Both good and bad bacteria are present in a healthy vagina. Bacterial vaginosis (BV) occurs when these bacteria get out of balance. The number of good bacteria decreases. That allows the number of bad bacteria to increase. This results in BV. It's not a serious problem in most cases.

The cause of BV is not clear. Douching may lead to it. Having sex with a new partner or more than one partner makes it more likely.

Other causes include:

• Sharing sex toys.
• Not always using condoms or dental dams, or using these things the wrong way.

You can't get BV from toilet seats. You can't get BV from bedding or swimming pools.

The risk for BV is higher if:

• You are pregnant. This is because of the hormonal changes that happen during pregnancy.
• You use an intrauterine device (IUD). This is more likely if you use an IUD that is associated with irregular bleeding.

Symptoms vary for each person. Some people have few symptoms. Some have none at all. If there are symptoms, they can include:

• A thin, milky white or gray or sometimes green discharge.
• An unpleasant “fishy” odor.
• Irritation, itching, and burning at the opening of the vagina. This may mean it's caused by more than one type of bacteria.
• Burning or irritation with sex or when you urinate. This may mean it's caused by more than one type of bacteria.

Your doctor will ask about your symptoms and health history. The doctor will also do a pelvic exam. This is an exam of your vagina and cervix. They may take a sample of vaginal fluid or discharge. This will be looked at under a microscope for signs of BV. Sometimes the pH of vaginal fluid is tested.

BV is often treated with antibiotics. They may be given as a pill you take by mouth. Or it might be a vaginal cream. To use these medicines:

• Be sure to take all of your medicine, even if your symptoms go away.
• If you take antibiotic pills, don't drink alcohol until you're finished with all of your medicine.
• If you use a vaginal cream, apply it as directed. Be aware that the cream may make condoms and diaphragms less effective.
• Contact your doctor if symptoms don't go away within 4 days of starting treatment. And contact the doctor if you have a reaction to the medicine.

Treatment for your sexual partner:

• Ask your doctor if any sex partners may need treatment. It may help reduce the risk of bacterial vaginosis coming back.

To help prevent BV:

• Limit the number of sex partners.
• Don't douche.
• Use condoms and dental dams in the right way every time you have sex.
• Keep the vaginal bacteria balanced. Use only warm water to clean the outside of the vagina. Even mild soap can irritate the vagina. Always wipe front to back from the vagina toward the anus. Keep the area cool by wearing cotton or cotton-lined underpants.

BV should be treated even if you have no symptoms or your symptoms are mild. BV that isn't treated can lead to health problems. They include an increased risk for:

• Preterm delivery or spontaneous abortion if you are pregnant.
• Complications after surgery on the reproductive organs.
• Getting other STIs. Two examples are chlamydia and gonorrhea.
• Getting or transmitting HIV.
• Infection or reactivation of the human papillomavirus.

And there may be a possible increased risk for pelvic inflammatory disease.