Bacterial Vaginosis: Causes, Symptoms & Prevention

Have you noticed an unusual vaginal odor or a change in your discharge? One possible cause is bacterial vaginosis (BV), a common condition that develops when the natural balance of bacteria in the vagina changes.

Bacterial vaginosis is not caused by poor hygiene. It often causes thin, white or gray discharge and a noticeable fishy odor, particularly after sex. However, many women with BV experience no symptoms at all.

BV is also frequently confused with a vaginal yeast infection, even though the two conditions have different causes and require different treatments. Understanding the difference can help you avoid unnecessary products and know when medical care is appropriate.

Key Takeaways

BV develops when the normal balance of vaginal bacteria changes.
Common symptoms include thin vaginal discharge and a fishy odor.
Many women have BV without noticeable symptoms.
BV is different from a yeast infection and is treated with different medications.
Prescription antibiotics are the standard treatment for symptomatic BV.
BV can return after treatment, and recurrent cases may need additional management.
Probiotics are not established substitutes for medical treatment.

What Is Bacterial Vaginosis?

The vagina naturally contains a community of microorganisms known as the vaginal microbiome.

In many women, bacteria belonging to the Lactobacillus group help maintain a healthy vaginal environment by producing lactic acid. This keeps vaginal pH relatively acidic, usually below 4.5 during the reproductive years.

That acidity helps limit the growth of certain other microorganisms.

Bacterial vaginosis occurs when some protective Lactobacillus species decrease and other bacteria, including Gardnerella and several anaerobic species, become more abundant.

In simple terms, the problem is not that bacteria are present in the vagina. Bacteria belong there naturally. The problem is a change in their usual balance.

This is why BV is considered a type of vaginal dysbiosis, or microbial imbalance, rather than a problem that can be corrected by excessive washing.

Understanding the vaginal microbiome and common vaginal health concerns helps explain why a healthy vagina does not need internal cleansing products.

What Causes Bacterial Vaginosis?

Researchers have not identified a single cause responsible for every case of BV.

However, several factors have been associated with an increased likelihood of developing the condition.

Vaginal douching: Washing inside the vagina can disturb its natural bacterial environment.
Sexual activity: BV is associated with new or multiple sexual partners and inconsistent condom use.
Menstruation: BV may become more common around menstruation as the vaginal environment changes.
Copper intrauterine devices: Some studies have found an association with increased BV occurrence, although this does not affect every user.

Smoking has also been associated with BV in observational research, although the evidence does not establish that smoking directly causes every case.

Importantly, BV can occur in women who are not sexually active. It is not acquired from toilet seats, swimming pools, or bedding.

What Are the Symptoms of Bacterial Vaginosis?

Many women with BV do not notice anything unusual.

When symptoms occur, they commonly include:

Thin, white or gray vaginal discharge.
A distinctive fishy vaginal odor.
Odor that becomes more noticeable after sex or during menstruation.
Occasional mild irritation or itching.

Vaginal discharge itself is normal. Its amount and consistency can change throughout the menstrual cycle.

However, a new strong odor or persistent change in discharge may indicate BV or another condition that needs evaluation.

Severe itching, significant pain, or unusual bleeding are not typical features of uncomplicated BV and deserve medical attention.

How Is BV Different From a Yeast Infection?

Although both conditions affect the vaginal area, bacterial vaginosis and vaginal yeast infections have different causes.

Feature	Bacterial Vaginosis	Yeast Infection
Cause	Imbalance of vaginal bacteria	Overgrowth of Candida yeast
Discharge	Usually thin, white or gray	Often thick, white, and clumpy
Odor	Fishy odor is common	Strong odor is less typical
Itching	Often absent or mild	Frequently more pronounced
Treatment	Appropriate antibiotics	Antifungal medications

These are typical differences, not absolute diagnostic rules. Symptoms may overlap, and more than one condition can sometimes be present.

Burning during urination can also occur with urinary tract infections or irritation of the external genital tissues. The location and accompanying symptoms help guide assessment, but testing may still be necessary.

