Bacterial vaginosis, commonly called BV, is a vaginal condition caused by an imbalance between the “good” and “harmful” bacteria that naturally live in the vagina. It affects an estimated 23% to 29% of women of reproductive age worldwide, making it the most common vaginal condition in that age group. Despite how common it is, many women don’t recognize it or confuse it with a yeast infection, which requires completely different treatment.
What Happens Inside the Vagina
A healthy vagina contains a mix of bacteria collectively called vaginal flora. Normally, beneficial bacteria called lactobacilli dominate. These bacteria produce hydrogen peroxide and lactic acid, which keep the vaginal environment slightly acidic and inhospitable to harmful organisms. BV develops when lactobacilli decline and anaerobic bacteria (types that thrive without oxygen) multiply to take their place.
The key players in BV are two bacterial species that work together to form a sticky layer called a biofilm on the vaginal walls. This biofilm is one reason BV can be so stubborn. It protects the harmful bacteria from both the body’s defenses and from antibiotics, which helps explain why the condition so often comes back after treatment.
How BV Feels and What to Look For
About half of women with BV have no symptoms at all. When symptoms do appear, the most recognizable one is a thin, grayish-white vaginal discharge with a strong fishy smell. The odor is produced by chemicals that anaerobic bacteria release as they break down compounds in vaginal fluid, and it often becomes more noticeable after sex or during a period.
Unlike a yeast infection, BV rarely causes significant itching, redness, or swelling. The discharge also looks different: BV discharge tends to be thin and watery rather than thick and clumpy. If you’re experiencing thick, cottage cheese-like discharge with itching, that’s more likely a yeast infection. This distinction matters because over-the-counter yeast treatments won’t clear BV, and using them unnecessarily can further disrupt your vaginal flora.
What Raises Your Risk
BV is not a sexually transmitted infection, but sexual activity is one of the strongest risk factors. Having new or multiple sexual partners and not using condoms both increase your chances. The exact mechanism isn’t fully understood, but exposure to a new partner’s bacteria appears to shift the vaginal ecosystem enough to trigger an imbalance.
Douching is another major risk factor. The vagina is self-cleaning, and rinsing it with water, vinegar, or commercial douching products disrupts the bacterial balance that keeps it healthy. Douching washes away the protective lactobacilli, giving anaerobic bacteria room to take over. Other factors that can tip the balance include antibiotic use (which can kill off good bacteria along with the bad), hormonal changes, and smoking.
How BV Is Diagnosed
A healthcare provider can usually diagnose BV during a standard pelvic exam. The clinical approach involves checking for a few specific signs: the characteristic thin discharge, an elevated vaginal pH (above 4.5, higher than the normal acidic range), and the fishy odor that appears when a chemical solution is added to a sample of discharge. In a lab setting, a more precise method involves examining a vaginal swab under a microscope and scoring the types of bacteria present on a standardized 0-to-10 scale. A score of 7 or higher confirms BV, while 0 to 3 represents healthy flora.
Treatment Options
BV is treated with prescription antibiotics, either taken by mouth or applied directly inside the vagina as a gel or cream. Oral treatment is typically a seven-day course taken twice daily. The vaginal gel version is applied once a day for five days, while the vaginal cream is used at bedtime for seven days. Both approaches are effective, and your provider may recommend one over the other based on your preferences or whether you’re pregnant.
The vaginal formulations tend to cause fewer side effects like nausea, and some women prefer them for that reason. With oral antibiotics, you’ll need to avoid alcohol during treatment and for a day or two afterward, since the combination can cause severe nausea and vomiting.
Why BV Keeps Coming Back
Recurrence is the most frustrating aspect of BV. Between 50% and 80% of women who complete antibiotic treatment experience a return of symptoms within 6 to 12 months. That’s a strikingly high failure rate, and it’s largely because antibiotics kill the harmful bacteria but don’t rebuild the protective lactobacilli population. The biofilm that anaerobic bacteria create on the vaginal walls can also survive antibiotic treatment, seeding a new round of overgrowth once the medication stops.
For women dealing with repeated episodes, providers sometimes recommend longer or suppressive courses of treatment. There’s also growing interest in probiotics as a way to restore vaginal flora after antibiotics. Clinical trials have shown that certain strains of lactobacilli, taken either orally or applied vaginally, can help restore normal bacterial balance and reduce recurrences. In particular, strains of L. rhamnosus and L. acidophilus have shown the ability to inhibit the harmful bacteria that cause BV and promote regrowth of healthy flora. Results are promising but inconsistent across studies, so probiotics are generally used alongside standard treatment rather than as a replacement.
Potential Health Complications
BV isn’t just uncomfortable. Left untreated, it can increase your susceptibility to sexually transmitted infections, including HIV, chlamydia, and gonorrhea. The depletion of protective lactobacilli leaves the vaginal lining more vulnerable to pathogens that would otherwise struggle to gain a foothold.
During pregnancy, BV is associated with a higher risk of preterm birth and low birth weight. It can also increase the risk of infection after gynecological procedures like IUD insertion or surgery. These complications are why treatment is recommended even for women whose symptoms are mild or intermittent, and why screening for BV is part of prenatal care for women with a history of preterm delivery.
Reducing Your Risk
Since BV is fundamentally about bacterial balance, prevention centers on protecting the vaginal ecosystem. The most impactful steps are straightforward: avoid douching entirely, use condoms with new partners, and limit the use of scented soaps, sprays, or wipes in the vaginal area. Wearing breathable cotton underwear and changing out of wet swimwear or workout clothes promptly can also help maintain a healthy environment.
For women prone to recurrent BV, some providers recommend periodic probiotic use to maintain lactobacilli levels between episodes. While the evidence is still evolving, the logic is sound: keeping the population of protective bacteria high makes it harder for anaerobes to gain a foothold. The strains with the most clinical data behind them are L. rhamnosus GR-1, L. acidophilus, and L. fermentum RC-14, available in both oral supplements and vaginal formulations.