Bacterial vaginosis is not dangerous, but it can cause disturbing symptoms. Any woman with an unusual discharge should be evaluated so that more serious infections, such as chlamydia and gonorrhea, can be excluded. Symptoms of bacterial vaginosis may also mimic those found in yeast infections of the vagina and other sexually transmitted diseases. But if anaerobic bacteria become too numerous, they upset the natural balance of microorganisms in your vagina and bacterial vaginosis results. 

Bacterial vaginosis can spread during sexual intercourse, but it also occurs in people who aren't sexually active. 

Bacterial vaginosis is a change in the balance of bacteria that are normally present in the vagina. Thevaginal discharge is thin and milky with a strong fishy odor. Many women have no symptoms. Bacterial vaginosis is not an STD.

Wet mount. A sample of the vaginal discharge is placed on a glass slide and mixed with a salt solution. The slide is looked at under a microscope for bacteria, yeast cells, trichomoniasis (trichomonads), white bloodcells that show an infection, or clue cells that show bacterial vaginosis.

Bacterial vaginosis signs and symptoms may include: 

Vaginal discharge that's thin and grayish white

Foul-smelling "fishy" vaginal odor, especially after sexual intercourse

Vaginal itching or irritation

Pain during intercourse

Burning during urination

Light vaginal bleeding

Risk factors for bacterial vaginosis include: 

Multiple sex partners or a new sex partner. The link between sexual activity and bacterial vaginosis isn't entirely clear, but bacterial vaginosis occurs more often in women who have multiple sex partners or a new sex partner. Bacterial vaginosis also seems to occur more frequently in women who have sex with women.

Douching. The practice of rinsing out your vagina with water or a cleansing agent (douching) upsets the natural balance of your vaginal environment. This can lead to an overgrowth of anaerobic bacteria, which in turn can result in bacterial vaginosis. Since the vagina is self-cleaning, douching isn't necessary.

IUD use. Women who use an intrauterine device (IUD) for birth control have a higher risk of bacterial vaginosis.

Black race. Black, non-Hispanic women are more likely to have bacterial vaginosis than are white women.

A natural lack of lactobacilli bacteria. If your natural vaginal environment doesn't produce enough of the "good" lactobacilli bacteria, you're more likely to develop bacterial vaginosis.

Generally, bacterial vaginosis doesn't cause complications. But under certain circumstances, having bacterial vaginosis may lead to: 

Preterm birth. In pregnant women, bacterial vaginosis is linked to premature deliveries and low birth weight babies.

Sexually transmitted infections. Having bacterial vaginosis makes women more susceptible to sexually transmitted infections, such as HIV, herpes simplex virus, chlamydia or gonorrhea. If you have HIV, bacterial vaginosis increases the odds that you'll pass the virus on to your partner.

Infection risk after gynecologic surgery. Having bacterial vaginosis may be associated with a greater chance of developing a post-surgical infection after procedures such as hysterectomy or dilation and curettage (D and C).

To treat bacterial vaginosis, your doctor may prescribe one of the following medications: 

Metronidazole (Flagyl, Metrogel-Vaginal, others). This medicine may be taken orally — as a pill that you swallow — twice a day for seven days. Metronidazole is also available for use topically, as a gel that you insert into your vagina for five to seven days. To avoid the potential for stomach upset, abdominal pain or nausea while using this medication, stay away from alcohol for the duration of the treatment.

Tinidazole (Tindamax). This medication is taken orally once a day for two to five days, depending on the prescription's strength. Tinidazole has the same potential for stomach upset and nausea as does oral metronidazole.

Clindamycin (Cleocin, Clindesse, others). This medicine is available as a cream that you insert into your vagina for seven days. One effect of using clindamycin cream is that it may weaken latex condoms, and that effect persists up to five days after you stop using the cream.

Take your medicine or use the cream or gel for as long as your doctor prescribes it — even if your symptoms go away. Stopping treatment early may increase the likelihood of recurrence. 

Despite the effective treatments for bacterial vaginosis, recurrence of symptoms within three to six months is common. Researchers are exploring the treatment regimens for recurrent bacterial vaginosis, but there's no evidence to support one therapy over another. If your symptoms recur soon after treatment, make an appointment with your doctor to discuss treatment options, one of which is extended-use metronidazole therapy. A self-help approach is lactobacillus colonization therapy — which attempts to boost the number of "good" bacteria in your vagina and re-establish a balanced vaginal environment — possibly accomplished by eating certain types of yogurt or other foods containing lactobacilli. 

To help prevent bacterial vaginosis: 

Minimize vaginal irritation. Stay out of hot tubs and whirlpool spas. Rinse soap from your outer genital area after a shower, and dry the area well to prevent irritation. Use mild, nondeodorant soaps and unscented tampons or pads.

Don't douche. Your vagina doesn't require cleansing other than normal bathing. Repetitive douching disrupts the normal organisms that reside in the vagina and can actually increase your risk of vaginal infection. Douching won't clear up a vaginal infection.

Avoid a sexually transmitted infection. Use a male latex condom, limit your number of sex partners, or abstain from intercourse to minimize your risk of a sexually transmitted infection.