Bacterial vaginosis (BV) is a common condition that affects many women, yet it often remains misunderstood or misdiagnosed. If you've ever experienced unusual discharge or a fishy smell and wondered what might be causing it, you're not alone.

In this ultimate guide to BV, we'll break down everything you need to know — from its causes and symptoms to treatment options and prevention tips.

What is BV?

Bacterial vaginosis is a vaginal infection caused by the overgrowth of bad bacteria in your vaginal microbiome. 

A healthy vaginal microbiome is made up mostly of healthy bacteria such as lactobacilli, a lactic-acid-producing bacteria that fight pathogens and keep infections away. 

When lactobacilli dominance is disrupted, your vaginal pH can go up, allowing other types of bacteria to grow and cause an imbalance (known in medicine as dysbiosis). This causes symptoms like discomfort, itching, and unusual vaginal discharge. ‍

If you’re dealing with bacterial vaginosis, you’re far from alone. According to the Centers for Disease Control (CDC), bacterial vaginosis is the most common vaginal condition in women ages 15-44. and almost 30% of people with vaginas get bacterial vaginosis each year.

BV symptoms 

The most common symptoms of bacterial vaginosis are watery, gray vaginal discharge and a strong fish-like odor.

Pain, discomfort, or vaginal itching, both in general or specifically with sex or peeing, can also be symptoms of BV. However, up to 84% of people with bacterial vaginosis may not experience anything at all.

Bacterial Vaginosis (BV) Symptoms infographic: fishy odor, gray discharge

What causes BV?

‍Bacterial vaginosis happens when the natural balance of your vaginal microbiome is thrown out of whack and anaerobic bacteria take over.

Research shows that certain activities or events may increase or decrease your risk of BV. Some of these risk factors include:

However, researchers still aren't sure what the exact cause of BV is, or how some women get it.

If you’re shocked that this is the best available answer for a condition that affects one in three women, you’re not alone. This is why Evvy exists! The vaginal microbiome and bacterial vaginosis are massively understudied, and it’s time women and people with vaginas got the research and care they deserve. ‍‍

The connection between BV and sex

Bacterial vaginosis is not a sexually transmitted infection (STI) and you can develop it without ever having sex. Because bacterial vaginosis is broadly defined as an imbalance in your vaginal microbiome, you can’t “get” bacterial vaginosis from having sex with someone. That said, sex itself (or really putting anything in your vagina) can introduce new bacteria and/or change the vaginal pH, allowing opportunistic bacteria to overgrow and cause bacterial vaginosis.  

Semen, saliva, or another vaginal microbiome can all disrupt your vaginal flora. This means that having unprotected sex or sex with a new partner can make you more likely to develop bacterial vaginosis.

Recurrent symptoms? Meet Evvy's at-home vaginal microbiome test, approved by leading OB-GYNs.
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Hormones and BV 

Hormones play a role in the composition of the vaginal microbiome. Estrogen, in particular, is an important variable in the health of your lactobacilli, the bacteria that create a lactic acid-dominant environment in the vagina. Anything that changes estrogen levels can affect the vaginal microbiome. 

This means that it’s important to pay extra attention to your vaginal microbiome anytime your hormones fluctuate, starting with:

What happens if BV is left untreated?

The bacteria present in your vaginal microbiome influence the risk of a variety of other health issues, and untreated BV increases your risk of serious complications, including: 

What is the difference between BV and a yeast infection? ‍

Bacterial vaginosis is not the same thing as having a yeast infection, which is caused by candida (yeast). The main underlying difference is that yeast infections are caused by an overgrowth of Candida (a type of fungus), while bacterial vaginosis is caused by an overgrowth of a variety of bacteria like Gardnerella

Though the symptoms in these two vaginal infections may overlap, yeast infections are typically characterized by a specific type of vaginal discharge (often compared to cottage cheese) and itchiness, while bacterial vaginosis is mostly associated with a fishy odor and thin white or gray vaginal discharge.‍

How is BV diagnosed? ‍

The world of vaginal diagnostics is complicated, but there are two traditional ways to diagnose bacterial vaginosis. The first is symptomatically, based on something called the Amsel criteria. An Amsel criteria diagnosis is when you have three of the four following symptoms:

  • white discharge
  • clue cells
  • a pH over 4.5
  • a fishy odor. 

A slightly more specific way to diagnose BV is with a Nugent score. Using the Nugent score, a vaginal smear is examined under a microscope for three bacteria morphotypes: Lactobacillus, Gardnerella, and curved gram rods.  

A score is then created based on how many of each type have been counted, essentially looking for low, intermediate, or high diversity of bacteria in the sample. A score under four is diagnosed as healthy, 4-7 is intermediate, and 7-10 is considered high diversity, aka, BV.  

You may have noticed that “high diversity” isn’t a very specific diagnosis — and you’re right. Unfortunately, current diagnostic measures don’t tell you much about what other bacteria are present or any other relevant information about how they’re interacting in your vaginal microbiome. 

