots can be seen at the site of bites.

In rare cases, scratching can cause a secondary bacterial infection, and patients can present pain and fever.


Pediculosis capitis is the infestation of the hair and scalp by lice and affects mainly children between 3 and 11 years old, but adults can also be affected, particularly in resource-poor communities. Females are affected more frequently because long hairs have a higher probability of contacting with the lice. Head lice infestation is frequent in children in the same school.

Pediculosis corporis affects both children and adults and is common in the setting of poverty, war, and homelessness.

Crab lice infestation is a sexually transmitted infection and only rare cases are observed in non-sexually active people, mainly due to direct contact with clothes infested.

Lice don’t jump or fly. Transmission only occurs by direct contact or by sharing infested objects, such as clothes.

Lice only infest humans. Domestic animals, such as dogs and cats, are not affected and are not contagious.


Pediculosis capitis is caused by the human louse Pediculus humanus capitis and pediculosis corporis by Pediculus humanus humanus.

Head lice are spread by direct contact with the hair of someone who is infected.

Body lice are mainly transmitted by direct contact with surfaces with the infestation, such as clothes, towels or pillows.

Pubic pediculosis is caused by the louse Pthirus pubis and is transmitted by sexual contact with someone who is infected. In rare cases the transmission results of direct contact with infested clothes.


The diagnosis is made by the identification of the lice in a hair, which can be done by direct observation with the naked eye. The diagnosis of pediculosis capitis is best performed by evaluating the entire scalp with the help of a comb.


The most effective treatment available is permethrin 1% cream applied to the affected areas and washed off after 10 minutes. Two applications are necessary for effective treatment, separated between 7 to 10 days.

Lice and nit can be removed from the hair by combing, complementing treatment.

In pubic and pediculosis corporis, clothes, towels and other daily materials should be washed at high temperatures or sealed and stored in a plastic bag for at least 3 days.

The household members and close contacts should be evaluated and those with active infestation should be treated simultaneously.

In pubic pediculosis, the infested patient and their sexual partners should remain sexually abstinent until infestation is solved. All sexual partners of the previous 3 months should be evaluated and treated, if necessary. Persons with pubic lice should be evaluated for other sexually transmitted diseases.

One week after finishing treatment, there should be no evidence of live lice for the infestation to be considered cleared.


  • Cutting or shaving hair is not necessary.
  • After treatment, checking the hair and combing to remove nits and lice every 2 days may be helpful
  • Alternative treatments, such as oil, vaseline and “hair ointments” are not effective
  • There is no need for prophylactic treatments in the contacts without evidence of pediculosis.
  • It may take up to 8 to 12 hours for the lice to die after treatment. It is not necessary to retreat if lice are still moving within this period.
  • Ask for an urgent appointment if you feel sick, with fever and intense pain over your head

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