When people think genital itch, they usually think yeast. But yeast typically produces an internal vaginal itch, not outside on the vulva. If you are itching where your skin touches your underwear pubic lice has to be considered in the differential diagnosis.
Pubic lice are insects called Pthirus pubis, that, er, hang out around the pubic hair. They are also commonly called crabs, because of their crab-like appearance under the microscope. Pubic lice feed on blood and it’s the reaction to the bite that produces the itch. While pubic lice primarily infect pubic hair, they can actually infect coarse hair anywhere on the body (eyelashes, armpits, beard, chest hair etc). Pubic lice don’t infect the hair on the head because the distance between the coarse hair follicles is an ideal habitat; apparently the follicles on the head are not.
Pubic lice have to crawl to get where they are going so they are spread by sexually contact (close genital touching will suffice, or even oral sex for transmission to eyelashes, so intercourse per se is not actually required. I know, I know. People keep telling me that I am ruining oral sex one post at a time, but it’s information people! You can’t make informed choices without information!). You can also catch pubic lice by sharing clothing or bedding. You can’t get lice from a toilet seat – they can’t grip to the smooth surface.
How do you know if you have crabs? The number one symptom is itch, but if you have a close look (a magnifying glass may be required) the lice will be visible crawling around and their eggs (nits) will look like tiny grains of rice stuck to the hair. If you are not sure you should see a health-care professional to get the right diagnosis.
Treatment for pubic lice is available over-the-counter, a cream containing the drug permethrin, but there are other medications. After treatment you will need to pull the nits off the hair shaft with your fingernails or a fine-toothed comb. If you suspect you have lice on your eyelashes or eyebrows you must see a doctor, because treating this area requires a prescription ointment. If you are pregnant or breast-feeding you should talk with your doctor before starting therapy.
To kill any lice on clothes or in your bedding you should machine wash in hot water and machine dry on hot anything that has been worn or slept in for the past 2-3 days. Dry-cleaning is also an option. Place any clothes or bedding that cannot be washed in a sealed plastic bag for 2 weeks. This will kill the lice because they cannot live for more than a day or two without blood.
Remember sexually transmitted infections travel in packs, so if you caught pubic lice you may have also been exposed to another infection, so it’s a good idea to get tested for other STDs as well.