Vaginal Flora

The vaginal flora is the bacteria that live inside the vagina. The normal vaginal flora is dominated by various lactobacillus species.

Lactobacilli help to keep the vagina healthy by producing lactic acid, hydrogen peroxide, and other substances that inhibit the growth of yeast and other unwanted organisms. They maintain the vagina at a healthy pH of around 4.

This mildly acidic environment helps protect against infection. So do the other substances they produce. These bacteria are an important part of a healthy vaginal ecosystem.

Female doctor going over test results with patient
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Why Vaginal Flora Is Important

A hallmark of bacterial vaginosis (BV) is the disruption of this normal vaginal flora and a loss of lactobacilli. This can not only be unpleasant in and of itself. It can also leave a woman more susceptible to HIV and other sexually transmitted infections.

Bacterial vaginosis is actually caused by an overgrowth of bacteria that normally exist at low levels in the vagina. When the lactobacillus population is disrupted, these bacteria take over. 

The bacteria associated with BV make a number of volatile amines. These chemicals are what cause the distinctive odor associated with BV. This odor tends to be stronger after sex, particularly unprotected sex, because the amines become smellier at the higher pH associated with semen.

However, despite the association, BV is not caused by sperm. In fact, the greatest evidence for sexual transmission of bacterial vaginosis is in lesbians.

It's not clear whether BV can be transmitted during vaginal intercourse. BV is most often diagnosed by a test called a wet mount.

Restoring Healthy Vaginal Flora

One of the difficulties in treating BV and related conditions, such as yeast infections, is figuring out how to restore the normal vaginal flora. Sometimes the bacterial populations return to normal proportions after treatment. Other times they don't.

In order to help restore a lactobacillus-dominated flora, a number of researchers are looking at probiotic pills and suppositories. These treatments would contain lactobacillus species.

The hope is that those bacteria would grow and recolonize the vagina. To date, results have been somewhat positive, if preliminary. Still, if they're borne out, probiotics may be a new way to improve vaginal health and restore healthy vaginal flora.

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3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Miller EA, Beasley DE, Dunn RR, Archie EA. Lactobacilli dominance and vaginal pH: why is the human vaginal microbiome unique?. Front Microbiol. 2016;7:1936. doi:10.3389/fmicb.2016.01936

  2. Lobo, RA, Gershenson, DM, Lentz, GM, Valea, FA. Comprehensive Gynecology. New York, NY: Elsevier Health Sciences; 2016.

  3. Heczko PB, Tomusiak A, Adamski P, et al. Supplementation of standard antibiotic therapy with oral probiotics for bacterial vaginosis and aerobic vaginitis: a randomised, double-blind, placebo-controlled trial. BMC Womens Health. 2015;15:115. doi:10.1186/s12905-015-0246-6

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