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When you have bacterial vaginosis (BV), your protective vaginal bacteria – the lactobacilli that keep the vagina acidic and well-defended – drop away. Research shows that this loss of protection leaves you more vulnerable to catching a range of sexually transmitted infections, including HIV, herpes, the human papillomavirus, chlamydia, gonorrhoea and trichomoniasis1.
BV does not give you an STI. What it does is take away your natural front line, so that if you are exposed to an infection, you are more likely to actually catch it2. If you douche regularly, you strip out the same protection.
Here is what the evidence says, why it happens, and what you can do about it.
Does BV really increase your STI risk?
Yes. A large body of research links BV with a higher chance of picking up sexually transmitted infections (STIs). The effect is not the same for every infection, and BV is not the only thing that matters, but the pattern is consistent across studies and across different parts of the world2.
The common thread is your protective vaginal bacteria. When lactobacilli dominate, your vagina is an acidic, hostile place for invaders. When BV takes hold and disruptive bacteria move in, that defence falls away and the door is left open2.
Why don’t I catch every STI I’m exposed to?
When a virus, bacteria or fungus is introduced to your vagina, it does not automatically mean you will catch it. Plenty of people are exposed to a pathogen and never become infected, in the same way that when a cold is going around, not everyone catches it.
If you have had unprotected sex, you may have come into contact with infections that never took hold. A great deal of that comes down to your vaginal defences being in good working order at the time.
When that protection is low or absent – as it is in BV – you are more prone to catching whatever you are exposed to.
How protective bacteria defend your vagina
Protective vaginal bacteria are not passive bystanders. They actively fight off invaders using a small arsenal of biological and chemical weapons2.
- They produce lactic acid, which keeps the vagina at a low pH that most pathogens hate.
- Some strains make hydrogen peroxide and bacteriocins – natural antimicrobials that suppress disruptive bacteria.
- They crowd out invaders by occupying space and food on the vaginal wall, leaving little room for anything else to settle.
Which species are running your show makes a real difference. A community led by sturdy protectors such as Lactobacillus crispatus tends to hold the line far better than one dominated by less stable species – something we explain in our guide to community state types2.
This is not just a theory. Laboratory models that grow human cervical tissue alongside vaginal bacteria have shown directly that protective lactobacilli lower the chance of infection taking hold, while BV-type bacteria raise it – work we covered in our piece on the cervix-on-a-chip2.
What the research shows, STI by STI
HIV
This is the link with the most evidence behind it. A meta-analysis pooling 23 studies and more than 30,000 women found that BV was associated with a roughly 60 per cent higher risk of acquiring HIV1.
Part of the reason appears to be that BV draws immune cells into the vaginal lining – including the very CD4+ cells that HIV likes to infect – while also thinning the protective barrier. In other words, BV not only opens the door but rolls out a welcome mat2.
Herpes (HSV-2)
A 2026 systematic review and meta-analysis found that women with BV had a higher risk of acquiring herpes simplex virus type 2, the virus behind most cases of genital herpes3. The acidic, lactobacilli-rich environment that BV erodes seems to be part of what normally holds the virus at bay.
Human papillomavirus (HPV)
BV is associated with a higher rate of cervical human papillomavirus (HPV) infection4, and a low-lactobacilli vaginal environment is linked with the virus being slower to clear2. Because persistent high-risk HPV is what drives cervical cell changes over time, a microbiome that helps you clear the virus is worth having on your side.
Chlamydia, gonorrhoea and trichomoniasis
BV-associated bacteria have been shown to be an age-independent risk factor for chlamydia, Mycoplasma genitalium and trichomoniasis, meaning the link held regardless of how old the women were5. Separate work found that the more severe the BV, the higher the risk of catching chlamydia or gonorrhoea – a dose-response pattern that strengthens the case that BV is doing real harm to your defences6.
What this means for your vagina
Your vagina has its own immune system, and your protective bacteria are a huge part of it. When BV strips out your lactobacilli, three things happen at once: the pH rises, the chemical defences fade, and the vaginal lining becomes more inflamed and more permeable2. Every one of those changes makes it easier for an STI to get a foothold.
This is also why repeat infections so often travel together. A vagina that keeps getting BV is a vagina whose defences keep going offline, and that is exactly when other infections find their opening.
