BV, or bacterial vaginosis, is the most common vaginal infection in women of reproductive age. It happens when the balance of bacteria inside the vagina shifts, replacing the healthy bacteria that normally keep things in check with an overgrowth of other organisms. BV is not a sexually transmitted infection, though sexual activity can play a role in triggering it.
What Happens Inside the Vagina
A healthy vagina is dominated by bacteria called Lactobacillus. These bacteria produce lactic acid, which keeps the vaginal environment slightly acidic and inhospitable to harmful organisms. In BV, Lactobacillus populations drop dramatically and get replaced by a mixture of other bacteria, including Gardnerella vaginalis and various oxygen-avoiding species. This shift raises the vaginal pH, making it less acidic, and creates the conditions responsible for BV symptoms.
The exact trigger for this bacterial shift isn’t fully understood. Known risk factors include douching, having a new sexual partner or multiple partners, and using scented soaps or products inside or around the vagina. Anything that disrupts the natural bacterial balance can set the stage for BV. Some women develop it without any obvious cause.
Common Symptoms
The hallmark of BV is a thin, off-white vaginal discharge with a noticeable “fishy” smell. The odor tends to be strongest after sex or during a menstrual period. Unlike a yeast infection, BV typically doesn’t cause intense itching or thick discharge. Some women experience mild irritation or burning during urination, but many women with BV have no symptoms at all and only find out during a routine exam.
BV vs. Yeast Infection vs. Trichomoniasis
These three conditions are the most common causes of abnormal vaginal discharge, and they’re easy to confuse. The differences come down to what the discharge looks like and what other symptoms accompany it.
- Bacterial vaginosis: Thin, off-white discharge with a fishy odor. Itching is usually mild or absent.
- Yeast infection: Thick, white, cottage cheese-like discharge. Strong vaginal itching is the primary complaint, and there’s typically no strong odor.
- Trichomoniasis: Profuse, yellow-green, frothy discharge with a foul smell. Itching, burning, and redness are common. This one is a sexually transmitted infection caused by a parasite.
Because the symptoms overlap, getting the right diagnosis matters. BV and trichomoniasis require different treatments, and using an over-the-counter yeast infection cream won’t help either one.
How BV Is Diagnosed
A healthcare provider can usually diagnose BV during a pelvic exam. They’ll look at the discharge, check the vaginal pH (which is higher than normal in BV), and may examine a sample under a microscope to look for “clue cells,” which are vaginal cells coated with bacteria. A “whiff test,” where a chemical solution is added to a discharge sample to see if it produces a fishy odor, is another common part of the evaluation. Some clinics also use molecular tests that can identify BV-associated bacteria from a vaginal swab.
Treatment
BV is treated with prescription antibiotics, either taken by mouth or applied inside the vagina as a gel or cream. The oral option is typically a seven-day course taken twice daily. Vaginal gel or cream is applied once daily for five to seven days, usually at bedtime. Both approaches work well, and your provider will help you choose based on your preference and medical history.
Symptoms often improve within a few days of starting treatment, but it’s important to finish the full course even if you feel better. Stopping early increases the chance that the infection comes back.
Why BV Keeps Coming Back
Recurrence is one of the most frustrating aspects of BV. Up to 66% of women experience a recurrence within a year of treatment, according to the American College of Obstetricians and Gynecologists. The bacteria responsible for BV can form protective layers, called biofilms, on the vaginal wall that antibiotics don’t fully eliminate. Sexual partners may also carry BV-associated bacteria, reintroducing them after treatment.
In a notable shift, ACOG now recommends considering concurrent treatment for male sexual partners of women with recurrent BV, using a combination of oral and topical antibiotics. This is the first time the organization has made this recommendation, reflecting growing evidence that BV can be passed back and forth between partners. For women with same-sex partners, shared decision-making about partner treatment is also encouraged.
Probiotics are another area of interest. A study of 228 women found that those who used a vaginal probiotic containing Lactobacillus crispatus twice per week after standard antibiotic treatment had a 30% recurrence rate by week 12, compared with 45% in the placebo group. It’s a meaningful difference, though probiotics alone aren’t a replacement for antibiotics when an active infection is present.
Potential Complications
BV isn’t just uncomfortable. It raises the risk of acquiring sexually transmitted infections, including HIV, chlamydia, and gonorrhea. The disrupted bacterial environment and higher pH make the vaginal lining more vulnerable to infection.
During pregnancy, BV is linked to premature birth and low birth weight. Pregnant women with symptoms of BV should be evaluated and treated, since addressing the infection reduces these risks. BV can also increase the chance of developing an infection after gynecological surgery, including procedures like a hysterectomy or an IUD insertion.
Reducing Your Risk
The vagina is self-cleaning, and the simplest prevention strategy is to avoid disrupting its natural balance. That means skipping douches entirely, as they wash out protective bacteria and are one of the strongest risk factors for BV. Avoid scented tampons, pads, sprays, and soaps in the vaginal area. When washing, warm water alone or a mild, unscented soap on the outer vulva is sufficient.
Using condoms consistently can also lower BV risk by reducing the introduction of outside bacteria. Wearing breathable, cotton underwear and changing out of wet swimsuits or workout clothes promptly helps keep the vaginal environment stable. None of these steps guarantee prevention, but they collectively support the conditions that allow Lactobacillus to thrive.