Bacterial vaginosis, commonly called BV, is a vaginal condition caused by an imbalance in the bacteria that naturally live in the vagina. It’s the most common vaginal infection in women of reproductive age. Normally, beneficial bacteria called lactobacilli keep the vaginal environment slightly acidic (below a pH of 4.5), which prevents harmful organisms from gaining a foothold. In BV, those protective bacteria decline and are replaced by an overgrowth of other bacterial species, shifting the pH higher and triggering symptoms like unusual discharge and odor.
BV is not a sexually transmitted infection, though sexual activity is one of several factors that can set the stage for it. Many people with BV have no symptoms at all, and roughly 30% of cases resolve on their own without treatment.
What BV Feels Like
The hallmark symptom is a thin, grayish-white discharge that coats the vaginal walls evenly. Unlike the clumpy discharge associated with yeast infections, BV discharge has a smooth, almost milklike consistency. It often comes with a distinct fishy smell that can become stronger after sex, because semen temporarily raises vaginal pH and amplifies the odor.
Some people also notice mild itching or irritation, but BV rarely causes the intense burning or swelling that other vaginal infections do. In fact, many people with BV have no noticeable symptoms. One study found the bacteria most associated with BV living in the vaginal tracts of up to 50% of women without any complaints, suggesting a spectrum between normal variation and active infection.
Common Risk Factors
Anything that disrupts the natural balance of vaginal bacteria can increase your risk. The most well-studied triggers include:
- Douching. One cross-sectional study found that douching within the past two months nearly tripled the odds of having BV. Douching with soap, water, or commercial antiseptic products can wash away protective lactobacilli and create space for other bacteria to take over.
- New or multiple sexual partners. Research consistently links new partners and less frequent condom use with BV onset. Sexual intercourse introduces semen, which raises vaginal pH and temporarily shifts the bacterial environment.
- Spermicide use. Day-to-day variability in vaginal flora has been tied to spermicide use alongside the factors above.
Hormonal changes during menstruation can also play a role, since menstrual blood is more alkaline than the usual vaginal environment. Some research has noted that Black women tend to have a naturally higher vaginal pH on average, which may partly explain disparities in BV rates across racial groups.
How BV Is Diagnosed
A clinician can diagnose BV during a routine pelvic exam using a set of four bedside checks known as the Amsel criteria. A diagnosis requires at least three of the following:
- Thin, homogeneous gray-white discharge
- Vaginal pH above 4.5
- A fishy odor when a drop of potassium hydroxide is added to a sample of the discharge (the “whiff test”)
- Clue cells visible under a microscope, which are vaginal skin cells covered with a layer of adherent bacteria
Labs can also grade a vaginal swab under the microscope using a scoring system that quantifies how many protective bacteria versus BV-associated bacteria are present. This approach is considered the gold standard for research, but in everyday clinical practice the Amsel criteria are faster and widely used.
Treatment Options
BV is treated with antibiotics, typically taken either by mouth or applied inside the vagina as a gel or cream. Most courses last five to seven days. The oral and topical routes are considered equally effective, so the choice often comes down to personal preference and whether you’d rather take a pill or use a vaginal product.
While antibiotics clear the immediate infection effectively, recurrence is the real challenge. Between 50% and 80% of women experience BV again within 6 to 12 months after finishing a course of antibiotics. That high recurrence rate has led researchers to look at additional strategies.
Partner Treatment
For years, treating male sexual partners was not recommended. That changed in 2025, when the American College of Obstetricians and Gynecologists issued its first recommendation to consider concurrent treatment of male partners for people with recurrent BV. The updated guidance also suggests shared decision-making about partner treatment for same-sex partners and even for first episodes of BV. The rationale is that BV-associated bacteria can be carried by partners and reintroduced after treatment.
Boric Acid Suppositories
Boric acid vaginal suppositories have gained attention as an add-on option for recurrent BV. In a study of 52 women with three or more episodes in a year, a 14-day course of 600 mg boric acid suppositories lowered diagnostic scores from clearly abnormal to normal range in about 88% of participants. Vaginal odor dropped from 92% of participants at baseline to under 2% after treatment. Side effects were mild and uncommon, occurring in fewer than 8% of women. These suppositories are available over the counter, but they’re best used under guidance from a healthcare provider, especially since they are toxic if swallowed.
Why BV Matters During Pregnancy
BV carries particular risks for pregnant women. A large meta-analysis covering more than 290,000 pregnancies found that women with BV faced roughly double the odds of preterm delivery compared to women without it. Preterm birth is the leading cause of newborn complications, so this is not a minor statistical bump. The study’s authors argued that routine screening and treatment of BV should be part of standard prenatal care to help reduce preterm births and the infant mortality that follows.
Outside of pregnancy, untreated BV can also increase susceptibility to other infections. The disrupted bacterial balance and elevated pH make the vaginal environment more hospitable to sexually transmitted organisms, and BV has been linked to a higher risk of pelvic inflammatory disease.
Reducing Your Risk of Recurrence
Because BV comes back so frequently, prevention matters as much as treatment. The most evidence-backed steps are straightforward: avoid douching entirely, use condoms consistently, and minimize the use of scented products in or around the vagina. These actions help preserve the acidic environment that lactobacilli need to thrive.
If you’re dealing with recurrent episodes, it’s worth discussing partner treatment with your provider, given the recent shift in clinical recommendations. Some clinicians also prescribe longer or maintenance courses of antibiotics, or suggest boric acid suppositories as a follow-up to standard treatment, to extend the time between recurrences. BV can be frustrating to manage, but understanding what drives it gives you more tools to break the cycle.