How do u get bacterial vaginosis?

Vaginal pH change: The vagina is kept at a pH(acidity/alkalinity) scale of 4.5 to 5.5.(mildly acidic) by Doderleins bacteria that are "native"(beneficial) to the vagina and maintain a rather constant pH. Several events can abnormally change the pH or kill the "good" bacteria, such as frequent douching, perfumed soap use, non-hygienic sexual partners, and unsanitary dildos. BV thrives on those situations.

Imbalance of flora: Bacterial vaginosis is a very common vaginal infection in women. It is from bacteria that live normally in the vagina and for unclear reasons, overgrow and cause symptoms. Sexual contact with new and multiple male and female partners was associated with an increased risk of BV.

BV is an imbalance: Sexual activity with new or multiple partners is a risk factor although it is not an STI per se and there is no evidence that treating a partner will help. BV mostly involves a change in the numbers and balance of normal bacteria that live in the vagina with certain types of normal bacteria increasing in concentration and other types decreasing. Douching and cigarette smoking are risk factors.