What exactly causes bv?

PH change: Bacterial vaginosis is due to a shift in the natural flora of the vagina. It is not a sexually transmitted disease. It can be prevented by eating yogurt, avoiding douching, wiping front to back.

Altered environment: A healthy vagina normally has many species of bacteria, mostly lactobacilli. Lactobacilli are useful bacteria, as they make Lactic Acid & peroxide which keep the vagina at a slightly acidic ph (protects against infection). A change in normal bacteria, including reduction of lactobacilli, may be due antibiotics or ph imbalance, allows a mix of more resistant bacteria to grow--causing bv.