Pubic lice, also known as crab lice, are tiny parasitic insects that infest the coarse hair in the genital area. They are about the size of a pinhead and can cause itching and discomfort. These lice feed on human blood and are typically spread through close physical contact, including sexual activity. While pubic lice are most commonly found in the genital region, they can also inhabit other coarse body hair, such as in the armpits or chest. Treatment usually involves over-the-counter or prescription lotions and shampoos designed to kill the lice and their eggs.