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Bacterial vaginosis is the most common type of vaginal infection. To learn more about other common types, see the topics Vaginal Yeast Infections and Trichomoniasis.

What is bacterial vaginosis?

Bacterial vaginosis is a mild infection of the vagina caused by bacteria. Normally, there are a lot of “good” bacteria and some “bad” bacteria in the vagina. The good types help control the growth of the bad types. In women with bacterial vaginosis, the balance is upset. There are not enough good bacteria and too many bad bacteria.

Bacterial vaginosis is usually a mild problem that may go away on its own in a few days. But it can lead to more serious problems. So it’s a good idea to see your doctor and get treatment.

What causes bacterial vaginosis?

Experts are not sure what causes the bacteria in the vagina to get out of balance. But certain things make it more likely to happen. Your risk of getting bacterial vaginosis is higher if you:

• Have more than one sex partner or have a new sex partner.
• Smoke.
• Douche.

You may be able to avoid bacterial vaginosis if you limit your number of sex partners and don't douche or smoke.

Bacterial vaginosis is more common in women who are sexually active. But it is probably not something you catch from another person.

What are the symptoms?

The most common symptom is a smelly vaginal discharge. It may look grayish white or yellow. A sure sign of bacterial vaginosis is a "fishy" smell, which may be worse after sex. About half of women who have bacterial vaginosis do not notice any symptoms.

Many things can cause abnormal vaginal discharge, including some sexually transmitted diseases (STDs). See your doctor so you can be tested and get the right treatment.

How is bacterial vaginosis diagnosed?

Doctors diagnose bacterial vaginosis by asking about the symptoms, doing a pelvic exam, and taking a sample of the vaginal discharge. The sample can be tested to find out if you have bacterial vaginosis.

What problems can bacterial vaginosis cause?

Bacterial vaginosis usually does not cause other health problems. But it can lead to serious problems in some cases.

• If you have it when you are pregnant, it increases the risk of miscarriage, early (preterm) delivery, and uterine infection after pregnancy.
• If you have it when you have a pelvic procedure such as a C-section, abortion, or hysterectomy, you are more likely to get a pelvic infection.
• If you have it and you are exposed to a sexually transmitted disease (including HIV), you are more likely to catch the disease.

Getting treated with antibiotics can help prevent these problems.

How is it treated?

Doctors usually prescribe an antibiotic to treat bacterial vaginosis. The ones used most often are metronidazole (such as Flagyl) and clindamycin (such as Cleocin). They come as pills you swallow or as a cream or capsules (called ovules) that you put in your vagina. If you are pregnant, you will need to take pills.

Bacterial vaginosis usually clears up in 2 or 3 days with antibiotics, but treatment goes on for 7 days. Do not stop using your medicine just because your symptoms are better. Be sure to take the full course of antibiotics.

If you are treated with antibiotics:

• Avoid all alcohol use, including over-the-counter medicines that contain alcohol (such as NyQuil), if you are taking metronidazole or tinidazole. Mixing alcohol and metronidazole, or alcohol and tinidazole, can cause severe nausea and vomiting.
• The oil in clindamycin cream and ovules can weaken latex. This means condoms and diaphragms may break, and you may not be protected from STDs or pregnancy.

Antibiotics usually work well and have few side effects. But taking them can lead to a vaginal yeast infection. A yeast infection can cause itching, redness, and a lumpy, white discharge. If you have these symptoms, talk to your doctor about what to do.

Frequently Asked Questions

Cause

Bacterial vaginosis is caused by an imbalance of the organisms (flora) that naturally exist in the vagina. Normally, about 95% of vaginal flora are lactobacillus bacteria. (These types are unique to humans, different from the lactobacillus in yogurt.) These lactobacilli help keep the vaginal pH level low and prevent overgrowth of other types of organisms. Women with bacterial vaginosis have fewer lactobacillus organisms than normal and more of other types of bacteria. Experts do not yet understand what causes this imbalance.

Although the specific cause isn't known, a number of health and lifestyle factors have been linked to bacterial vaginosis. For more information, see the What Increases Your Risk section of this topic.

Symptoms

About half of women with bacterial vaginosis have no symptoms.¹ Bacterial vaginosis does not typically cause itching. But it does cause:

• An excessive grayish white vaginal discharge, unlike normal vaginal discharge (1 out of 3 women who have bacterial vaginosis describe the discharge as yellow).²
• A bothersome "fishy" odor, which is usually worse after sex (intercourse).

Other conditions with similar symptoms include some sexually transmitted diseases (especially trichomoniasis), urinary tract infection, and vaginal yeast infection.

