It's possible to be infested with pubic lice and have no symptoms, but itching is usually present. This can worsen at night when the louse becomes active and buries its head inside a pubic hair follicle to feed on human blood. It excretes a substance that causes the itching. Sometimes the bite can cause the area to become inflamed and turn bluish gray. Although lice themselves do not cause a rash, the constant itching and scratching can cause the area to become raw, resulting in a secondary bacterial infection.
Scratching also can aid the spread of lice.
For specific medical advice, diagnoses, and treatment, consult your doctor.