Boy odour (spelled body odor in the U.S.), often abbreviated as B.O., or bromhidrosis (also called bromidrosis, osmidrosis and ozochrotia) is the smell of bacteria growing on the body. These bacteria multiply rapidly in the presence of sweat, but sweat itself is almost completely odorless. Body odor is associated with the hair, feet, groin (upper medial thigh), anus, skin in general, armpits, genitals, pubic hair, and mouth.