Using an over-the-counter antifungal treatment for every episode of abnormal discharge is not recommended. Antifungals do not treat BV and may delay appropriate care.

How Is Bacterial Vaginosis Diagnosed?

A healthcare professional usually begins by reviewing symptoms and may examine the vaginal discharge or collect a sample for testing.

Diagnostic methods include:

Vaginal pH measurement: BV is often associated with a pH above 4.5, although pH alone cannot confirm the diagnosis.
Microscopic examination: A sample may be examined for characteristic changes in vaginal cells and bacteria.
Laboratory testing: Gram staining or molecular tests may help identify BV in symptomatic patients.

Depending on symptoms and sexual health history, a clinician may also recommend tests for sexually transmitted infections or other causes of vaginal discharge.

Home vaginal pH strips cannot reliably distinguish BV from every other cause of abnormal discharge.

What Is the Best Treatment for Bacterial Vaginosis?

Prescription antibiotics are the standard treatment for symptomatic bacterial vaginosis.

Common options include:

Metronidazole: Available in oral tablets or vaginal gel formulations.
Clindamycin: Available as a vaginal cream or oral treatment in certain circumstances.

The appropriate medicine, formulation, and treatment duration depend on medical history, pregnancy status, allergies, and previous treatment response.

Symptoms may begin improving during the first few days, but it is important to follow the prescribed course even if discharge or odor improves sooner.

During treatment, clinicians generally advise avoiding sex or using condoms correctly and consistently.

Some oil-based vaginal clindamycin products can weaken latex condoms or diaphragms for several days, so product-specific instructions are important.

Why Does Bacterial Vaginosis Keep Coming Back?

BV recurrence is common, even after an effective initial treatment.

One possible explanation is that bacteria associated with BV can persist or the vaginal microbiome does not fully return to its previous state.

Sexual exchange of BV-associated bacteria may also contribute to recurrence in some people.

If symptoms return, it is better to confirm the diagnosis rather than repeatedly taking leftover antibiotics.

For multiple recurrences, a clinician may consider a different regimen or longer-term suppressive vaginal therapy.

Should Your Sexual Partner Be Treated?

This is an area where medical recommendations have changed.

In 2025, a randomized clinical trial found that treating male partners alongside women with BV, using a specific combination of oral and topical antibiotics, reduced recurrence during the study's follow-up period.

Following this evidence, the American College of Obstetricians and Gynecologists (ACOG) issued updated guidance in October 2025 supporting consideration of concurrent partner treatment in selected cases of recurrent, symptomatic BV.

However, this does not mean every partner automatically needs antibiotics.

The decision should be made with a healthcare professional, considering the individual situation and the available evidence.

Importantly, recurrent BV should not be interpreted as proof of infidelity or a conventional sexually transmitted infection.

How Can You Reduce the Risk of Bacterial Vaginosis?

There is no guaranteed method of preventing BV, but some habits may reduce recognized risk factors or help avoid vaginal irritation.

Avoid douching: The vagina cleans itself naturally, and internal washing can disturb its microbiome.
Choose gentle hygiene: Clean the external genital area with water and, if needed, a mild fragrance-free product.
Avoid scented vaginal products: Sprays, perfumed wipes, and internal deodorizing products may cause irritation.
Discuss condom use: Consistent condom use may reduce risk factors associated with sexual activity.
Avoid smoking: Smoking has established health risks and has also been associated with changes in the vaginal microbiome.

Comfortable underwear and changing out of wet clothing may help reduce irritation, but there is insufficient evidence that cotton underwear alone prevents BV.

Can Probiotics Treat or Prevent Bacterial Vaginosis?

Probiotics are live microorganisms that may provide specific health benefits when used in appropriate formulations and amounts.

Because Lactobacillus bacteria play an important role in the vaginal environment, researchers have investigated whether particular probiotic strains could help restore the vaginal microbiome after antibiotic treatment.

Some carefully studied vaginal Lactobacillus products have shown promising results in reducing BV recurrence.

