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You may have a diagnosis of bacterial vaginosis (BV) with or without symptoms. Either way the problem is the same: disruptive bacteria have colonised the vagina. Often, these bacteria build a sticky bacterial biofilm1–2 over your vaginal cells to shield their colony from whatever you throw at it.
The usual treatment for BV is antibiotics, and they do work for plenty of people. But the three-month success rate sits at around 50 per cent, and somewhere between half and 80 per cent of women are back with BV within a year.3–4 If that is you, it is almost never because you’ve done something wrong. The antibiotic has simply dealt with part of the problem and left the rest.
Why don’t antibiotics always clear BV?
There are a few reasons antibiotics don’t work on BV for everyone, and they often stack up together. Antibiotics knock down the free-floating disruptive bacteria, which is why your symptoms often ease for a while.
What they struggle with is the biofilm – the protective layer the bacteria hide under – and everything that biofilm allows: antibiotic resistance, several species protecting each other, reinfection, and a vagina that hasn’t yet rebuilt its protective bacteria.
So a course of metronidazole can clear the surface and still leave the foundations in place. A few weeks later the colony rebuilds, which is why BV keeps coming back after antibiotics for so many women. In most cases it never fully left.
What is a BV biofilm?
A biofilm is a slimy, self-made matrix that bacteria glue to a surface – in this case, the epithelial cells lining your vagina. It is mostly built by Gardnerella species, with other disruptive bacteria such as Prevotella and Fannyhessea (Atopobium) vaginae moving in alongside them.1–2
Once that matrix is established, it does a few annoying things at once. It lowers the acidity of the vagina, crowds out and kills off your protective Lactobacillus, and drives the discharge and odour that send most people to the doctor in the first place.
And this is where treatment comes unstuck. Antibiotics can only punch a few holes in that matrix, not dissolve it. The bacteria sheltering deep in the biofilm survive, and they get straight back to work once the drug clears.
Antibiotics most commonly used to treat BV
These are the standard first-line options. They are a reasonable place to start, and for some people they are all that’s needed.
- Metronidazole (Flagyl, oral; MetroGel, vaginal) – the most commonly prescribed
- Clindamycin (Cleocin, oral or vaginal; Clindesse, vaginal)
- Tinidazole (Tindamax, oral)
- Secnidazole (a single oral dose, newer)
If you want the detail on how these drugs work and where they fall short, we cover it in understanding antibiotics.
The main reasons antibiotics fail on BV
The biofilm shields the bacteria
This is the big one. The biofilm physically blocks the antibiotic from reaching the bacteria deep inside, so the dose that would easily kill free-floating Gardnerella simply can’t get to the ones that count.4–5 Standard antibiotic therapy was never designed to dismantle a biofilm, which is a large part of why recurrence rates sit so stubbornly above 50 per cent.
Antibiotic resistance
Biofilm-forming Gardnerella are far less sensitive to metronidazole than free-floating bacteria, and resistance can actually develop after treatment – isolates that were sensitive at the start can come back resistant a few months down the track.4 Repeated short courses can quietly select for the hardier bacteria, which is one reason the antibiotic merry-go-round tends to get less effective the more you ride it.
Several species protecting each other
BV is rarely a one-bacteria show. When Gardnerella, Prevotella and Fannyhessea vaginae share a biofilm, they cooperate in ways that make the whole community more tolerant of antibiotics than any of them would be alone.2,6 Treat one and the others keep the structure standing.
Reinfection from a partner
This one has shifted recently. A 2025 randomised trial (StepUp) treated the male partners of women with BV using oral and topical antibiotics at the same time as the women were treated. Recurrence dropped to 35 per cent, compared with 63 per cent when only the woman was treated.7
In other words, the male genital tract can act as a reservoir that re-seeds BV, and ignoring it sets some couples up to fail. Condoms can also reduce reinfection while you get on top of it.
The wrong problem was treated
Not every stubborn discharge is classic BV. Aerobic vaginitis, a yeast infection, cytolytic vaginosis, or a mix of these can look similar but need very different handling.8 Many of the relevant bacteria don’t even show up on a routine culture, so if BV keeps returning, it is worth checking that you are actually treating what’s there.