This is why we’ve created an at-home vaginal microbiome test, so you can understand all the bacteria present in your microbiome. Though it’s not a diagnostic test and shouldn’t replace your doctor's advice, it can help you uncover what strains are present and in what capacity to understand how they may contribute to any symptoms.

How to treat BV 

You can treat bacterial vaginosis with antibiotics prescribed by a doctor. Commonly used antibiotics include clindamycin and metronidazole, as well as alternatives such as tinidazole or secnidazole.

Unfortunately, these are not great solutions for treating bacterial vaginosis for good — while antibiotics clear up to 85% of bacterial vaginosis cases within a month, for over half of these patients, the infection will return within six months. Some studies show recurrence rates as high as 80%, three months after “effective treatment.” Doesn’t sound so effective to us! 

It’s important to note that each antibiotic works better on some strains of bacteria compared to others, and certain ones spare the protective bacteria while others do not. When battling recurrent infections, knowing what specific bacteria are in your microbiome may be useful data for selecting an antibiotic. 

We hope that further research into the vaginal microbiome can create an opportunity for more precise and effective treatments in the future. ‍In the meantime, our Evvy Experts can help provide insights based on your microbiome to share with your medical provider.

‍Why does my BV keep coming back?

Recurrent bacterial vaginosis is pretty common because it tends to resist treatment or come back after successfully treating it. 

One potential reason why your BV is being stubborn is that a biofilm has formed in your vaginal microbiome. Bacteria are always trying to survive (who isn't) and sometimes they form what's called a biofilm. Biofilms are bacteria-made structures that protect the bacteria living inside them. Unfortunately, bacteria in a biofilm are harder to kill, making treatments like antibiotics less effective. This could be why BV has a high recurrence rate, but we're still learning about the exact role that biofilm plays in BV. 

One way to help prevent a BV recurrence is to take a probiotic with helpful strains of vaginal bacteria regularly. This ensures that protective bacteria are always being introduced to strengthen your natural defense against pathogens — even if you’re taking antibiotics.

Aside from medication, there are some everyday behaviors you can do to prevent bacterial vaginosis from coming back: 

  • Avoid douching and feminine hygiene products (like scented soaps or vaginal deodorants). Douching upsets the normal balance of bacteria in your vagina.
  • Wipe front to back after going to the toilet.
  • Change your period products within the proper time frame.
  • Choose underwear that is loose-fitting, lightweight, breathable, and made from a natural fabric, and change it often.
  • Practice safe sex and use condoms or dental dams (yes, even during oral sex).
  • Cover sex toys with a condom during partnered sex, and wash them with unscented soap/water after each use.
  • Quit smoking.


What causes you to have BV?

BV happens when the balance of bacteria in the vagina is off, allowing bad bacteria to outnumber the helpful ones. This can be caused by a few things, like having new or multiple sexual partners, douching, hormonal changes (during your period, pregnancy, or menopause), using intrauterine devices (IUDs), taking antibiotics, using scented vaginal products, and smoking. These factors mess with the natural bacteria in the vagina and increase the chance of getting BV. Knowing about and avoiding these triggers can help you maintain a healthy balance and avoid BV.

Is BV a form of STD?

No, bacterial vaginosis isn't considered a sexually transmitted disease (STD). While BV can be associated with sexual activity, such as having a new partner or multiple partners, it can also happen in women who aren't sexually active. BV is due to an imbalance in the vaginal flora, which can be influenced by various factors like douching, hormonal changes, and the use of certain vaginal products, rather than being directly transmitted through sexual contact. However, sexual activity can affect the balance of bacteria in the vagina and increase the risk of developing BV.

Can you get BV without having sex?

Yes, you can get bacterial vaginosis even if you're not sexually active — that’s why BV isn’t considered an STI. Although sex can be a trigger, for BV, it’s not the only one. Your period, smoking cigarettes, and using douches can all increase your risk of developing bacterial vaginosis. 

Will BV go away on its own? 

Sometimes, bacterial vaginosis can go away on its own. It often doesn’t cause symptoms so your immune system might get rid of it before you even notice. However, it’s best to see your healthcare provider if you’re experiencing bacterial vaginosis symptoms. Untreated BV is linked to a higher risk of contracting sexually transmitted infections, developing pelvic inflammatory disease, and even infertility. 

Is BV a yeast infection?

No, bacterial vaginosis and yeast infections aren't the same. BV happens when there's a balance issue in vaginal bacteria, causing a fishy odor and thin, gray discharge, while yeast infections are due to an overgrowth of Candida fungus, resulting in thick, white discharge, itching, and burning. BV is commonly treated with antibiotics, while antifungal medications usually treat yeast infections. Knowing the differences between these conditions is important for the right diagnosis and treatment.

Can men get BV?‍

Only people with vaginas can develop BV because by definition it is an imbalance in the vaginal microbiome. However, male genitalia can harbor pathogens that disrupt the vaginal microbiome.