However, those findings cannot automatically be applied to all commercially available oral or vaginal probiotic supplements.

Different products contain different species, strains, and amounts of microorganisms, so their effects are not interchangeable.

When considering a supplement, checking the ingredient names and amounts on supplement labels is important, although accurate labeling alone does not establish that a product treats BV.

Commercial probiotic supplements are not established replacements for antibiotic treatment. Inserting yogurt, oral probiotic capsules, or homemade mixtures into the vagina is also not a recommended treatment.

Is Bacterial Vaginosis Dangerous During Pregnancy?

Pregnant women experiencing unusual discharge, odor, or irritation should speak with their healthcare professional.

Symptomatic BV during pregnancy has been associated with an increased risk of complications, including preterm birth and premature rupture of membranes.

However, this does not mean every pregnant woman with BV will experience a complication.

CDC guidance recommends treating symptomatic BV during pregnancy with an appropriate medication selected by a clinician.

Routine screening of all pregnant women without symptoms solely to prevent preterm birth is not generally recommended.

When Should You See a Healthcare Professional?

Arrange an assessment if you experience:

A persistent new vaginal odor or unusual discharge.
Symptoms that could indicate BV, a yeast infection, or an STI.
Symptoms that return after treatment.
Unusual vaginal symptoms during pregnancy.
Pelvic pain, fever, or unexpected bleeding, which may indicate another condition requiring prompt evaluation.

Avoid putting vinegar, garlic, essential oils, or yogurt inside the vagina to treat odor or discharge. These remedies are not proven treatments and may cause irritation or delay appropriate care.

The Bottom Line

Bacterial vaginosis is a common change in the vaginal microbiome that may cause thin discharge and a distinctive odor, although many women have no symptoms.

For symptomatic BV, prescription antibiotics remain the standard treatment. When symptoms recur, confirming the diagnosis and discussing additional treatment options, including partner treatment in selected cases, can be helpful.

Most importantly, BV is not a sign of poor personal hygiene. Healthy vaginal care is about protecting the body's natural balance rather than using more cleansing products.

Frequently Asked Questions About Bacterial Vaginosis

Is bacterial vaginosis a sexually transmitted infection?

BV is not traditionally classified as a sexually transmitted infection, but sexual activity and the exchange of bacteria between partners can influence its development. BV can also occur without sexual activity.

How can I tell the difference between BV and a yeast infection?

BV commonly causes thin discharge with a fishy odor. Yeast infections more often cause pronounced itching and thick, white discharge. Symptoms can overlap, so testing may be needed.

Is bacterial vaginosis dangerous during pregnancy?

Symptomatic BV during pregnancy is associated with an increased risk of complications, including preterm birth. Pregnant women with unusual discharge or odor should seek medical assessment and appropriate treatment.

Can bacterial vaginosis come back after treatment?

Yes. BV can return even after successful antibiotic treatment. Recurring symptoms should be reassessed, and a clinician may recommend a different or longer-term treatment strategy.

Should my partner be treated for bacterial vaginosis?

For selected patients with recurrent, symptomatic BV, updated medical guidance supports considering treatment of an ongoing sexual partner. Partner treatment is not automatically necessary in every case.

Do probiotics cure bacterial vaginosis?

Commercial probiotic supplements are not established replacements for antibiotics. Research into specific vaginal Lactobacillus products is promising, but findings cannot be generalized to all probiotic supplements.

Does bacterial vaginosis need treatment if there are no symptoms?

Not every asymptomatic case requires treatment. The decision depends on medical circumstances, pregnancy, and planned procedures, and should be discussed with a healthcare professional.

Scientific References

Medical disclaimer: This article is intended for educational purposes and does not replace medical diagnosis or treatment. Speak with a healthcare professional about unusual vaginal symptoms, especially during pregnancy or when symptoms recur. Do not use prescription antibiotics or vaginal treatment products without appropriate guidance.

Bacterial Vaginosis: Causes, Symptoms, and Evidence-Based Prevention