Bacterial vaginosis is a common vaginal condition that occurs when the natural balance of bacteria in the vagina is disrupted, affecting millions of women worldwide. While many people experience no symptoms at all, others may notice unusual discharge with a distinctive odor that can cause significant discomfort and concern.

How Common Is Bacterial Vaginosis?

Bacterial vaginosis stands out as the most common cause of vaginal symptoms among women of reproductive age. According to global health data, approximately 23 to 29 percent of women worldwide are affected by this condition^[5]. In the United States specifically, bacterial vaginosis is the most prevalent vaginal problem for women between the ages of 15 and 44, with about 35 percent of people with a vagina experiencing it at some point^[1].

The condition affects different populations in varying ways. Research shows that Black women experience higher rates of bacterial vaginosis compared to white women, though scientists are still working to understand the exact reasons for this difference^[1]. The condition occurs globally but appears more frequently in areas with limited access to healthcare and in low-resource settings^[5].

While bacterial vaginosis is most common during the reproductive years, it can also affect postmenopausal women. Studies indicate that about 17 percent of postmenopausal women worldwide have bacterial vaginosis^[23]. The condition usually occurs in people who are sexually active, and it’s quite rare for it to develop in people who have never had sex^[1].

What Causes Bacterial Vaginosis?

A healthy vagina naturally contains many types of bacteria that normally balance each other out. This complex community of microorganisms is called the vaginal microbiome, which is the collection of all the bacteria living in the vagina. Bacterial vaginosis develops when this delicate balance is thrown off^[1].

Specifically, the condition happens when “good” bacteria, particularly a type called lactobacilli, which are beneficial bacteria that help maintain a healthy vaginal environment, decline in number. At the same time, “bad” bacteria, known as anaerobes, which are bacteria that can grow without oxygen, begin to multiply too quickly^[1]. This imbalance leads to an overgrowth of harmful bacteria such as Gardnerella species, Prevotella species, Mobilincus species, and other types that are not normally dominant^[5].

The exact trigger that causes this bacterial imbalance remains unclear to researchers. However, scientists know that anything that changes the natural chemistry of the vagina can affect its bacterial population. The vagina normally maintains an acidic environment, which helps keep harmful bacteria under control. When this acidity changes, problems can arise^[1].

It’s important to understand that bacterial vaginosis is not classified as a sexually transmitted infection. You cannot catch it from toilet seats, swimming pools, hot tubs, or by touching surfaces that someone with bacterial vaginosis has touched^[1]. However, the condition is linked to sexual activity in ways that scientists are still trying to fully understand^[2].

Risk Factors for Developing Bacterial Vaginosis

Several behaviors and situations can increase your chances of developing bacterial vaginosis. Understanding these risk factors can help you make informed choices about your health, though it’s crucial to know that having bacterial vaginosis is not something you did wrong^[19].

Sexual activity appears to be one of the strongest connections to bacterial vaginosis. Having a new sex partner, multiple sex partners, or resuming sexual activity after a long period of abstinence can introduce unfamiliar bacteria into the vagina^[19]. Women who have female sex partners may be at particular risk, as the condition can potentially spread between female partners^[17]. Not using barrier methods such as condoms consistently during sex also increases the likelihood of developing bacterial vaginosis^[8].

Pregnancy increases the risk of developing bacterial vaginosis, likely due to hormonal changes that occur during this time^[1]. Women who have an intrauterine device, or IUD, which is a small device inserted into the uterus for birth control, may also have a higher risk. Interestingly, certain copper-containing IUDs have been associated with increased bacterial vaginosis rates^[10].

Taking antibiotics for other infections can sometimes trigger bacterial vaginosis because these medications can kill both harmful and beneficial bacteria in the vagina^[1]. Using perfumed products in or around the vagina, including scented soaps, vaginal deodorants, bubble baths, and douches, can also upset the natural balance^[3].

Lifestyle factors play a role as well. Smoking has been associated with an increased risk of bacterial vaginosis^[8]. Additionally, practices like inserting herbs or other products into the vagina can increase risk^[5].

Some women may naturally produce too much of the bacteria that causes bacterial vaginosis, making them more susceptible to the condition^[1]. Male circumcision has been shown to reduce the risk for bacterial vaginosis among female partners, though the reasons for this protective effect are still being studied^[10].

Recognizing the Symptoms of Bacterial Vaginosis

One of the most challenging aspects of bacterial vaginosis is that many people who have it don’t experience any symptoms at all. In fact, up to 84 percent of people with bacterial vaginosis have no symptoms whatsoever^[1]. This means you could have the condition without realizing it, which is why regular checkups with a healthcare provider are so important.

When symptoms do occur, the most distinctive sign is vaginal discharge that looks different from what’s normal for you. The discharge is typically thin and watery rather than thick, and it may appear off-white, gray, or even greenish in color^[1]. Some women describe the consistency as milklike, coating the vaginal walls smoothly^[10].

