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Been diagnosed with bacterial vaginosis (BV), or just suspicious because of a fishy-smelling vagina? You are not alone. BV is the most common cause of unusual discharge and odour in women and people with vaginas of reproductive age, and millions are diagnosed every year.1
That fishy smell is the classic sign of BV, but a couple of sexually transmitted infections (STIs) can cause it too. Before you assume anything, get properly tested – a full STI screen with your healthcare provider, plus a comprehensive vaginal microbiome test to see exactly what is growing down there.
And BV is treatable, even when it has come back again and again. The people who get lasting results usually do more than a single round of antibiotics – they also rebuild the protective bacteria that keep the vagina in balance. This guide walks you through why BV smells the way it does, how to be sure that is what you are dealing with, and what actually works to clear it for good.
Why does my vagina smell like fish?
The fishy smell comes from the bacteria themselves. When disruptive bacteria such as Gardnerella vaginalis and friends take over, they produce smelly compounds called amines – including putrescine and cadaverine, which are exactly as charming as they sound.1 These amines become more volatile (more sniffable) when the vagina is less acidic, which is why the smell often gets stronger.
That is also why so many people notice the odour right after sex or around their period. Semen is alkaline and menstrual blood nudges the pH up, so both can briefly switch the smell on. If you want the detail on which bacteria make which symptoms, we have a whole piece on Gardnerella byproducts and the symptoms they cause.
The discharge that comes with BV is usually thin, greyish or milky white, and there is often more of it than usual. BV is not usually itchy or sore – if you have a lot of itch, burning or soreness, something else may be going on, which brings us to the next question.
Is it definitely BV, or something else?
A fishy smell points strongly to BV, but it is not the only cause, and this is exactly why testing matters. A few other things can produce odour or discharge:
- Trichomoniasis, an STI caused by a tiny parasite, can give a frothy, smelly discharge.
- Aerobic vaginitis (AV) is a different kind of imbalance involving gut-type bacteria. It looks a lot like BV but needs a different approach – see aerobic vaginitis vs BV.
- A forgotten tampon (it happens to the best of us) can create a powerful smell all on its own.
- A yeast infection usually smells fairly neutral and is mostly about itch and a thick white discharge, so a fishy smell makes yeast less likely – though you can have both at once.
Because the symptoms overlap so much, guessing is a poor strategy. Two people with an identical fishy smell can need completely different treatment, and treating the wrong thing is a fast track to the merry-go-round of recurrence.
Getting a thorough vaginal microbiome test
Testing is important for two reasons. First, some STIs can quietly damage your reproductive system if they are left untreated, so it is worth ruling them out even if you are fairly sure you could not have one. Second, knowing exactly which bacteria are involved tells you how to treat them.
STIs cannot be sorted out at home – they need a clinician – but BV very much can be treated at home once you know that is what you are dealing with. A standard swab or culture only looks for a handful of things, and it can miss the fuller picture. Sometimes bacteria that a basic culture or PCR does not look for are part of the problem – you might have aerobic vaginitis bacteria alongside the BV-related ones, for example.
This is why we point people towards a comprehensive at-home test that maps the whole microbiome, rather than a yes-or-no BV result. If you have already had tests that came back muddled or contradictory, our piece on why vaginal tests disagree explains what is going on.
What is BV, really?
BV is an imbalance in the community of bacteria living in your vagina. In a well-functioning vagina, protective Lactobacillus species – especially Lactobacillus crispatus – dominate, producing lactic acid that keeps the environment acidic and inhospitable to troublemakers.1
In BV, those protective lactobacilli drop away and a mixed crowd of disruptive bacteria moves in – Gardnerella, Prevotella, Fannyhessea (formerly Atopobium) and others. The pH rises, the protective acid disappears, and the smelly amines build up. Researchers describe the vaginal microbiome in community state types, and the one packed with these disruptive bacteria instead of lactobacilli is the BV-associated pattern.1
One species worth knowing about is Lactobacillus iners. It is a lactobacillus, so it looks protective on paper, but it is a fence-sitter: it tends to hang around during the wobble between balance and BV, and a vagina stuck in an L. iners-dominant state can slide back into trouble, especially after repeated antibiotics.2 Your genes also play a part in which bacteria settle in, as we cover in how your genes shape your vaginal microbiome.
The biofilm – why your BV keeps coming back
If you have treated BV and watched it march straight back, you have met the biofilm. Recurrent BV – the kind that returns no matter what you do – is held together by a sticky bacterial biofilm made largely by Gardnerella vaginalis.
A biofilm is not just free-floating bacteria. The bacteria build themselves a slimy coating they live inside, glued to the vaginal wall, which displaces your protective bacteria and shields the colony. It is not only Gardnerella in there either – other disruptive bacteria climb aboard and hide, and the more species join, the tougher the biofilm becomes.
This is the whole reason BV is so stubborn. The biofilm is built to resist, including standing up to high-dose antibiotics, which is precisely why a single course so often fails. More than half of people treated with standard antibiotics see their BV return within twelve months, and the biofilm is a big part of why.1 Clearing BV for good means dealing with the biofilm, not just the bacteria floating around it.
