This insect is much smaller than head lice and body lice. It doesn’t cause us any actual damage, and isn’t considered an “infection” per se, since it lives on top of the skin (as opposed to germs that enter our bodies). Still, pubic lice infestations can result in most annoying itching (and sometimes the scratching we do might provoke skin infections). Also, they carry a stigma since they’re transmitted sexually, and can thus ruin relationships.
The lice themselves can be hard to see, since they’re so small and fleeting. We usually make the diagnosis by noting nits, lice eggs, which are whitish or dull yellow specks that adhere firmly to hair shafts. If the thing we see can be flicked off, it’s not a nit. Also, live nits are found within 6 mm (1/4 inch) from the skin. Anything further up the hair shaft has hatched already.
Another finding for diagnosing lice are “maculae cerulea,” blue-gray spots on the skin caused by enzymes in lice salvia, released while they suck (Figure 1 below). Nothing else can cause them.
What many people don’t realize is that pubic lice can scurry from hair to hair, as far as possible. On hairy individuals (mostly men), they can extend up the back and down the legs. If creams or lotions are used for treatment (as opposed to oral medications), they need to be applied widely, or they’ll fail. Also, since most such topically-applied products don’t kill eggs, retreatment must be performed at 9 days, to cover the louse which might have hatched just after the first treatment, but before it’s old enough to start laying its own eggs at 10 days of life.
I couldn’t find a good picture of nits in the genital area, but Figure 2 shows them on eyelashes. They look the same, but treatment is hard because the usual pediculicides (louse-killers) are dangerous if they get in the eye. How did the lice wind up there? Surely because the patient’s face got too close to whatever part of someone else’s body.