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Crab Lice / Pubic Lice / Pediculosis

Crab Lice / Pubic Lice / Pediculosis

Last Updated on Jan 30, 2020
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Pubic lice (Phthirus pubis) are tiny ectoparasites that infest areas with coarse hair on the human body, where they live on an exclusive diet of blood. They are most commonly found in the pubic region, arm pit, eye brows or eye lashes.


Pubic lice infestation is a global phenomenon and occurs in all races, ethnic groups, and in all sections of the society.(1 Trusted Source
Parasites - Lice

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There are three stages of pubic lice- the egg (nit), the nymph, and the adult forms.

Nits are the eggs of the lice and are laid by the female. They remain firmly stuck to the hair shaft and are not easily visible. The nymph, which hatches from the nit, is an immature form of the pubic louse. It takes about 2-3 weeks to mature into a sexually viable adult. The adult forms strongly resemble a crab when viewed through a magnifying glass, which is how they got the name, “crab lice”.

Adult lice are tan to grayish-white in color. The lice need blood to survive, therefore, if they fall off a person, they die within a day or two.(2 Trusted Source
Pubic Lice Symptoms & Treatment

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Risk Factors of Crab Lice

Pubic lice spread mostly through sexual activity and very rarely by coming into contact with bathing suits, sheets, blankets or toilet seats used by the infected individual. This is because the lice cannot exist away from the human body for too long.

Pubic lice are most commonly seen in adults; they are also occasionally seen in children who have had sexual exposure or who have been abused.

A person is at a great risk for contacting pubic lice if he/she has several sexual partners or has had an infected partner or is in the habit of sharing clothes or bedding with an infected individual.

Animals are incapable of spreading the lice to humans.


Symptoms and Diagnosis of Crab Lice

Pubic lice cause a great deal of itching which usually starts soon after being infected. However, in some individuals, itching begins only after 2-4 weeks of being infected.

Crawling lice or their eggs (nits) can be seen visibly. However, they may be difficult to detect as they are usually present in less numbers. Sometimes, a magnifying glass might be required to spot their presence.

Symptoms of pubic lice infection include sores in the pubic area as a result of bites from the lice and also the scratching. The skin near the affected area may also change to bluish gray in color as a result of the infection.

Symptoms of Pubic Lice

Young children may present with eye infection (blepharitis) which can be detected when the eye lashes are viewed through a magnifying glass, indicating the possibility of crab lice infection.

If self diagnosis is a problem, you may seek help from health experts. Those detected with pubic lice must also be checked for sexually transmitted infections (STIs) as the two usually go hand in hand.(3 Trusted Source
What are the Symptoms of Pubic Lice (Crabs)?

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Treatment for Crab Lice

Some of the best methods to treat pubic lice infection are-

  • Apply vinegar to the hair in the affected region and comb with a fine–toothed comb to remove nits.
  • Apply a prescription shampoo containing permethrin. Thoroughly work up a lather for five minutes before washing away the shampoo. Rinse thoroughly.
Treatment for Pubic Lice - Apply Shampoo in Hair
  • Most often, just a single treatment is needed. If required, a second treatment may be given after about a week.

Other measures that should be adopted include -

  • Wash and clean bedding and all clothing of the affected person in hot water.
  • Medicated sprays may be used to spray personal items that cannot be washed.
  • It is also possible to seal things in plastic bags for about two weeks to kill the lice.
  • If pubic lice are present on the eye lashes, ophthalmic-grade petrolatum ointment, a prescription medicine, may be applied on the rim of the eye for about ten days.
  • Ensure that your sexual partner(s) is/are informed of the infection.
  • Check yourself and your sexual partner(s) for STDs.(4 Trusted Source
    Pubic Lice (Crabs) - Including Symptoms, Treatment and Prevention

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Prognosis and Prevention of Crab Lice

The pubic lice infection will resolve itself once the person is treated. Avoid sexual contact in case of infection until the treatment becomes effective.

Avoid trying on dresses or bathing suits while mall shopping; in case you have to, make sure you wear underwear while trying them on.

Maintain personal hygiene at all costs.


  1. Parasites - Lice - (https://www.cdc.gov/parasites/lice/pubic/index.html)
  2. Pubic Lice Symptoms & Treatment - (https://www.avert.org/sex-stis/sexually-transmitted-infections/pubic-lice)
  3. What are the symptoms of pubic lice (crabs)? - (https://www.plannedparenthood.org/learn/stds-hiv-safer-sex/pubic-lice/what-are-symptoms-pubic-lice-crabs)
  4. Pubic Lice (Crabs) - Including Symptoms, Treatment and Prevention - (https://www.sahealth.sa.gov.au/wps/wcm/connect/public+content/sa+health+internet/health+topics/health+conditions+prevention+and+treatment/bites+burns+cuts+and+pests/pubic+lice/pubic+lice+crabs+-+including+symptoms+treatment+and+prevention)

Latest Publications and Research on Crab Lice

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