Causes of Bacterial Vaginosis

Bacterial vaginosis occurs due to an overgrowth of unhealthy anaerobic bacteria and the loss of the healthy bacteria Lactobacillus in the vaginal tract 2. This infection with unhealthy bacteria can only come about when the vagina changes pH from its normally acidic state to alkaline conditions. A rise in the pH of vaginal secretions to over 4.5 typically is seen when bacterial vaginosis is present. Several things can cause this change and lead to a bout of bacterial vaginosis.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.

Sexual Intercourse

Sperm is alkaline, having a high pH value, and when it comes in contact with the normally acidic vagina, it can raise the pH of the vaginal tract, leaving a door open for the overgrowth of anaerobic bacteria. When bacterial vaginosis occurs via sexual transmission, there can be a noticeable alkaline scent after sex. This change in vaginal conditions frequently occurs when intercourse occurs with a new partner, so limiting sexual partners can help prevent bacterial vaginosis caused by sex. Condom use may also help, since it limits the contact between alkaline sperm and the acidic vagina. Treating the male partner for bacterial vaginosis does not have any effect on its recurrence, since the bacterial overgrowth is not a sexually transmitted disease but one caused by an alteration in the normal pH levels of the vagina.


Douching alters the natural pH of the vagina, leaving it vulnerable to infection. In a 2002 study in the journal Obstetrics & Gynecology, researchers found that frequent douching of once per month or more raised the risk of developing bacterial vaginosis and also was associated with the growth of two particular microorganisms implicated in the disease, Gardnerella vaginalis and Mycoplasma hominis 2. Women in the study who douched regularly were also found to have less of the healthy lactobacilli in their vaginal tracts.


Hormonal changes during menopause can change the naturally acidic vagina to a more alkaline condition. Estrogen is the hormone responsible for maintaining acidity of the vaginal tract, and during menopause, production of estrogen drops off rapidly. Estrogen creams, pills or an estrogen ring inserted into the vagina can help counteract these changes and maintain the normal protective acidity.

Heavy Menstrual Periods

Women with heavy menstrual periods may find that they develop bacterial vaginosis frequently after experiencing heavy blood flow. This occurs because blood is naturally alkaline, and an abundance of blood in the vaginal tract can alter conditions there enough to promote the development of bacterial vaginosis. Women who recurrently experience this problem may need to get a doctor's prescription for medication to reduce blood flow during the menstrual cycle.