Can a Man Give a Woman BV? Partners and the 2025 Trial

Yes, in the way that matters: men do not get bacterial vaginosis, but the bacteria behind it live on the penis and in the urethra of some men, pass between partners during sex, and in a 2025 trial in which the man was given antibiotics alongside the woman's course, BV's return within 12 weeks fell from 63% to 35%.² The NHS does not class BV as a sexually transmitted infection, since women who have never had sex get it too, but says sex can trigger it or pass it on.¹ Across 43 studies, a new or additional male partner raised a woman's risk of BV 1.6-fold, a female partner 2-fold, and consistent condom use lowered it.³ This is the partner page of the Wellgard guide to what causes BV.

Sources checked on 29 October 2026.

Can a man give a woman BV?

BV is not one germ that jumps from person to person. It is the loss of the lactobacilli that normally dominate the vagina and hold its pH at around 3.5, and the overgrowth of anaerobic bacteria in their place.⁴ What a man can pass on is that crowd. In monogamous couples where the woman had BV, the bacteria on the man's penile skin and in his urethra matched his partner's vagina more closely than they matched other women with BV, and specific BV-associated species were shared by both halves of the couple.⁵ Among 165 uncircumcised men in Uganda, men with dense, anaerobe-rich penile communities were more likely to have a partner with BV.⁶ In a Kenyan cohort of 168 couples in which the woman started without BV, 31% developed it within a year, and the bacteria sampled from the man's penis at the start predicted which women would, with 77% accuracy.⁷ More than half of those new cases arrived six to twelve months after he was swabbed.

Sex adds a second effect that has nothing to do with his bacteria: semen is alkaline and lifts the vaginal pH for hours, which is why the NHS lists a fishy smell "particularly after sex" as the first sign of BV.¹

Do men get BV? What the penis carries

No. There is no vagina to be inflamed, no male test and no male symptom; a man carrying BV-associated bacteria feels nothing. The bacteria sit on the skin under the foreskin and inside the urethra, more often in uncircumcised men: in the Kenyan couples, BV developed in 37% of partners of uncircumcised men and 26% of partners of circumcised men.^{6, 7} This is his skin flora for a time, not an infection he has caught; "carrier" overstates it.

What is the male version of BV? There is not one. The male conditions a reader may be thinking of are balanitis, soreness and redness of the head of the penis, one cause of which is thrush, and urethritis, a discharge or pain when peeing that needs a sexual health clinic because it is usually an STI.^{8, 15}

Is BV an STI, and did he cheat?

BV is not an STI, and getting it says nothing about fidelity. In a 12-month study of 139 women after a course of antibiotics, BV returned in 58%, and staying with the same partner raised the risk of its return.⁹ In a trial of 450 women, sex with the same partner after treatment nearly doubled the chance of recurrence (hazard ratio 1.9).¹⁰ BV with one faithful partner that clears when apart and returns when together is what a shared pool of bacteria passing back and forth would produce. The Ugandan study did find denser BV-type communities in men with two or more partners outside marriage, but that describes exposure across a population, not a test you can run on one relationship.⁶

A new partner for either of you is a reason for both to have an STI screen, and BV makes the vagina less acidic and raises the chance of catching an STI.¹ If the smell and discharge do not match BV, is it thrush, BV or something else? runs through what else it could be, including trichomoniasis, which is an STI.

Do male partners need treatment? The 2025 trial

For twenty years the answer was no, because every trial had given men tablets alone. A 2016 Cochrane review of seven trials and 1,026 couples found that giving the man antibiotics made no difference to the woman's outcome at the end of her course or to whether BV returned, and gave the men more side effects.¹¹ A 2021 trial of 214 couples gave the men oral metronidazole or placebo: the woman's treatment failed in 81% and 80%.¹²

The 2025 trial in the New England Journal of Medicine changed the regimen rather than the idea. In 164 couples, the man took oral antibiotics and applied an antibiotic cream to the skin of the penis while the woman had her course. BV returned within 12 weeks in 24 of 69 women (35%) whose partners were treated, against 43 of 68 (63%) treated alone, and the trial was stopped early because the difference was so clear.² It was open-label and it is one trial; a 2026 network meta-analysis pooling the partner studies put the reduction in recurrence at 24% with moderate certainty.¹³

Does my boyfriend need antibiotics if I have BV? For a first episode, UK practice treats the woman only; the NHS page mentions a course for a partner only where that partner has a vagina.¹ If BV keeps coming back, ask at a sexual health clinic whether partner treatment on the 2025 pattern is available; he will need to attend. The medicines are prescription antibiotics; there is nothing to buy for him. How is BV treated in the UK? covers the woman's side, and why do I keep getting BV? puts partner treatment in order with the other triggers.

How long can a man carry BV bacteria?

No study has timed it. What the cohort studies show is that the penile community is stable enough to predict a partner's BV six to twelve months later, so weeks to months is a fair reading.⁷ The 2025 trial shows the other side: a combined course for both partners changed the woman's outcome over the following three months.² Between those two facts sits the advice most clinics give: condoms for a few weeks after her course, which also tests whether semen is her trigger, since consistent condom use goes with a lower BV risk across studies.^{3, 10}

Should I tell my partner?