What Happens

Bacterial vaginosis often clears up on its own. But in some women it doesn't go away on its own. And for many women it comes back after it has cleared up. Antibiotic treatment works for some women but not others. Bacterial vaginosis recurs in about 1 out of 3 treated women.¹

Complications

Your risk of complications from bacterial vaginosis is higher:

• During pregnancy. Compared to pregnant women who don't have it, women who have bacterial vaginosis during pregnancy have a higher risk of early (preterm) delivery or of uterine infection after pregnancy. Also, pregnant women may have an increased risk of miscarriage.
• After gynecological surgery. Women with bacterial vaginosis at the time of an invasive vaginal procedure have an increased risk of developing more serious infection or inflammation, such as pelvic inflammatory disease (PID) or endometritis. Surgical procedures linked to bacterial vaginosis-related infection include endometrial biopsy, surgical abortion, hysterectomy, intrauterine device (IUD) placement, cesarean section, dilation and curettage (D&C), and an X-ray test that examines the inside of the uterus, the fallopian tubes, and surrounding area (hysterosalpingography).³
• When exposed to HIV or other sexually transmitted diseases. Women who have bacterial vaginosis when they are exposed to sexually transmitted diseases (including HIV) have an increased risk of becoming infected with the sexually transmitted disease.

What Increases Your Risk

Factors that increase your risk of getting bacterial vaginosis include:

• Having more than one sex partner or having a new sex partner.
• Smoking.
• Douching.

Although bacterial vaginosis can be triggered by or get worse from sexual activity, it does not appear to be an infection that is passed from man to woman. So experts do not consider bacterial vaginosis to be a male-female sexually transmitted disease. Bacterial vaginosis may be passed from woman to woman during sexual contact.

When To Call a Doctor

Bacterial vaginosis can be difficult to distinguish from other types of vaginal infection. Consider the following if you have any signs of vaginal infection.

Call your doctor immediately if you:

• Develop lower belly pain and a fever higher than 101°F (38.33°C) along with a vaginal discharge.
• Are pregnant and have symptoms of a vaginal infection.

Call your doctor for an appointment within 1 week if you:

• Have an unusual vaginal discharge that has a foul odor, especially noticeable after sex.
• Have unusual vaginal itching.
• Have pain during sex or during urination.
• Develop any other discomfort or discharge that may indicate a vaginal infection.

If you have not been diagnosed with bacterial vaginosis but you have symptoms that cause you concern, see the following topics:

• Female Genital Problems
• Abdominal Pain, Age 12 and Older
• Abnormal Vaginal Bleeding

Watchful Waiting

It's generally recommended that you contact or see your doctor about vaginal symptoms. The only exception to this rule is when you are sure that your vaginal symptoms mean that you have a vaginal yeast infection. If you have had a yeast infection before and are sure that your problem is a yeast infection rather than bacterial vaginosis, you can consider home treatment with a nonprescription product to treat yeast infections. For more information, see the topic Vaginal Yeast Infections.

If your symptoms are due to a sexually transmitted disease (STD) and not bacterial vaginosis, you may infect a sex partner if you delay treatment. You may also develop more serious complications of STDs such as pelvic inflammatory disease (PID).

• To prevent the spread of a possible infection, avoid sex. Wait until after you have seen your doctor.
• Avoid douching.

Who To See

Doctors who can diagnose and treat bacterial vaginosis include:

• Family medicine doctors.
• Gynecologists.
• Nurse practitioners.
• Internists.
• Physician assistants.

To prepare for your appointment, see the topic Making the Most of Your Appointment.

Exams and Tests

Your doctor may only test you for bacterial vaginosis if you:

• Have symptoms.
• Are going to have a hysterectomy or surgical abortion (bacterial vaginosis increases infection risk afterwards).
• Are pregnant and have had a preterm delivery in the past (a past preterm delivery may have been caused by infection).

Your doctor can diagnose bacterial vaginosis based on your history of symptoms, a vaginal exam, and a sample of the vaginal discharge. Laboratory tests to detect signs of bacterial vaginosis may include:

• Wet mount. A sample of vaginal discharge is mixed with a salt (normal saline) solution after placing it on a microscope slide. The prepared slide is examined to identify the bacteria present, to look for white blood cells that point to an infection, and to look for unusual cells called clue cells. The presence of clue cells is the most reliable sign of bacterial vaginosis.
• Whiff test. Several drops of a potassium hydroxide (KOH) solution are added to a sample of vaginal discharge to find out whether a strong fishy odor is produced. A fishy odor on the whiff test suggests bacterial vaginosis.
• Vaginal pH. The normal vaginal pH is 3.8 to 4.5. Bacterial vaginosis usually causes the vaginal pH to rise above 4.5.
• Gram stain. A sample of the vaginal discharge is placed on a microscope slide. A special dye is applied to the slide, causing certain types of bacteria (Gram-positive bacteria) to turn a shade of purple while coloring others (Gram-negative bacteria) pink. In bacterial vaginosis, Gram-negative bacteria, especially Gardnerella vaginalis, are most common.
• Oligonucleotide probes. This test detects the genetic material (DNA) of bacterial vaginosis bacteria. Oligonucleotide probe testing is very accurate but is not routinely available in most labs.

