What Are Pubic Lice (Crabs) & How Do You Get Them?

Pediculosis Pubis is an infestation by the crab louse, Pthirus Pubis. Also known as “crabs”, pubic lice infestation is a relatively common but unreported sexually transmitted disease (STD) and it is estimated that 2% of the world population has had this infestation prior.

Pthirus Pubis

The crab louse is a small, translucent parasite around 1mm in length. It is one of the 3 species of lice that infects humankind and is differentiated by its almost round body. Crab Lice is exclusively found on human hosts and requires human blood to survive. As its name suggests, it is usually found in the hair at the pubic region but it can also be found in other coarse hair of the body, like eyebrows, armpits, beards for example.


The main symptom of a pubic lice infestation is intense scratching, typically at the pubis and the perineum. There can be also pale bluish discoloration of the skin following prolonged infestation as a result of injection of lice salivation during feeding.

When the eyelashes are involved, there can be crusting/matting of the eyelashes with eye irritation as well. Children might be seen continuously rubbing their eyes.

Thankfully, pubic lice are not known to be any vectors of any harmful diseases, unlike the body lice.


Diagnosis is usually made by direct visualization of the lice or nits (lice eggs) by the patient or the doctor. No other blood tests or swabs are required.


Transmission is usually during sexual contact with skin to skin contact.

Transmission via the environment, for example through clothing, towels or linen may also occur but are less common.

One is unlikely to catch pubic lice from a toilet seat as the organism gravitates towards a warm environment and is not adapted to crawl on smooth surfaces.


Topical medication is available for treatment of pubic lice and a few applications might be required for complete eradication.

Shaving of the affected area is not required but the manual removal of nits with a nit comb or tweezers is recommended.

It is also important for close sexual contacts of the affected patient to be screened for pubic lice infestation as well. Abstinence is also recommended until re-examination to rule out persistent infection.

Bedding and clothing of the affected patient should also be machine washed in hot water and dried. There is no need for fumigation of the entire room.


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