What Is Bacterial Vaginosis And How Do You Get It?

Bacterial vaginosis (BV) is the most common vaginal condition in women of childbearing age. It happens when the normal balance of bacteria in the vagina shifts, and certain types of bacteria grow more than they should. You get it when this natural balance is disrupted, though the exact trigger for that disruption is not always clear. It is not a sexually transmitted infection, but sexual activity can increase your risk of developing it.

What Is Bacterial Vaginosis And How Do You Get It?

Bacterial vaginosis is an imbalance of the naturally occurring bacteria in the vagina. A healthy vagina is dominated by Lactobacillus bacteria, which produce lactic acid and hydrogen peroxide. These keep the environment acidic and prevent other bacteria from overgrowing. When Lactobacillus levels drop, other bacteria like Gardnerella vaginalis and various anaerobes multiply rapidly. That overgrowth is BV.

The condition is not caused by poor hygiene, and it is not a classic infection passed between partners. It is a disruption of an ecosystem. Anything that changes the vaginal pH or the bacterial community can allow this shift to happen. Douching is a well-documented trigger because it washes away the protective Lactobacillus. Using scented soaps, bubble baths, or intimate sprays can also irritate the area and disturb the balance.

Sexual activity plays a role, especially with a new partner or multiple partners. Semen has a higher pH than the vagina, and this can temporarily reduce acidity. Some research suggests that the bacteria associated with BV can be introduced through sexual contact, though it is not considered an STI in the traditional sense. Women who have never been sexually active can still develop BV, which is why the condition is not classified as a sexually transmitted infection.

What Are The Symptoms Of Bacterial Vaginosis?

Up to half of women with BV have no symptoms at all. When symptoms do appear, the most common is a thin, white or gray vaginal discharge. The discharge often has a strong fishy odor, which may be more noticeable after sex or during menstruation. This odor happens because the overgrown bacteria produce chemicals called amines, which become more volatile when the pH rises.

Some women experience mild itching or irritation around the vagina, and some notice burning during urination. The symptoms can fluctuate over time. They may be worse at certain points in the menstrual cycle and less noticeable at others. If you have any of these symptoms, it is worth seeing a clinician for an accurate diagnosis, because other conditions like yeast infections or trichomoniasis can look similar.

It is important not to self-diagnose. Yeast infections cause thick, white, cottage-cheese-like discharge and intense itching, while BV discharge is typically thinner and has an odor. The treatments are completely different. Using an antifungal cream for BV will not help, and using antibiotics for a yeast infection can make it worse.

How Is Bacterial Vaginosis Diagnosed?

A clinician can usually diagnose BV during a pelvic exam. They take a sample of the discharge and check the pH level. A normal vaginal pH is between 3.8 and 4.5. In BV, the pH is typically above 4.5. The sample is also examined under a microscope to look for clue cells, which are vaginal skin cells covered with bacteria. The presence of clue cells along with a high pH and a fishy odor when potassium hydroxide is added confirms the diagnosis.

This set of criteria is called Amsel’s criteria. A diagnosis requires at least three of the four findings: thin white discharge, clue cells on microscopy, vaginal pH above 4.5, and a fishy odor after adding potassium hydroxide. Some clinics also use a test called a Gram stain, which grades the bacterial community on a scale. This is more accurate but is mostly used in research settings.

There is no home test that is as reliable as a clinical evaluation. At-home pH swabs exist, but they cannot distinguish BV from other infections that also raise pH, such as trichomoniasis. If you suspect BV, a clinical visit is the safest route.

What Are The Risks If BV Is Left Untreated?

BV can resolve on its own, but it often does not. When it persists, the main concern is increased susceptibility to other infections. The protective Lactobacillus barrier is compromised, which makes it easier for sexually transmitted infections like HIV, herpes, and chlamydia to establish themselves. The risk of acquiring an STI is higher in women with untreated BV.

In pregnancy, BV carries additional risks. Research consistently shows that untreated BV is associated with preterm birth and low birth weight. The exact mechanism is not fully understood, but the ascending bacteria may trigger an inflammatory response that leads to early labor. For this reason, many clinicians screen pregnant women with symptoms and treat BV to reduce these risks.

BV can also increase the risk of pelvic inflammatory disease (PID) after procedures like an IUD insertion or endometrial biopsy. PID is an infection of the upper reproductive tract that can damage the fallopian tubes and affect fertility. Treating BV before these procedures is standard practice in many clinics.

How Is Bacterial Vaginosis Treated?

BV is treated with prescription antibiotics. The two most common are metronidazole and clindamycin. Metronidazole is available as an oral tablet or a vaginal gel. Clindamycin is available as a vaginal cream or ovule. Both are highly effective, with cure rates around 80 percent after one course of treatment.

Oral metronidazole is typically taken twice daily for seven days. The vaginal gel is used once daily for five days. Clindamycin cream is used once daily for seven days. It is important to complete the full course even if symptoms improve. Stopping early can allow the bacteria to rebound and may contribute to recurrence.

Alcohol must be avoided while taking oral metronidazole and for 48 hours after the last dose. Combining them can cause severe nausea, vomiting, and flushing. Clindamycin cream is oil-based, so it can weaken latex condoms and diaphragms. Use alternative contraception during treatment and for five days after finishing the cream.

There is no over-the-counter treatment for BV. Products marketed for “feminine hygiene” or “pH balance” have not been shown to cure BV. Probiotics are sometimes discussed as an adjunct, but the evidence is mixed. Some studies suggest that Lactobacillus-containing probiotic suppositories may help prevent recurrence, but no large trials have confirmed the optimal strain or dose. Oral probiotics have not been consistently shown to help.

Why Does BV Keep Coming Back?

Recurrence is the most frustrating part of BV. Within three to six months, about 30 to 50 percent of women experience another episode. The reasons are not fully understood. It may be that the Lactobacillus community never fully recovers after the first episode, or that the BV-associated bacteria persist in a biofilm that resists antibiotics.

A biofilm is a thin, sticky layer of bacteria that attaches to the vaginal wall. Gardnerella vaginalis is known to form biofilms, and these can protect the bacteria from antibiotics and the immune system. This may explain why oral or vaginal antibiotics work initially but fail to prevent recurrence.

Some clinicians recommend a longer course of antibiotics or suppressive therapy for women with frequent recurrences. This means taking a lower dose of metronidazole gel twice weekly for several months. This approach can reduce recurrences while the treatment is ongoing, but symptoms often return once it stops. There is no cure for recurrent BV, and management is about controlling episodes rather than eliminating the condition permanently.

Reducing known triggers can help. Stopping douching, avoiding scented products, and using condoms consistently have all been associated with lower recurrence rates. The evidence for these measures is observational, not from randomized trials, but the logic is sound and the risk of harm is minimal.