How Does Sex Between Two People With Vaginas Affect the Vaginal Microbiome?

Sex is one of the most common triggers for vaginal symptoms and infections. But thanks to centuries-long bias towards heterosexuality, the little research that has been done on sex and the vaginal microbiome has predominantly addressed sex between male and female couples. 

We firmly believe everyone deserves equal research and easily accessible health resources, so we’ve created a round-up of the research that does exist for people with vulvas having sex with other vulva-owners. Read on to learn more!  

How does sex between people with vaginas affect the vaginal microbiome? 

Sex between people with vaginas can include skin-to-skin contact between vulvas, oral sex, sharing sex toys, fingering, and more — all of which can affect the vaginal microbiome! 

Why? The short answer is just about anything in or around your vagina or vulva can shift the balance of your vaginal microbiome by introducing new bacteria and fungi.

Fingers, mouths, and other body parts all have their own microbiomes — and might be home to pathogenic microbes. When disruptive microbes are introduced to your vagina during sex, there is a chance they will overgrow and disrupt the composition of your vaginal microbiome, and in some cases, catalyze unwanted infections like BV or yeast infections. 

Vulva to vulva contact 

Have you ever heard of a vaginal microbiome transplant (VMT)? It’s a relatively new procedure that may help treat bacterial vaginosis (BV) by putting the vaginal microbiome of a healthy person into the vagina of a patient with BV. 

Every time a vulva comes in direct contact with another vulva, it essentially facilitates a naturally occurring vaginal microbiome transplant (which is pretty cool if you ask us!) 

Even better, science backs this theory up: people with vaginas whose partners’ microbiomes are “healthy” (low diversity and lactobacilli dominant) are more likely to have a stable microbiome and less likely to develop BV. 

However, it has been documented time and again that people with vaginas in same-sex relationships have a higher rate of BV with the incidence ranging from 25-52% of the population. 

A 2019 study tracked the vaginal microbiomes of 102 women who were negative for BV and having sex with other women. Researchers found that sex with a new partner (as opposed to ongoing sex with a current partner) was associated with increased bacterial diversity (which is often a marker of BV). 

Other behaviors associated with BV included: sex several times a week, multiple partners in a month, previous history of BV, smoking, receiving digital anal sex, and receiving oral sex.  

This data suggests that vaginal microbiomes shift and adapt with those of your partner. If both people have stable Lactobacillus dominant microbiomes, then they will most likely stay that way. But any big shift in one partner will probably affect the other partner as well. 

Whether you’re having sex with a new partner, multiple partners, or a long-term partner, it’s a good idea to test your vaginal microbiome (ideally over time!) to see which types and quantities of bacteria and fungi are residing in your vagina, especially if you’re having symptoms, so you don’t accidentally disrupt your partner’s microbiome during sex! 

Genital stimulation or fingering

The good news is, there are endless ways to stimulate a partner with your hands. The bad news is that hands—particularly fingernail beds—carry a lot of germs. 

Just think about it. We touch hundreds, if not thousands of surfaces every day. And if not washed properly before sex (we’re talking soap, people!), the bacteria on your partner’s hands can disrupt your vaginal microbiome.

Oral sex and sex toys   

Not only does oral sex feel good for many people, but the lubrication it provides can help combat vaginal dryness that can make sex painful! But, alas, like any other sexual activity, unprotected oral sex poses some risk to your vaginal microbiome. 

The mouth is home to literally billions of bacteria and fungi. In fact, after the gut, the oral microbiome is the second-largest and most diverse microbiota in your body! So, naturally, oral sex may enable microbes from a partner’s mouth to make their way into your vaginal microbiome.

In a 2019 study, 85% of queer women reported receiving oral sex from their partner. Another 72% reported using sex toys with their partner. Findings showed that those who engaged in oral sex and used sex toys were more likely to have a vaginal microbiome with disruptive bacteria.

Like penetrative sex, these sexual practices are also considered to be a risk factor for bacterial vaginosis. 

How to keep your vaginal microbiome healthy

• Practice safe sex. Use a barrier method like condoms (even with toys if you're prone to infections!) and dental dams.
• Care for your toys. Wash and dry your sex toys before and after each use.
• Don’t cross-contaminate! After anal play, make sure to change your condom or wash your sex toy before vaginal penetration.
• Proactive testing — including STI testing. When it comes to caring for your sexual health, it’s important to get tested for STIs so as not to put you or your partner at risk! Evvy's at-home Vaginal Microbiome + STD Test can show you exactly what’s up down there. Remember, up to 84% of people with bacterial vaginosis don’t show any symptoms, but BV can put you at higher risk for STI acquisition, vaginal infections, preterm birth, and more.
• Pee (or shower) after sex to help clear the urethra of pathogens. Admittedly, the jury’s out on whether this actually prevents infections, but it can’t hurt!  
• Choose condoms and lube wisely. Avoid spermicides, fragrances, nitrosamines, benzocaines, parabens, and glycerin, all of which may impact the vaginal microbiome.
• Consider partner treatment. Given that partners may harbor the bacteria that can cause symptoms and lead to infection, it may be worthwhile for both parties to be treated. Talk to your doctor regarding if this may be a useful approach for you.
• Changing your period products within the proper time frame