Yes. Should he be worried? Not for his own health: he has no infection, no symptoms and nothing to test. His semen raises your pH for a few hours, so a flare after sex is expected. If BV recurs, the only partner treatment with trial support involves him taking a course too.²

If your partner is a woman, the picture is more direct: in a study of women who have sex with women, 25% had BV; smears matched in 55 of 58 monogamous couples (95%), and both partners had BV in 28%. The NHS says a partner who is a woman may need a course alongside you.^{1, 14}

What we don't know

How long a man carries the bacteria: no study has timed it.⁷ Whether the 2025 result holds outside one open-label trial of monogamous couples that was stopped early.² Whether it is particular species passing back and forth or the disruption of sex itself, semen included, that resets the vagina.^{5, 6} Whether circumcision changes the picture for UK couples: the cohorts that measured it were in Uganda and Kenya.^{6, 7}

Frequently asked questions

Can a man catch BV from a woman?

He cannot develop BV, but he can pick up the bacteria on the penis and in the urethra and pass them back.^{5, 6, 7}

Should we both take antibiotics at the same time?

Only on prescription, after a clinic has assessed you both. In the 2025 trial the courses ran together and his included a cream for the penile skin.²

Can a man be tested for BV?

No. There is no male BV test; a man with discharge, soreness or pain when peeing needs an STI and balanitis check at a sexual health clinic.^{8, 15}

Does having BV mean my partner has an STI?

No. BV is not an STI and can arise with no partner at all. A new partner, or yellow-green, frothy or sore discharge, is the reason to test for STIs.¹

Sources

1. NHS. Bacterial vaginosis. Page last reviewed 19 June 2026. nhs.uk/conditions/bacterial-vaginosis.
2. Vodstrcil LA, et al. Male-partner treatment and recurrence of bacterial vaginosis. New England Journal of Medicine, 2025. Open-label randomised trial, 164 couples; publicly funded. PubMed 40043236.
3. Fethers KA, et al. Sexual risk factors and bacterial vaginosis. Clinical Infectious Diseases, 2008. Systematic review and meta-analysis, 43 studies. PubMed 18947329.
4. O'Hanlon DE, et al. Vaginal pH and microbicidal lactic acid when lactobacilli dominate the microbiota. PLoS One, 2013. Observational study, 56 women; two authors work for a company developing vaginal products. PubMed 24223212.
5. Zozaya M, et al. Bacterial communities in penile skin, male urethra, and vaginas of heterosexual couples. Microbiome, 2016. Cross-sectional sequencing study of monogamous couples. PubMed 27090518.
6. Liu CM, et al. Penile microbiota and female partner bacterial vaginosis in Rakai, Uganda. mBio, 2015. Cross-sectional study, 165 uncircumcised men. PubMed 26081632.
7. Mehta SD, et al. The microbiome composition of a man's penis predicts incident bacterial vaginosis in his female sex partner. Frontiers in Cellular and Infection Microbiology, 2020. Prospective cohort, 168 couples, 12 months. PubMed 32903746.
8. NHS. Balanitis. Page last reviewed 30 May 2023. nhs.uk/conditions/balanitis.
9. Bradshaw CS, et al. High recurrence rates of bacterial vaginosis 12 months after oral metronidazole therapy. Journal of Infectious Diseases, 2006. Prospective cohort, 139 women, 12 months. PubMed 16652274.
10. Bradshaw CS, et al. Recurrence of bacterial vaginosis, posttreatment sexual activities and hormonal contraceptive use. Clinical Infectious Diseases, 2013. Randomised trial, 450 women, six months. PubMed 23243173.
11. Amaya-Guio J, et al. Antibiotic treatment for the sexual partners of women with bacterial vaginosis. Cochrane Database of Systematic Reviews, 2016. Cochrane review, seven randomised trials, 1,026 participants; four trials industry-funded. PubMed 27696372.
12. Schwebke JR, et al. Treatment of male sexual partners of women with bacterial vaginosis. Clinical Infectious Diseases, 2021. Double-blind randomised trial, 214 couples. PubMed 33383580.
13. Gardella B, et al. Rethinking prevention of recurrent bacterial vaginosis. Journal of Lower Genital Tract Disease, 2026. Network meta-analysis of randomised trials. PubMed 42611724.
14. Marrazzo JM, et al. Characterization of vaginal flora and bacterial vaginosis in women who have sex with women. Journal of Infectious Diseases, 2002. Cross-sectional study, 326 women. PubMed 12001048.
15. NHS. Urethritis. Page last reviewed 10 May 2023. nhs.uk/conditions/non-gonococcal-urethritis.

Spotted something out of date? Email support@wellgard.co.uk with the page address and the sentence.

This article is general information, not medical advice. See a GP or sexual health clinic for a first episode of BV, for any discharge in pregnancy, after a new partner, and whenever treatment has not worked.