The hallmark symptom that sets bacterial vaginosis apart from other vaginal conditions is a strong “fishy” odor from the vaginal discharge. This smell often becomes more noticeable after sexual intercourse^[1]. The odor can be embarrassing and distressing for many women, but it’s important to remember that it’s simply a symptom of a bacterial imbalance that can be treated.

Some women experience vaginal itching or irritation, though this is less common with bacterial vaginosis compared to other vaginal infections like yeast infections^[1]. You might also notice a burning sensation when urinating^[2].

Symptoms can sometimes come and go, or they may be so mild that you barely notice them^[6]. The vaginal pH, which measures acidity, increases above 4.5 in bacterial vaginosis, though you wouldn’t be able to detect this change without medical testing^[10].

Because the symptoms of bacterial vaginosis are similar to other vaginal infections and sexually transmitted infections, it’s crucial to see a healthcare provider for an accurate diagnosis rather than trying to self-diagnose or self-treat^[1]. What you think might be bacterial vaginosis could actually be a yeast infection, trichomoniasis, or another condition requiring different treatment.

Preventing Bacterial Vaginosis

While healthcare providers and scientists don’t completely understand how to prevent bacterial vaginosis with certainty, there are several steps you can take to reduce your risk. The best prevention strategy is maintaining regular checkups with your gynecologist, even when you feel fine^[19].

Using condoms correctly every time you have sex may help lower your risk of developing bacterial vaginosis^[17]. Limiting the number of sexual partners can also reduce risk^[17]. Some research suggests that hormonal contraception, such as birth control pills, might actually provide some protection against bacterial vaginosis^[10].

One of the most important prevention measures is avoiding douching entirely. Healthcare providers universally recommend against this practice because it disrupts the natural bacterial balance in the vagina^[17]. Similarly, you should avoid using vaginal deodorants, perfumed soaps, bubble baths, or scented products in the bath^[3]. Don’t put antiseptic liquids in your bathwater, as these can also disturb the vaginal environment^[3].

For daily hygiene, use only plain water or a mild, unscented soap to wash the outside genital area. There’s no need to clean inside the vagina, as it has a self-cleaning mechanism^[3]. Taking showers instead of baths may also help^[3]. Avoid using strong detergents to wash your underwear^[3].

Wearing loose cotton clothing that doesn’t trap heat and moisture close to the skin can help maintain a healthy vaginal environment^[18]. If you smoke, quitting can reduce your risk of bacterial vaginosis along with providing many other health benefits^[3].

While these measures may help reduce your risk, it’s important to understand that even when following all prevention guidelines, bacterial vaginosis can still occur. If it does develop, it’s not a reflection of poor hygiene or anything you did wrong^[19].

How Bacterial Vaginosis Changes Normal Body Function

To understand what happens in bacterial vaginosis, it helps to know how the vagina normally functions. A healthy vagina maintains a carefully controlled environment where beneficial bacteria, especially lactobacilli, dominate the microbial community. These good bacteria produce hydrogen peroxide and lactic acid, which keep the vaginal pH acidic, typically between 3.8 and 4.5^[4].

This acidic environment serves as a natural defense system. It prevents harmful bacteria from growing out of control and protects against infections. The lactobacilli essentially act as guardians, maintaining conditions that are favorable for vaginal health but unfavorable for potential pathogens.

In bacterial vaginosis, the number of hydrogen peroxide-producing lactobacilli decreases significantly^[4]. Without enough of these protective bacteria, the vaginal pH rises above 4.5, making the environment less acidic^[20]. This change in acidity allows anaerobic bacteria to flourish.

As harmful bacteria like Gardnerella vaginalis, Atopobium vaginae, and others multiply, they replace the beneficial lactobacilli. These bacteria produce substances that create the characteristic fishy odor and thin discharge associated with bacterial vaginosis^[20]. A distinctive feature of bacterial vaginosis is the formation of a biofilm, which is a layer of bacteria that sticks to the vaginal walls like a protective coating, making the infection harder to clear^[10].

Under a microscope, cells from the vaginal walls in bacterial vaginosis show a telltale sign: they become covered with bacteria, creating what are called “clue cells.” These cells get their name because they provide an important clue to diagnosing the condition^[19].

The changes in the vaginal environment don’t just cause symptoms—they also affect the body’s natural defenses. The less acidic environment and reduced number of protective bacteria make the vagina more vulnerable to infections. This helps explain why bacterial vaginosis increases the risk of acquiring sexually transmitted infections, including HIV^[5].

When left untreated, bacterial vaginosis can lead to more serious health problems. The bacteria can sometimes spread from the vagina to the uterus, ovaries, or fallopian tubes, causing pelvic inflammatory disease, which is an infection of the female reproductive organs that can lead to chronic pain and fertility problems^[19]. The condition also increases vulnerability to other sexually transmitted infections and can affect transmission of HIV to partners^[10].

Interestingly, bacterial vaginosis can sometimes resolve on its own without treatment. The condition is described as “self-limiting,” meaning the body may eventually restore the bacterial balance naturally^[8]. However, this doesn’t always happen, and waiting for spontaneous resolution carries the risk of complications, especially during pregnancy.