In our clinic, we focus on rebuilding protective bacteria rather than only knocking back infections, because the research shows that a vagina that can defend itself is the best defence there is.
Can treating BV lower my risk?
Restoring a protective, lactobacilli-dominant microbiome is the logical goal, and it is the foundation of how we approach BV. The aim is to clear the disruptive bacteria and their biofilm, then help your own protective species re-establish so your natural defences come back online.
That said, treating BV is not a substitute for the basics. Barrier protection such as condoms, regular STI testing and treating partners where needed all still matter, because no microbiome is a guarantee. Think of a strong vaginal community as one important layer of defence among several, not a force field.
Frequently asked questions
Is BV itself an STI?
No. BV is an imbalance of your own vaginal bacteria, not an infection passed on by a partner in the usual sense. Sexual activity can influence it, but BV is classed as dysbiosis rather than an STI.
If I have BV and a negative STI test, am I in the clear?
A negative test today is reassuring, but BV means your defences are lowered right now. The concern is about future exposures while your protective bacteria are depleted, not about an infection you have already been cleared of.
Does douching increase my risk?
Regular douching flushes out the same protective bacteria that BV depletes, and is linked with both BV and higher infection risk. As a general rule, the vagina cleans itself and does not need internal washing.
Can BV make an STI harder to clear?
For HPV, a BV-type, low-lactobacilli environment is linked with the virus persisting longer rather than clearing2. A protective microbiome appears to help your body do its housekeeping.
Will probiotics protect me from STIs?
Probiotics may help re-establish protective bacteria as part of a broader plan, but they are not a standalone shield against STIs and should not be relied on as one. The evidence is about restoring the microbiome, not replacing safe-sex basics.
How do I know what my microbiome is actually doing?
Symptoms only tell you so much, and plenty of people have low lactobacilli without obvious signs. A proper test shows which bacteria are present and whether your protective species are in charge.
What to do next
If you keep getting BV, the most useful thing you can do is understand what is happening in your own vagina and treat the root of it, rather than chasing one infection after another.
- Learn the early warning signs of BV so you can act quickly when it flares.
- Consider a comprehensive vaginal microbiome test so you know exactly which bacteria are present.
- If BV keeps coming back, our Killing BV treatment program walks you through restoring your protective bacteria step by step.
- For tailored help, you can book a consultation with one of our practitioners.
You can also ask Aunt Vadge’s Assistant, the chat widget in the bottom left of your screen, to point you in the right direction.
This article is general information and not a substitute for personalised medical advice. If you are worried about BV or a possible STI, please see a qualified practitioner.
References
1. Atashili J, Poole C, Ndumbe PM, Adimora AA, Smith JS. Bacterial vaginosis and HIV acquisition: a meta-analysis of published studies. AIDS. 2008;22(12):1493–1501.
2. Gilbert NM, Ramirez Hernandez LA, Berman D, Morrill S, Gagneux P, Lewis AL. Social, microbial, and immune factors linking bacterial vaginosis and infectious diseases. Journal of Clinical Investigation. 2025;135(11):e184322.
3. Whitt TN, Heath A, Hill DJ, Brubaker DK, Farr Zuend C. Risk of HSV-2 acquisition among women with bacterial vaginosis: systematic review and meta-analysis. Viruses. 2026;18(3):330.
4. Gillet E, Meys JF, Verstraelen H, Bosire C, De Sutter P, Temmerman M, Vanden Broeck D. Bacterial vaginosis is associated with uterine cervical human papillomavirus infection: a meta-analysis. BMC Infectious Diseases. 2011;11:10.
5. Shipitsyna E, Khusnutdinova T, Budilovskaya O, et al. Bacterial vaginosis-associated vaginal microbiota is an age-independent risk factor for Chlamydia trachomatis, Mycoplasma genitalium and Trichomonas vaginalis infections in low-risk women, St. Petersburg, Russia. European Journal of Clinical Microbiology & Infectious Diseases. 2020;39(7):1221–1230.
6. Allsworth JE, Peipert JF. Severity of bacterial vaginosis and the risk of sexually transmitted infection. American Journal of Obstetrics and Gynecology. 2011;205(2):113.e1–113.e6.
