Bacterial vaginosis (BV) is the most common vaginal condition in women aged 15-44, and although it’s not technically a sexually transmitted infection (STI), sex plays a big role. Which begs the question: since it takes two to tango, what is men’s role in bacterial vaginosis? Would treating a male partner for BV reduce your risk of developing it?  

Experts still aren’t exactly sure what causes bacterial vaginosis, but there’s evidence that men play a part in transmission to their female sex partners during sex. Keep reading to learn more about the relationship between BV, sex, and male partner treatment.

The link between sex and BV 

Although bacterial vaginosis isn’t classified as an STI, sex — especially unprotected sex — can influence the vaginal microbiome and increase your risk of BV. 

Studies have shown that sex can change the vaginal pH and introduce foreign bacteria, increasing the likelihood of symptomatic bacterial vaginosis. A healthy vaginal pH is slightly acidic to keep bad bacteria or other pathogens from growing. Semen, on the other hand, has an alkaline pH. The presence of semen in the vagina can shift your vaginal pH and allow pathogens to colonize. 

Contrary to popular belief, men also have microbiomes — specifically, penile and semen microbiomes. Some studies also show that although men can’t have bacterial vaginosis, they can carry BV-associated bacteria (like Gardnerella) and pass it on to people with vaginas during sex. Other research has shown that using a condom not only prevents STIs but also reduces the recurrence of BV.

Interestingly, the same is true for same-sex couples with vaginas. Women in same-sex relationships can also pass BV to their partners. Research even shows that women who have female sex partners are more likely to have bacterial vaginosis compared to women who only have sex with men. 

This is to say that both female and male sex partners can play a huge role in recurrent bacterial vaginosis, and a 2022 report by the Centers for Disease Control and Prevention (CDC) recognized that BV can be sexually transmitted. It’s still not technically an STI, but this can change the way we think about and treat BV. So what do we know about male partner treatment to prevent recurrent bacterial vaginosis?

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Do men need to be treated for BV?

Since research shows that men can spread BV-associated bacteria to women during sex, will male partner treatment prevent bacterial vaginosis in women? Male partner treatment involves treating the sexual partner with antibiotics to prevent reinfection of BV-causing organisms. While this concept seems logical, the evidence is still inconclusive.

It's important to note that studies conducted in the last few decades have shown mixed results when it comes to reducing bacterial vaginosis in women through male partner treatment alone. 

While sex can be a trigger for bacterial vaginosis, other factors can contribute to flare-ups as well. Antibiotic use, smoking, douching, and having had BV in the past are all risk factors for BV. So while male partner treatment might make post-sex BV less likely, it won't get rid of the problem altogether. 

Getting male partners on board with BV treatment can be also tricky, as the bacteria associated with BV on the penis often don't cause symptoms in men, which can make it difficult to convince them to undergo treatment. Acceptance of partner treatment may depend on the dynamics of the relationship, with long-term committed relationships showing higher rates of acceptance.

Nevertheless, researchers are still looking into whether treating BV in men can reduce BV recurrence in women. A pilot study of 34 couples showed promising results and found that male partner treatment greatly decreased the levels of BV-associated bacteria in men. And even though this was a population with an increased risk of BV recurrence, only 17% of women had BV symptoms by 12 weeks after treatment. 

So, when it comes to BV and sex, there's a lot we still don't know. Studies that looked at male partner treatment to prevent BV from coming back had mixed results. It's frustrating, but it doesn't mean that partner-acquired BV isn't a real thing. It just means that we need more research to figure out what's going on and how to best treat it. 

The good news is that some male partner treatment trials are happening right now that look promising. In the meantime, one way to reduce your risk of developing BV after sex is to use a condom or dental dam, and look after the health of your vaginal microbiome overall.


Why do I get BV after sex?

There are a few reasons why you might get BV after sex. Firstly, sexual activity can introduce new bacteria into the vaginal microbiome, whether that bacteria comes from the fingers, penis, mouth, sex toy, or another vagina. Research shows that sex with both men and women can increase your chances of developing BV. Secondly, having unprotected sex with men can alter your natural pH. Normally, a healthy vagina has a slightly acidic pH, but semen is more alkaline, which can make it easier for bad bacteria or fungi to grow, leading to things like yeast infections or BV. The good news is that using condoms and dental dams can help lower your chance of getting bacterial vaginosis from sex.

Can a man give BV to a woman?

Researchers are still trying to figure out what causes BV, but evidence shows that BV can indeed be transmitted during sex. Men can’t get BV themselves, but they can carry BV-associated bacteria in their penile and semen microbiomes and spread it to their female partners during sex. 

Should my boyfriend be treated for BV?

We don’t know yet if treating a male partner for BV can reduce your risk of developing it. Researchers have been looking into whether male partner treatment can reduce BV recurrence in women, and while some pilot studies have been promising, the evidence is still inconclusive. If you find that you keep getting BV after having sex with your boyfriend, it might be helpful to talk to him about how it’s impacting your well-being and sex life.