The presence of clue cells, an increased vaginal pH, and a positive whiff test are enough evidence to treat for bacterial vaginosis.

Bacterial vaginosis may be detected during routine Pap testing. But Pap testing is not a standard test to diagnose bacterial vaginosis.

Treatment Overview

Treatment options for bacterial vaginosis include:

• Watchful waiting. Bacterial vaginosis symptoms may go away on their own. This happens when the vaginal lactobacilli organisms increase to their normal levels, and other bacteria levels drop.
• Antibiotic medicine (oral or vaginal). Antibiotics can kill the problem bacteria causing bacterial vaginosis symptoms but sometimes don't reverse the cause. So symptoms recur in about 1 out of 3 of women after antibiotic treatment.¹

For some women, bacterial vaginosis goes away without treatment. But when it does not go away even with treatment, bacterial vaginosis is frustrating and troublesome. And it can lead to preterm labor if you have it during pregnancy. If present during pelvic surgery or invasive vaginal procedures, bacterial vaginosis makes the reproductive tract vulnerable to infection or inflammation, which has been linked to such problems as pelvic inflammatory disease (PID). So your doctor will test and treat you with antibiotics for bacterial vaginosis if you are:

• Having persistent symptoms.
• Pregnant and have symptoms.
• Pregnant with no symptoms, but have a history of preterm labor (before 37 completed weeks of pregnancy) that may have been related to infection.⁴
• Planning to have a hysterectomy or surgical abortion. Treating bacterial vaginosis with antibiotics beforehand greatly lowers your risk of getting a serious infection afterward. Other procedures linked to bacterial vaginosis-related infection include endometrial biopsy, intrauterine device (IUD) placement, cesarean section, dilation and curettage (D&C), and hysterosalpingography, an X-ray test that examines the inside of the uterus, the fallopian tubes, and surrounding area.³

Talk to your doctor about whether screening is right for you.

What To Think About

If you are planning to become pregnant and have symptoms or a history of bacterial vaginosis, talk to your doctor about screening and treatment before you start a pregnancy.

Women should not breast-feed while taking tinidazole or for 3 days after they are finished taking this medicine.

For decades, some women have used Lactobacillus acidophilus in yogurt or supplements to treat bacterial vaginosis. But experts now know that dairy lactobacillus is not the kind that normally lives in the vagina. This is why dairy lactobacillus does not work for bacterial vaginosis. But researchers have found that two different types of lactobacillus—L. crispatus and L. jensenii—are most commonly found in a healthy vaginal environment. Research is now focusing on using these types of lactobacilli in capsules.⁵

If your doctor finds other problems during the exam, such as a possible sexually transmitted disease (STD), appropriate treatment will be recommended.

Since it probably is not passed between a man and woman, treating a male sex partner or partners will not help cure bacterial vaginosis.³ But for a woman with a female sex partner, it is possible that bacterial vaginosis is passed back and forth, although this is not yet proved. In this case, treating both partners may help.

Prevention

To help prevent bacterial vaginosis:

• Limit the number of sex partners you have. Multiple sex partners increase your risk of getting bacterial vaginosis by changing the normal environment of the vagina.
• Avoid douching.

Bacterial vaginosis may be passed between women during sexual contact. If you have a female sexual partner, you may benefit from using condoms with or careful washing of shared sex items.⁶

Bacterial vaginosis is not passed between men and women and is not considered a sexually transmitted disease (STD). But if you are exposed to an STD while you have bacterial vaginosis, you are more likely to be infected by that disease.

It is always important to practice safe sex to prevent sexually transmitted diseases, whether or not you have bacterial vaginosis. Preventing an STD is easier than treating an infection after it occurs.

Home Treatment

For decades, some women have used Lactobacillus acidophilus in yogurt or supplements to treat bacterial vaginosis. But dairy lactobacillus does not work for bacterial vaginosis. This is because dairy lactobacillus is not the kind of bacteria that normally live in the vagina.⁶

Researchers are studying the two different types of lactobacillus—L. crispatus and L. jensenii—that are most commonly found in a healthy vagina.⁵ These lactobacilli may prove to be an effective treatment for bacterial vaginosis.

