Bacterial vaginosis keeps coming back because the bacteria that cause it form a protective layer on the vaginal wall that standard antibiotics can’t fully eliminate. About 58% of women who take oral antibiotics for BV will have a recurrence within 12 months, and nearly a quarter relapse within the first month alone. If you’re dealing with this cycle, you’re far from alone, and the reasons behind it are increasingly well understood.
The Biofilm Problem
The main culprit behind recurrent BV is a bacterium called Gardnerella vaginalis, which has a unique ability that sets it apart from other vaginal bacteria: it can build biofilms. A biofilm is essentially a dense, sticky colony of bacteria that anchors itself to the vaginal lining and shields the organisms inside from antibiotics, acid, and your body’s own defenses. Research published in The Journal of Infectious Diseases found that biofilms were present on 90% of vaginal tissue samples taken from women with BV, with Gardnerella as the dominant species in those communities.
What makes this especially frustrating is that once the biofilm is established, it becomes a scaffold for other harmful bacteria to join. Gardnerella adheres to vaginal cells first, then secondary bacteria incorporate themselves into the structure. Together, they form a self-reinforcing community. When you take antibiotics, the medication kills the free-floating bacteria and your symptoms resolve, but the biofilm persists on the vaginal wall. Once you stop treatment, the surviving bacteria inside the biofilm repopulate, and symptoms return.
Gardnerella biofilms also show higher tolerance to hydrogen peroxide and lactic acid, the two main weapons that healthy vaginal bacteria use to keep harmful organisms in check. This means even if your good bacteria start recovering after treatment, they may not be strong enough to dismantle the biofilm on their own.
Your Vaginal Microbiome Matters
A healthy vagina is dominated by Lactobacillus bacteria, which produce lactic acid and keep the pH low (acidic), creating an environment hostile to BV-causing organisms. But not all Lactobacillus species offer the same protection. A vaginal environment dominated by Lactobacillus crispatus has the lowest pH, the lowest levels of inflammatory markers, and the lowest risk of gynecologic complications. It’s considered the gold standard for vaginal health.
Another common species, Lactobacillus iners, is less protective. Women whose vaginal flora is dominated by L. iners are more susceptible to shifts toward BV. Interestingly, studies have shown that probiotic strains of L. crispatus have difficulty colonizing women who already have L. iners as their dominant species, which may partly explain why some women seem more prone to BV than others regardless of what they do.
Several things can disrupt this microbial balance. Antibiotic use (even for unrelated infections), douching, and hormonal changes can all reduce Lactobacillus populations and open the door for BV-associated bacteria to take over.
How Sex Plays a Role
Sexual activity is one of the most consistent risk factors for both initial BV and recurrence. Semen is alkaline, with a pH around 7.2 to 8.0, while a healthy vagina sits around 3.8 to 4.5. Exposure to semen temporarily raises vaginal pH, creating conditions that favor BV-associated bacteria over protective Lactobacillus. Lubricants can have a similar effect depending on their formulation.
There’s also growing evidence that BV-causing bacteria can live on male partners. Research has found that biofilm-forming Gardnerella is present in the sex partners of women with BV, and that high-density clusters of these bacteria on a male partner can reintroduce the infection after treatment. This helps explain a pattern many women recognize: BV clears up with antibiotics, then comes back after resuming unprotected sex with the same partner.
Treating Your Partner Can Cut Recurrence in Half
A landmark clinical trial published in the New England Journal of Medicine in 2025 tested whether treating male sexual partners could break the cycle. The study enrolled over 150 women in monogamous heterosexual relationships, all with BV. Half the male partners received a combination of oral and topical antibiotics, while the other half received no treatment.
The results were striking enough that the trial was stopped early. BV recurred in 63% of women whose partners went untreated, compared to just 35% of women whose partners received antibiotics. That’s nearly half the recurrence rate. Among couples where the male partner fully adhered to the treatment regimen, the recurrence rate dropped even further. This is a recent finding, and clinical guidelines are still catching up, but it’s worth discussing with your healthcare provider if you’re in a sexual partnership and struggling with repeat infections.
Reducing Your Risk of Recurrence
Using condoms consistently is one of the simplest ways to lower BV recurrence. Condoms prevent semen from altering vaginal pH and reduce the transfer of BV-associated bacteria between partners. If condoms aren’t practical for you, consider asking about concurrent partner treatment.
Lubricant choice matters more than most people realize. If you’re prone to BV, look for water-based or silicone-based lubricants with a pH close to 4.5 and an osmolality (a measure of dissolved particles) below 1,200 mOsm/kg. The closer to 380, the better. Many popular lubricants are far too alkaline or concentrated for vaginal health.
Oral probiotics containing specific Lactobacillus strains have shown some promise. In a randomized, placebo-controlled trial of 64 women, daily oral capsules containing L. rhamnosus GR-1 and L. fermentum RC-14 taken for 60 days restored normal vaginal flora in 37% of women with asymptomatic BV, compared to 13% on placebo. Perhaps more notable: none of the women taking the probiotic developed new BV during the study period, while 24% of the placebo group did. These are specific strains, though, and not all probiotic products contain them. Check labels carefully.
Avoid douching, vaginal deodorants, and scented soaps inside the vagina. These disrupt the acidic environment that keeps protective bacteria dominant. The vagina is self-cleaning, and adding products to it generally does more harm than good.
Why Antibiotics Alone Aren’t Enough
Standard BV treatment with oral antibiotics works well for immediate symptoms but fails to address the underlying biofilm. This is why recurrence rates are so high. Your doctor may prescribe a longer or suppressive course of antibiotics for recurrent BV, which can help extend the time between episodes, but biofilm persistence means the infection often returns once suppressive therapy stops.
The combination of antibiotics, partner treatment, barrier methods during sex, and targeted probiotics represents the most comprehensive approach currently available. No single intervention solves the problem on its own, but layering these strategies together gives you the best chance of breaking the cycle.