What causes BV, and why the balance tips
BV is not a sign you are dirty, and it is not caused by being ‘unclean’ – if anything, over-washing makes it worse. The balance tips for all sorts of reasons, and often more than one is in play at once:
- Sex, and especially a new partner. BV-associated bacteria can be passed between partners, and a new partner can usher unwelcome guests in. Alkaline semen also nudges the pH the wrong way.
- Douching and ‘feminine washes’, which strip out protective bacteria and disturb the pH. Your vagina cleans itself – it does not need help from a bottle.
- Low oestrogen, which thins the vaginal tissue and starves protective lactobacilli of the glycogen they feed on. This is common after birth, while breastfeeding, and around menopause.
- Hormonal contraception in some people – for example, hormonal IUDs can tip some women into BV.
- Smoking, which is consistently linked to a less protective microbiome.
- A bacterial reservoir elsewhere – in the gut, or in a partner – that keeps reseeding the vagina after each treatment.
Not all BV is a standalone vaginal event, either. Sometimes it is the end result of something else going on in the body – low oestrogen, a gut issue, a systemic health condition – rather than the root problem itself. That distinction matters enormously when BV will not stay away.
In our clinic, the people we see with stubborn, recurrent BV almost always have something underneath driving it – a hormone shift, a gut picture, a partner reservoir – and once we find and address that, the body provides the right conditions the vaginal environment needs to rebuild its own protective bacterial colonies.
What BV does to your vagina and wider health
Day to day, BV is mostly an annoyance – the smell, the discharge, the self-consciousness. But because it leaves the vagina without its protective acid barrier, it has knock-on effects worth taking seriously.
A vagina low in protective lactobacilli is more vulnerable to STIs, including HIV, and to pelvic inflammatory disease if disruptive bacteria travel upward.1 In pregnancy, BV is linked to a higher risk of preterm birth and miscarriage – studies put the increase at roughly two to seven times depending on how early it is present – which is why BV in pregnancy is always worth flagging to your maternity team rather than treating yourself.1
None of this is meant to frighten you. It is simply why getting on top of BV properly – and keeping your vagina in a protective state – is worth the effort, beyond just chasing the smell away.
How BV is treated
There is no single magic bullet, and anyone who tells you otherwise is selling something. Lasting results come from a combination: knock back the disruptive bacteria, break down the biofilm, and rebuild the protective lactobacilli so they can hold the territory.
Antibiotics
The standard first-line treatment is an antibiotic – usually metronidazole or clindamycin, as a tablet or a vaginal gel. For a one-off bout of BV, this often works nicely, and it is a perfectly reasonable place to start.
The trouble is recurrence. Antibiotics knock down the disruptive bacteria but do not rebuild the protective ones, and they struggle to penetrate the biofilm – so for a lot of people the BV comes back within weeks or months. If you are reading this, there is a good chance your first or second round did not hold. That is not a personal failing – it just means antibiotics alone are not enough for you, and the goal needs to widen.
Treating the biofilm and rebuilding protective bacteria
This is where lasting results are won. The approach that works targets the biofilm directly, removes the disruptive bacteria hiding inside it, and then reseeds and feeds the protective lactobacilli so they can take back the wall. It is slower than a single antibiotic course, but it is the part that actually keeps BV from returning.
This is precisely the method behind our Killing BV treatment program – a structured plan that combines biofilm-disrupting and antimicrobial support with the work of rebuilding a protective microbiome, taking your body, hormones and history into account rather than treating the vagina in isolation. There is also a free version of the approach in our treat BV guides if you would rather work through it yourself.
Should my partner be treated?
This is a real shift in thinking. For years, treating male partners was considered pointless. Then in 2025, a randomised trial showed that treating a woman’s regular male partner – with both an oral antibiotic and a topical cream – significantly cut the rate of BV coming back, compared with treating the woman alone.3
This supports something we have long suspected in recurrent cases: if a partner is quietly carrying the same bacteria, they can reseed you after every treatment, and you can chase your tail forever. If your BV keeps returning, it is worth having a conversation with your clinician about treating your partner too. Partner treatment is still being worked into mainstream guidelines, so it may be a newer idea to whoever you see.
Probiotics and live biotherapeutics
Putting protective bacteria back is a logical step, and the science is catching up with the idea. In a trial of a vaginal Lactobacillus crispatus live biotherapeutic – essentially a pharmaceutical-grade probiotic – given after antibiotics, BV recurrence at twelve weeks was 30 per cent, compared with 45 per cent on placebo.4 Not a cure on its own, but a meaningful boost when paired with clearing the biofilm first.
Everyday oral and vaginal probiotics vary enormously in quality and strain, and most off-the-shelf products are not the strains that actually colonise the vagina. If your microbiome is stuck in that L. iners-dominant fence-sitting state, a more targeted approach makes sense – see how to shift an L. iners-dominant vagina. We also keep an eye on the experimental end of this, like vaginal microbiota transplants, which are promising but not ready yet.