The protective bacteria were never rebuilt
An antibiotic clears space, but it doesn’t refill it. If the protective Lactobacillus – especially Lactobacillus crispatus – don’t recolonise and re-acidify the vagina, that empty, less-acidic terrain is exactly what the disruptive bacteria love to recolonise.9 Clearing BV is only half the job; holding the ground afterwards is the other half.
How recurrent BV affects your vagina
Beyond the discharge, odour and irritation, a vagina stuck in BV is running with the wrong chemistry. The pH climbs out of its healthy acidic range, the protective Lactobacillus stay suppressed, and the tissue is left more exposed than it should be.
That matters because long-running BV is linked to a higher risk of catching and passing on sexually transmitted infections, including a raised risk of HIV, as well as complications in pregnancy and after gynaecological procedures. None of this is meant to frighten you – it is simply why we think recurrent BV deserves proper attention rather than another quick script and a shrug.
What actually helps when antibiotics aren’t working
In our clinic, recurrent BV that hasn’t budged after rounds of antibiotics is one of the most common things we see, and a persistent biofilm is usually at the heart of it. The approaches with the best evidence all work on the parts antibiotics miss: the matrix, the missing protective bacteria, and the steady trickle of reinfection.
Disrupting the biofilm
The logic here is simple: if you can collapse the matrix, the bacteria underneath lose their shelter and become far easier to clear. One way researchers are doing this is with agents that pull the minerals out of the biofilm scaffolding so it falls apart.
A phase 2 trial of a boric acid plus EDTA vaginal product (TOL-463) – EDTA being a mineral-binding ‘chelator’ – reached clinical cure rates of around 50 to 59 per cent for BV, while sparing the protective lactobacilli.10 We dig into the detail in can boric acid really disrupt BV biofilms?
This is the same principle we use in clinic: ingredients that draw minerals out of the biofilm matrix, collapsing its structure and leaving the bacteria underneath exposed to herbal medicine that can actually reach them.
Herbal antimicrobials
Several plant compounds have measurable activity against Gardnerella and its biofilm in the laboratory. Thymol, from thyme, inhibits both newly formed and mature Gardnerella biofilms in vitro.11
Berberine, tea tree oil and garlic-derived allicin have all shown antibacterial and anti-biofilm activity against BV bacteria, and a 2025 review of natural molecules and nutraceuticals for BV maps out where the human evidence is genuinely promising and where it is still early.12 Aloe vera is another with biofilm research behind it.
Used properly, and alongside biofilm disruption, targeted botanical antimicrobials are a real and increasingly well-studied tool. The research base is growing quickly, and it deserves to be taken seriously rather than waved off as folk medicine.
Rebuilding your protective bacteria
Putting Lactobacillus crispatus back is one of the most promising directions in BV research. In a randomised trial, a live L. crispatus vaginal product (LACTIN-V) given after metronidazole significantly reduced recurrence compared with placebo – about 30 per cent of women relapsed by week 12 on the live product, versus 45 per cent on placebo.9
The effect wasn’t complete, which tells you that restoring protective bacteria works best as part of a plan rather than on its own. We explain why straightforward ‘good bacteria transplants’ are still harder than they sound.
Testing properly
If antibiotics keep failing, you may be treating the wrong bacteria, sitting on a resistant strain, or dealing with a particularly tough biofilm. Many of the relevant bacteria are invisible to standard cultures, so they go untreated.
A comprehensive vaginal microbiome test shows you what is genuinely living in there, which makes the difference between guessing and treating. It is the single most useful step for anyone whose BV will not stay gone.
BV and antibiotics: frequently asked questions
Why does my BV keep coming back after antibiotics?
Usually because the antibiotic cleared the free-floating bacteria but left the biofilm and the missing protective Lactobacillus behind. Reinfection from an untreated partner and undiagnosed resistant bacteria are the other common culprits.
Can BV clear without antibiotics?
Mild BV sometimes settles on its own once the vaginal environment recovers, and biofilm disruption, herbal antimicrobials and protective-bacteria support can clear it for many people. If you are pregnant, have symptoms that won’t shift, or feel unwell, see someone in person rather than waiting it out.
Does boric acid break down BV biofilm?
