Bacterial vaginosis is a condition caused by a change in the makeup of the bacteria that are normally present in the vagina. It can be associated with any of a number of bacteria.
The vagina normally contains bacteria, which have the beneficial side-effect of staving off yeast infection. However, when conditions are changed through frequent cleaning of the vagina or frequent sexual intercourse, this natural balance can change and different types of bacteria not normally present can proliferate. These bacteria cause an unpleasant smell, a change in acidity and mild inflammation.