Researchers have had difficulty determining exactly what causes bacterial vaginosis. At present, it seems to be that a combination of multiple bacteria must be present together for the problem to develop. Bacterial vaginosis typically features a reduction in the number of the normal hydrogen peroxide-producing lactobacilli in the vagina. Simultaneously, there is an increase in concentration of other types of bacteria, especially anaerobic bacteria (bacteria that grow in the absence of oxygen). As a result, the diagnosis and treatment are not as simple as identifying and eradicating a single type of bacteria. Why the bacteria combine to cause the infection is unknown.
Certain factors have been identified that increase the chances of developing bacterial vaginosis. These include multiple or new sexual partners, vaginal douching, and cigarette smoking. However, the role of sexual activity in the development of the condition is not fully understood, and bacterial vaginosis can still develop in women who have not had sexual intercourse.
