The pubic louse, or Pthirus pubis, is a parasitic insect that feeds on the blood of humans. Pubic lice are also known as crab lice, or simply "crabs". They have acquired this nickname due to their large front legs that look much like the pincers of a crab. Pubic lice are transmitted via intimate physical contact, such as sexual intercourse, and are less often transmitted by infested materials such as bed linens or clothing. While lice cannot live without a human host for more than two days, they are very nimble insects and can easily climb on and attach to hair without detection.
Pubic lice feed on blood by biting skin at the base of a hair follicle. They prevent clotting of the blood, a normal bodily repair mechanism, by an anticoagulant in their saliva. This along with other substances in the louse's saliva is seen as foreign by the human immune system, resulting in a mild allergic reaction (inflammation and itching) around the bite. While the itchy feeling caused by the allergic reaction is more annoying than harmful, excessive itching can quickly damage the skin of the infested area.
The Body's Largest Organ: The Skin
You may have heard the factoid that the skin in the body's largest organ. But what exactly is its function? The immune system is usually what comes to mind when we think about defense against disease. But the skin is actually the first line of defense against pathogens. While the skin is virtually impermeable, resistant to mild mechanical trauma, and protects internal organs by blocking harmful radiation, the skin also releases slightly acidic secretions, making it an inhospitable environment to most harmful bacteria as well as viruses. Scratching can quickly sacrifice the skin's integrity, allowing for easier infiltration of harmful pathogens.
While the secondary infections caused by a lice infestation can have frightening and painful results, such infections can be easily avoided. There are many shampoos and ointments available both with a prescription or over-the-counter that work well. Although lice cannot live off of a human host for more than two days, all suspect bedding, undergarments, and other linens such as towels must be washed in hot water and thoroughly dried under hot air. Pubic lice are most easily spread during intimate contact, such as sexual intercourse. Limiting the number of one's sex partners is therefore essential to preventing a lice infestation.