Boric acid, particularly paired with a mineral-binding chelator like EDTA, has trial evidence for helping against BV and its biofilm while leaving protective bacteria alone.10 Boric acid is for vaginal use only, is never taken by mouth, and is not used in pregnancy.
Will probiotics stop my BV coming back?
The right Lactobacillus crispatus product can lower recurrence after treatment, but not every probiotic on the shelf contains a strain that actually colonises the vagina. Strain and timing matter, which is why it works best as part of a considered plan.
Should my partner be treated too?
For recurrent BV in a monogamous heterosexual couple, recent trial evidence suggests treating a male partner can roughly halve recurrence.7 It is worth raising with your practitioner if your BV keeps returning despite everything else.
Is recurrent BV a sign of something serious?
Recurrent BV is common and usually not dangerous, but because it is linked to higher STI risk and pregnancy complications, it is worth sorting properly rather than living with it. Persistent symptoms, bleeding, pelvic pain or fever deserve an in-person review.
What to do next
If antibiotics aren’t getting you anywhere, the most useful next step is to find out exactly what is going on. Get a comprehensive vaginal microbiome test, then read through our free Killing BV guides, which walk you through biofilm disruption, clearing the disruptive bacteria, and rebuilding your protective ones.
If you would rather have someone in your corner working it through with you, you can book an appointment with our practitioners. Recurrent BV is frustrating, but it is workable once you treat the whole picture rather than just the surface.
This is general information, not a substitute for personalised medical advice.
- Machado D, Castro J, Palmeira-de-Oliveira A, Martinez-de-Oliveira J, Cerca N. Bacterial Vaginosis Biofilms: Challenges to Current Therapies and Emerging Solutions. Frontiers in Microbiology. 2016;6.
- Verstraelen H, Swidsinski A. The biofilm in bacterial vaginosis: implications for epidemiology, diagnosis and treatment: 2018 update. Current Opinion in Infectious Diseases. 2019;32(1):38–42.
- Abbe C, Mitchell CM. Bacterial vaginosis: a review of approaches to treatment and prevention. Frontiers in Reproductive Health. 2023;5.
- Muzny CA, Sobel JD. The Role of Antimicrobial Resistance in Refractory and Recurrent Bacterial Vaginosis and Current Recommendations for Treatment. Antibiotics. 2022;11(4):500.
- Muñoz-Barreno A, Cabezas-Mera F, Tejera E, Machado A. Comparative Effectiveness of Treatments for Bacterial Vaginosis: A Network Meta-Analysis. Antibiotics. 2021;10(8):978.
- Sousa LGV, Pereira SA, Cerca N. Fighting polymicrobial biofilms in bacterial vaginosis. Microbial Biotechnology. 2023;16(7):1423–1437.
- Vodstrcil LA, Plummer EL, Fairley CK, et al. Male-Partner Treatment to Prevent Recurrence of Bacterial Vaginosis. New England Journal of Medicine. 2025;392(10):947–957.
- Khedkar R, Pajai S. Bacterial Vaginosis: A Comprehensive Narrative on the Etiology, Clinical Features, and Management Approach. Cureus. 2022;14(11):e31314.
- Cohen CR, Wierzbicki MR, French AL, et al. Randomized Trial of Lactin-V to Prevent Recurrence of Bacterial Vaginosis. New England Journal of Medicine. 2020;382(20):1906–1915.
- Marrazzo JM, Dombrowski JC, Wierzbicki MR, et al. Safety and Efficacy of a Novel Vaginal Anti-infective, TOL-463, in the Treatment of Bacterial Vaginosis and Vulvovaginal Candidiasis: A Randomized, Single-blind, Phase 2, Controlled Trial. Clinical Infectious Diseases. 2019;68(5):803–809.
- Braga PC, Dal Sasso M, Culici M, Spallino A. Inhibitory activity of thymol on native and mature Gardnerella vaginalis biofilms: in vitro study. Arzneimittelforschung. 2010;60(11):675–681.
- Dalabehera M, Alhudhaibi AM, Abdallah EM, et al. Natural Molecules, Nutraceuticals, and Engineered Nanosystems: A Comprehensive Strategy for Combating Gardnerella vaginalis-Induced Bacterial Vaginosis. Microorganisms. 2025;13(10):2411.
