A man can't actually get BV. That's the part the question skips right over. He has no vagina and no vaginal microbiome, so there's nothing for him to catch and hold onto for some set number of days.
What he can carry is the bacteria behind it. And that matters far more than any timeline. In 2025, a major trial found that treating the male partner cut BV recurrence from 63% to 35% [1].
So the real question was never how long he's contagious. It's what he's quietly carrying, and whether that's been undoing your treatment all along.
Men don't get BV, but they aren't bystanders
Bacterial vaginosis happens when the protective Lactobacillus bacteria that keep the vagina acidic get outnumbered by anaerobic bacteria. Because men don't have that ecosystem, they're never diagnosed with BV.
Their genitals still host bacteria, though. Penile skin and the urethra carry their own microbial community, and that community can include the same anaerobes tied to BV in women [3][5]. So "carrier," in a sense, yes. "Patient," no.
So what is he actually carrying?
Studies of the penile microbiome have found BV-associated bacteria, including organisms like Gardnerella, living on penile skin, under the foreskin, and in the urethra [5][3]. Some men's urine carries them too, which points to the urethra as a reservoir and not only the skin [3].
He usually feels none of it. That silence is part of the problem. If nothing itches or burns, why would he think he's part of the loop?
There's also no routine swab that diagnoses "BV in a man," because he doesn't have the condition to diagnose [4]. It won't show up on a standard STI panel either [4]. That's a big reason the newest approach treats partners without testing them first [1][4].
This is also why circumcision keeps surfacing in the research. It's linked to fewer of these anaerobic bacteria on the penis and to lower BV risk in female partners [5].
Is there a clock on it?
The honest answer to "how long" is unsatisfying but freeing. There's no tidy number of days, because carriage isn't a timed illness with a start and a finish. It's colonization, plain and simple.
Those bacteria can live on the skin and in the urethra, persist over time, and get passed back and forth during sex [3]. So it behaves less like a cold he shakes off by Friday and more like a shared houseplant the two of you keep re-watering.
None of that means it's permanent, though. A course of treatment can clear his share of the bacteria. That's exactly what the newest research set out to test [1].
Why this matters: the recurrence trap
If you have watched BV come back again and again, the reason may not be you at all. More than half of women see BV return within three to six months of finishing treatment [2][3].
One long-suspected reason is reinfection. You treat your BV, feel better, have sex with an untreated partner, and the same bacteria get reintroduced [3]. Semen plays a part too. It can briefly nudge vaginal pH upward, and it may carry more of those bacteria in [3].
To be fair, reinfection is one driver among several. Stubborn bacterial films and a slow comeback of protective Lactobacillus both play a role too [3][2]. Partners are simply the piece that got ignored for a long time.
The 2025 study that shifted the conversation
For years this reinfection theory stalled, because earlier trials that treated male partners didn't lower recurrence [4]. Then a 2025 randomized trial in the New England Journal of Medicine changed the picture [1].
When male partners took a week of oral and topical antibiotics alongside the woman's standard treatment, BV returned in 35% of women, compared with 63% when only the woman was treated [1]. The study followed 164 couples over 12 weeks [1]. The regimen used both a pill and a skin cream to reach the urethra and the skin at once, and the benefit was clear enough that the trial was stopped early [1].
What this does and doesn't mean for you
Read the fine print before you overhaul everything. This was a single open-label trial in monogamous couples, and several partner-treatment studies before it had come up empty [4][1]. The treated men also reported side effects like nausea, headache, and a metallic taste [1]. It's a real regimen with real tradeoffs, not a casual add-on.
This matters most if you get BV over and over in a steady relationship [1][4]. For a one-off episode, treating your partner isn't the expected move [4].
US specialists reviewing the findings in 2025 noted that big questions remain about how widely the results apply, and that partner treatment isn't yet standard practice in the United States [4]. It's also clinician-directed. The topical part is a prescription a provider manages, not something to recreate at home [1][4].
What you can actually do on your side
If BV keeps returning, the highest-value move is a direct conversation with your provider about whether partner treatment fits your relationship and history [4]. That's now a legitimate, evidence-backed thing to ask for.
Come to that appointment with specifics. How often BV returns, how soon after sex, and whether past treatments held. That context helps your provider decide if partner treatment is worth trying [4].
Condoms also act as a barrier to that exchange, and consistent use is linked to lower BV risk [3]. Skipping douches and harsh washes helps too. Both strip the acidic balance you're trying to protect.
And supporting your own environment matters daily. Lactic acid helps keep the vagina at its naturally acidic pH, which is part of why it appears in gentle formulas like Neycher's Boric Acid Complex.
For years the standard advice left your partner out of it entirely. The bacteria never agreed to those terms. They move between two people, so the smartest plan finally does too.
When to see a healthcare provider
If you have recurring symptoms, unusual discharge, or a persistent odor, get tested rather than guessing. A quick swab can confirm what's going on and rule out other causes. Beyond the symptoms, ongoing BV is linked to risks in pregnancy and to other infections, so it's worth taking seriously [2]. And if recurrence is your pattern, that's the moment to bring up partner treatment with someone who can order it.
Sources
- 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. PMID: 40043236. https://pubmed.ncbi.nlm.nih.gov/40043236/ (doi:10.1056/NEJMoa2405404)
- Bradshaw CS, Plummer EL, Muzny CA, et al. Bacterial vaginosis. Nat Rev Dis Primers. 2025;11(1):43. PMID: 40537474. https://pubmed.ncbi.nlm.nih.gov/40537474/ (doi:10.1038/s41572-025-00626-1)
- Vodstrcil LA, Muzny CA, Plummer EL, Sobel JD, Bradshaw CS. Bacterial vaginosis: drivers of recurrence and challenges and opportunities in partner treatment. BMC Med. 2021;19(1):194. PMID: 34470644. https://pmc.ncbi.nlm.nih.gov/articles/PMC8411528/ (doi:10.1186/s12916-021-02077-3)
- Yazdy GM, Workowski KA, Ghanem KG, et al. Male partner treatment and the potential sexual transmission of bacterial vaginosis: considerations for patient counseling and clinical application in the United States. Am J Obstet Gynecol. 2025;234(3):606-612. PMID: 41213492. https://pubmed.ncbi.nlm.nih.gov/41213492/ (doi:10.1016/j.ajog.2025.11.001)
- Onywera H, Williamson AL, Ponomarenko J, Meiring TL. The Penile Microbiota in Uncircumcised and Circumcised Men: Relationships With HIV and Human Papillomavirus Infections and Cervicovaginal Microbiota. Front Med (Lausanne). 2020;7:383. PMID: 32850898. https://pmc.ncbi.nlm.nih.gov/articles/PMC7406686/ (doi:10.3389/fmed.2020.00383)
This article is for educational purposes only and is not medical advice. Talk with a qualified healthcare provider about diagnosis and treatment options for your situation.
