What Is Bacterial Vaginosis?

Facts Every Woman Should Know

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Bacterial vaginosis (BV) is a common but frustrating condition in which the balance of bacteria in the vagina gets out of sync. Usually, the body is able to maintain the ideal balance. But if the balance is disrupted, certain types of bacteria can overgrow and cause symptoms.

BV is readily treated and usually doesn't cause any other health problems. With that said, it can increase the risk of getting a sexually transmitted disease (STD) or lead to birth complications in people who are pregnant.

Bacterial vaginosis symptoms
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This article looks at the symptoms, causes, and risk factors of bacterial vaginosis. It also explains how BV is diagnosed, treated, and prevented.

Bacterial Vaginosis Symptoms

Of the 21 million women in the United States believed to have bacterial vaginosis each year, only around three million actually have symptoms.

When they occur, the symptoms of BV tend to be mild but persistent and may include:

  • A grayish-white or yellow vaginal discharge
  • A "fishy" smell that can get worse after intercourse
  • A burning sensation when urinating
  • Vaginal itchiness, redness, and swelling
  • Vaginal bleeding after intercourse

While BV symptoms are rarely serious, they can weaken vaginal tissues and increase the risk of STDs such as gonorrheachlamydiatrichomoniasis, and HIV.

If an infection occurs during pregnancy, there is an increased risk of preterm (premature) birth, low birth weight, and, in rare instances, miscarriage.


Symptoms of bacterial vaginosis include a vaginal discharge with a fishy smell. Itching, redness, swelling, burning with urination, and bleeding with intercourse are also common.


Bacterial vaginosis occurs when the level of "good" bacteria in the vagina suddenly drops. This allows "bad" bacteria to grow excessively. The main "good" bacteria, called lactobacillus, makes the vagina slightly acidic so that "bad" bacteria can't overgrow.

Sex can instigate BV by introducing new or excessive amounts of bacteria into the vagina.

Some of the more common causes of BV include:

  • Condomless sex
  • Multiple sex partners
  • New sex partners
  • Shared sex toys
  • Douching
  • Bubble baths
  • Vaginal deodorants
  • Smoking
  • Intrauterine devices (IUDs)

Genetics is also believed to play a part, either by promoting inflammation or by causing the inadequate production of lactobacillus.


Sex can lead to bacterial vaginosis by introducing new bacteria into the vagina, This is especially true if you don't use condoms or have multiple sex partners. Smoking, douching, and IUDs can also increase the risk.


Since bacterial vaginosis is not caused by a single agent, the diagnosis is largely based on a review of your medical history and symptoms along with various lab tests and procedures.

These include::

  • A pelvic exam
  • A pH test to check for vaginal acidity
  • A microscopic evaluation of vaginal fluids

The microscopic exam would look for "clue cells" (meaning vaginal cells studded with bacteria). Agram stain would also be used to differentiate "good" bacteria from "bad" ones, allowing the lab to check for imbalances in the vaginal flora.

Additional tests may be performed to rule out other possible causes, such as a yeast infection or genital herpes.


The diagnosis of bacterial vaginosis typically involves a review of symptoms and medical history, a pelvic exam, a vaginal pH test, and a microscopic evaluation of vaginal fluids.


The standard treatment for bacterial vaginosis is a short course of antibiotic drugs. Antibiotics are a class of drugs that specifically treat bacterial infections.

The first-line options are Flagyl (metronidazole) and clindamycin. Both are highly effective in treating BV and have relatively mild side effects.

The preferred first-line regimens include:

  • Metronidazole 500 milligrams (mg) taken by mouth twice daily for seven days
  • Metronidazole 0.75% vaginal gel applied once daily for five days
  • Clindamycin 2.0% vaginal cream applied at bedtime for seven days

Alternate treatments include a clindamycin vaginal suppository or Tindamax (tinidazole) tablets. Despite the effectiveness of these drugs, recurrence is common and may require multiple treatments to fully clear the infection.

Side effects include nausea, stomach ache, cough, sore throat, runny nose, and a metallic taste in the mouth.

In addition to antibiotics, several supportive remedies may help. These include probiotics (beneficial live bacteria found in yogurt and probiotic supplements) that may help prevent a recurrence. Boric acid (available as a capsule and vaginal suppository) is an old-time remedy attracting renewed medical interest.

During treatment, wear looser pants or skirts to reduce vaginal moisture and heat that can promote bacterial growth. You can also reduce itching and swelling by applying a cool cloth to the vagina or splashing it with cold water.


The first-line antibiotics used to treat bacterial vaginosis include oral metronidazole (a.k.a. Flagyl), topical metronidazole, and topical clindamycin.

Bacterial Vaginosis Doctor Discussion Guide

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As common as bacterial vaginosis is, there are things you can do to reduce your risk. These include safer sex practices and practicing good vaginal hygiene.

To prevent bacterial vaginosis:

  • Limit the number of sex partners.
  • Use condoms correctly and consistently.
  • Do not douche.
  • Avoid bubble baths and vaginal deodorants.
  • Wipe from front to back after urinating.
  • Avoid IUDs if you have recurrent BV or have had severe BV in the past.


You can reduce the risk of BV by practicing safer sex, avoiding douching, and wiping from front to back after peeing. You may be advised to avoid IUDs if you have recurrent BV.


Bacterial vaginosis (BV) is a common infection caused by an imbalance of the vaginal flora. When "good" bacteria like lactobacillus are abnormally low, "bad" bacteria can overgrow, causing vaginal redness, itching, swelling, and a fishy-smelling discharge.

Sex can lead to BV by introducing new bacteria into the body. Risk factors include condomless sex, multiple sex partners, smoking, douching, and IUDs.

The diagnosis of BV typically involves a pelvic exam, a vaginal pH test, and a microscopic evaluation of vaginal fluids. BV is treated with oral or topical antibiotics, most commonly metronidazole and clindamycin.

The risk of BV can be reduced by practicing safer sex, avoiding douching, and wiping from front to back after urination. People with recurrent or severe BV may be advised to avoid IUDs.

A Word From Verywell

Even with the best prevention efforts, bacterial vaginosis can occur. Try not to stress it does. Instead, seek treatment and make every effort to avoid worsening the condition.

If prescribed antibiotics, do not stop early even if the symptoms disappear. If you do, antibiotic resistance can occur, making the infection harder to treat if it returns.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  9. Homayouni A, Bastani P, Ziyadi S, et al. Effects of probiotics on the recurrence of bacterial vaginosis: a review. J Low Genit Tract Dis. 2014;18(1):79-86.

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Additional Reading
Elizabeth Boskey, PhD

By Elizabeth Boskey, PhD
Boskey has a doctorate in biophysics and master's degrees in public health and social work, with expertise in transgender and sexual health.