Medications

The antibiotics metronidazole (such as Flagyl and MetroGel), clindamycin (such as Cleocin and Clindesse), and tinidazole (such as Tindamax) are used to treat bacterial vaginosis. Depending on the antibiotic you are prescribed, you may take it by mouth or use it vaginally.

During pregnancy, women who are high-risk for preterm labor are advised to avoid vaginal application of any treatment. Some doctors recommend that all pregnant women avoid vaginal treatments.

Medicines inserted into the vagina cause fewer side effects than oral medicines, although they can make you vulnerable to vaginal yeast infection.

When considering treatment for bacterial vaginosis, ask your doctor whether you should:

• Use oral medicine or medicine inserted into the vagina. Some women prefer to take pills rather than using a vaginal medicine.
• Avoid having sex during the time that you are being treated.
• Continue treatment during your menstrual period. Medicine placed in your vagina is harder to use during your period, but your doctor may recommend continuing treatment during this time.
• Avoid drinking alcohol during treatment with metronidazole or tinidazole. These medicines can cause severe nausea and vomiting if you drink alcohol when you are taking one of them. Clindamycin does not.

The oil in clindamycin cream and ovules can weaken latex. This means condoms and diaphragms may break, and you may not be protected from STDs or pregnancy.

Surgery

There is no surgical treatment for bacterial vaginosis.

Other Treatment

For decades, some women have used Lactobacillus acidophilus in yogurt or supplements to treat bacterial vaginosis. But researchers now know that dairy lactobacillus does not work for bacterial vaginosis. This is because dairy lactobacillus is not the kind of bacteria that normally lives in the vagina. Researchers have found two different types of lactobacillus—L. crispatus and L. jensenii—that are most commonly found in a healthy vaginal environment. Research is now focusing on using these types of lactobacilli in capsules.⁵

Other Places To Get Help

Organizations

Related Information

• Abnormal Pap Test
• Exposure to Sexually Transmitted Diseases
• Pap Test
• Pelvic Inflammatory Disease
• Preterm Labor
• Trichomoniasis
• Vaginal Wet Mount
• Vaginal Yeast Infections

References

Citations

1. Joesoef MR, Schmid G (2005). Bacterial vaginosis, search date March 2004. Online version of BMJ Clinical Evidence. Also available online: http://www.clinicalevidence.com.
2. Hillier S, et al. (2008). Bacterial vaginosis. In KK Holmes et al., eds., Sexually Transmitted Diseases, 4th ed., pp. 737–768. New York: McGraw-Hill.
3. Centers for Disease Control and Prevention (2006). Diseases characterized by vaginal discharge section of Sexually transmitted diseases treatment guidelines. MMWR, 55(RR-11): 49–56.
4. U.S. Preventive Services Task Force (2008). Screening for bacterial vaginosis in pregnancy to prevent preterm delivery: U.S. Preventive Services Task Force recommendation statement. Annals of Internal Medicine, 148(3): 214–220.
5. Kessel KV, et al. (2003). Common complementary and alternative therapies for yeast vaginitis and bacterial vaginosis: A systematic review. Obstetrical and Gynecological Survey, 58(5): 351–358.
6. Marrazzo JM (2004). Evolving issues in understanding and treating bacterial vaginosis. Expert Review of Anti-Infective Therapy, 2(6): 913–922.

Other Works Consulted

• Abramowicz M (2007). Tinidazole (Tindamaz)—A new option for treatment of bacterial vaginosis. Medical Letter on Drugs and Therapeutics, 49(1269): 73–74.
• Abramowicz M (2007). Treatment guidelines: Drugs for sexually transmitted infections. Medical Letter on Drugs and Therapeutics, 5(61): 81–88.
• Ainbinder SW, et al. (2007). Sexually transmitted diseases and pelvic infections. In AH DeCherney et al., eds., Current Diagnosis and Treatment Obstetrics and Gynecology, 10th ed., p. 670. New York: McGraw-Hill.
• Mazdisnian F (2007). Benign disorders to the vulva and vagina. In AH DeCherney et al., eds., Current Diagnosis and Treatment Obstetrics and Gynecology, 10th ed., pp. 598–622. New York: McGraw-Hill.
• American College of Obstetricians and Gynecologists (2006, reaffirmed 2008). Vaginitis. ACOG Practice Bulletin No. 72. Obstetrics and Gynecology, 107(5): 1195–1206.
• Eckert LO, Lentz GM (2007). Infections of the lower genital tract. In VL Katz et al., eds., Comprehensive Gynecology, 5th ed., pp. 569–606. Philadelphia: Mosby Elsevier.
• Soper DE (2007). Genitourinary infections and sexually transmitted diseases. In JS Berek, ed., Berek and Novak's Gynecology, 14th ed., pp. 541–559. Philadelphia: Lippincott Williams and Wilkins.

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