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Crabs
(Pubic Lice)

Crabs Overview

"Crabs" is the common term for lice found in the pubic hair of humans. Crabs is a parasite infection medically known as Pediculosis pubis or pubic lice. Barely the size of a pinhead, lice are organisms that live only with the help of another organism, called a host. There are thousands of types of lice, some of which have developed an attraction to humans. The official name for the organism responsible for pubic lice is Pthirus pubis. Other lice that often infect humans are Pediculus humanus capitis (head lice) and Pediculus humanus corporis (body lice). The term "crabs" seems to come from the microscopic appearance of the pubic louse. The pubic lice organisms are visible to the naked eye in affected areas. The lice are typically seen attached to hair in pubic areas, but may sometimes appear in other areas of the body where coarse hair is present (such as beard, chest, armpits, etc.).

The pubic louse is distinct morphologically (somewhat rounded with three pairs of legs on either side of the body from which it takes its descriptive name) from the head and body louse. The female lifespan is slightly shorter (three weeks), and she produces fewer eggs per day (three) than her counterparts. The eggs attach to the base of the pubic hair shaft for approximately six to eight days before hatching.

Picture of pubic louse (crab)
Picture of pubic louse (crab)

Crabs Causes

  • The source of infection for pubic lice is intimate contact with an infected person. Therefore, pubic lice are often transmitted during sex.

  • Since transmission occurs during intimate contact, actual sexual intercourse is not necessary for the spread of pubic lice.

  • Pubic lice can also be transmitted by contact with contaminated belongings such as towels, bed sheets, or clothing.

  • Crabs are transmitted through any intimate contact. Lice do not jump or fly, so actual contact is necessary for transmission. An individual may acquire an infection by sharing bedding or towels.

  • Cats, dogs, and other pets are not involved in the spread of human lice. Your pet cannot become infested with human lice and transmit the lice to another person.


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Crabs (Pubic Lice)

Sexually Transmitted Diseases Overview

Sexually transmitted diseases (STDs) are among the most common infectious diseases in the United States today. More than 20 different STDs have been identified, and 13 million men and women are infected each year in the United States. Depending on the disease, the infection can be spread through any type of sexual activity involving the sex organs or the mouth; the infection can also be spread through contact with blood during sexual activity.

  • STDs affect men and women of all ages and backgrounds.

  • STDs have become more common, partly because young people are becoming sexually active at a younger age and are having multiple partners.

  • People can pass STDs to sexual partners even if they themselves do not have any symptoms.

  • Frequently, STDs cause no symptoms, especially in women.

    • Health problems from S...


Read the Sexually Transmitted Diseases article »



Read What Your Physician is Reading on eMedicine

Pediculosis »

Pediculosis (ie, louse infestation) dates back to prehistory. The oldest known fossils of louse eggs (ie, nits) are approximately 10,000 years old.

Read More on eMedicine »

Medical Dictionary