Home remedies and natural approaches
Plenty of home remedies get passed around for BV, and they range from quite useful to actively counterproductive. Here is an honest read on the popular ones, with the detail behind each:
- Apple cider vinegar and hydrogen peroxide – sometimes used to alter the vaginal environment, but both can irritate and neither is a reliable cure. We do not recommend routine douching with anything.
- Vitamin C and vitamin D – there is some research interest here, particularly where a deficiency exists.
- Folate – the real-food form matters more than synthetic folic acid.
- Boric acid – sometimes used to help with biofilms, but with firm caveats: it is for vaginal use only, never swallowed, and it is not safe in pregnancy. See can boric acid disrupt BV biofilms?
- Cranberry – popular for urinary health, but the evidence for BV specifically is thin.
The honest summary is that natural and home approaches can play a real supporting role, but for stubborn or recurrent BV they work best as part of a structured plan, not as random single fixes thrown at the wall. If you are weighing up your options, we compare natural versus prescription BV treatments in more detail.
Preventing BV from coming back
Once you have cleared BV, a few habits really help keep your protective bacteria in charge:
- Skip the douches, scented washes and ‘feminine hygiene’ products. Warm water on the vulva is plenty.
- Use condoms with a new partner while your microbiome settles, and consider partner treatment if BV keeps returning.
- Address low oestrogen if that is part of your picture – particularly postpartum, while breastfeeding, or around menopause.
- Look after your gut, since it can act as a bacterial reservoir.
- Retest if symptoms return rather than guessing, so you treat what is actually there.
Frequently asked questions
Will BV go away on its own?
Sometimes a mild bout settles by itself as the microbiome rebalances. But BV that has set up a biofilm tends to dig in, and persistent or recurrent BV usually needs active treatment to clear properly.
Can I treat BV at home?
Yes, once you are confident BV is what you have and you have ruled out STIs. Home treatment works best as a structured plan that tackles the biofilm and rebuilds protective bacteria, rather than a single remedy.
Why does my BV keep coming back?
Usually because of a biofilm that antibiotics cannot fully clear, protective bacteria that were never rebuilt, or an ongoing driver such as low oestrogen, a gut reservoir or an untreated partner. Recurrent BV is a signal to look underneath, not just retreat the surface.
Does BV smell worse after sex or my period?
Yes. Semen and menstrual blood both raise the vaginal pH, which makes the smelly amines more noticeable. A stronger fishy smell at those times is a classic BV pattern.
Is BV a sexually transmitted infection?
BV is not classed as an STI, but it behaves a bit like one. Sex and new partners can trigger it, the associated bacteria can be exchanged between partners, and treating a regular partner can reduce recurrence.
Can men get BV?
Men do not get BV as such, but they can carry BV-associated bacteria on and around the penis without symptoms, and act as a reservoir that reseeds a partner. This is the thinking behind partner treatment in recurrent cases.
Is BV dangerous in pregnancy?
BV in pregnancy is linked to a higher risk of preterm birth and miscarriage, so it is worth taking seriously. If you are pregnant, do not self-treat – flag any symptoms to your maternity team, and avoid boric acid entirely, as it is not safe in pregnancy.
What is the difference between BV and a yeast infection?
BV is a bacterial imbalance with a thin, fishy-smelling discharge and little itch. A yeast infection is a fungal overgrowth with a thick, fairly odourless discharge and a lot of itch. They are treated completely differently, and you can occasionally have both, which is why testing helps.
Do I need to treat BV if I have no symptoms?
Outside pregnancy, asymptomatic BV does not always need treating, and some cases resolve on their own. In pregnancy, or if you are having a gynaecological procedure, it is more likely to be worth treating – discuss it with your clinician.
What to do next
If you have a fishy smell and have not been tested, start there: a full STI screen, plus a test that maps your whole vaginal microbiome so you know exactly what you are working with. If you already know it is BV and it keeps returning, the next move is a plan that deals with the biofilm and rebuilds your protective bacteria – whether you follow our free guides or the full Killing BV program.
If you would like a hand making sense of your results, you can ask Aunt Vadge’s Assistant – the chat widget in the bottom left of your screen – or book an appointment with one of our practitioners to build a plan around your particular situation.
This article is general information, not a substitute for personalised medical advice. If your symptoms are severe, you are pregnant, or things are not improving, please see a healthcare provider.
- Bradshaw CS, Plummer EL, Muzny CA, Mitchell CM, Fredricks DN, Herbst-Kralovetz MM, Vodstrcil LA. Bacterial vaginosis. Nat Rev Dis Primers. 2025;11(1):43.
- Zheng N, Guo R, Wang J, Zhou W, Ling Z. Contribution of Lactobacillus iners to vaginal health and diseases: a systematic review. Front Cell Infect Microbiol. 2021;11:792787.
- Vodstrcil LA, Plummer EL, Fairley CK, et al. Male-partner treatment to prevent recurrence of bacterial vaginosis. N Engl J Med. 2025;392(10):947–957.
- Cohen CR, Wierzbicki MR, French AL, et al. Randomized trial of Lactin-V to prevent recurrence of bacterial vaginosis. N Engl J Med. 2020;382(20):1906–1915.
