Bacterial vaginosis (BV) is a vaginal condition caused by an imbalance between the “good” and “harmful” bacteria that naturally live in the vagina. It’s the most common vaginal condition among women of reproductive age, and despite how often it occurs, researchers still don’t fully understand what triggers it. Here’s what we do know.
What Happens Inside the Vagina During BV
A healthy vagina is home to large numbers of bacteria called lactobacilli. These are the good guys. They produce hydrogen peroxide, which keeps the vaginal environment slightly acidic and makes it harder for harmful organisms to take hold. Think of them as a natural defense system.
When BV develops, the lactobacilli population drops sharply, and various anaerobic bacteria (organisms that thrive without oxygen) multiply to fill the gap. This shift raises the vaginal pH, making it less acidic. The result is an overgrowth of harmful bacteria that produces the hallmark symptoms of BV. It’s not a single “bug” causing the problem. BV is what researchers call a polymicrobic infection, meaning multiple bacterial species work together to create the imbalance.
How You Get BV
This is where things get frustratingly vague. The CDC states plainly: researchers do not know the exact cause of BV. They also don’t know exactly how sex contributes to it. What is clear is that certain activities increase your risk:
- New or multiple sexual partners. BV happens more often in people with different or new partners, though the biological reason isn’t well understood. BV is not classified as a sexually transmitted infection, but sexual activity is closely linked to it.
- Douching. Rinsing the inside of the vagina disrupts the balance of healthy bacteria and can trigger an overgrowth of anaerobes.
- Not using condoms. Unprotected sex appears to increase the chances of bacterial disruption.
- Naturally low lactobacilli levels. Some people simply don’t produce enough protective bacteria, which makes them more susceptible regardless of other factors.
BV can develop without any sexual activity at all, though it rarely affects people who have never had sex. This gray area is part of why it’s so poorly understood compared to straightforward infections with a single identifiable cause.
What BV Feels and Looks Like
Many people with BV have no symptoms at all. When symptoms do appear, the most common ones are a thin, grayish-white vaginal discharge and a noticeable fishy odor, especially after sex. The smell comes from chemicals produced by the anaerobic bacteria as they multiply. Some people also experience mild itching or irritation, but BV typically doesn’t cause the intense itching or thick, clumpy discharge associated with yeast infections.
If you’re unsure whether what you’re experiencing is BV or something else, the discharge characteristics are a useful clue. BV discharge tends to be thin, even, and coating rather than chunky. The odor is the most distinctive feature and often what prompts people to seek care.
Why BV Shouldn’t Be Ignored
BV sometimes resolves on its own, but leaving it untreated can carry real health consequences. It increases susceptibility to sexually transmitted infections, including HIV. During pregnancy, untreated BV raises the risk of preterm birth and low birth weight. It can also lead to pelvic inflammatory disease, which affects the uterus and fallopian tubes and can complicate fertility. These risks make it worth addressing even when symptoms feel mild or manageable.
How BV Is Treated
BV is treated with prescription antibiotics. The most common option is a seven-day course of oral pills taken twice daily. There are also vaginal gel and cream versions applied with an applicator, typically for five to seven days. Your provider will recommend one based on your preferences and medical history. Treatment usually clears the infection within a week or two.
The bigger challenge is recurrence. Between 50% and 80% of women experience BV again within 6 to 12 months of finishing antibiotic therapy. This high recurrence rate is one of the most frustrating aspects of the condition and is an active area of medical research. Some providers recommend extended or suppressive antibiotic regimens for people dealing with repeated episodes.
Reducing Your Risk
Since the exact cause isn’t known, prevention focuses on protecting the vaginal environment from disruption. The most important step is avoiding douching entirely. The vagina cleans itself, and introducing water or solutions inside it does more harm than good.
Beyond that, practical habits make a difference. Use condoms during sex. Wash the vulva (the outside only) with mild, unscented soap or plain water. Skip scented tampons, pads, vaginal sprays, and scented toilet paper, all of which can irritate the area and shift bacterial balance. Wear cotton underwear and change out of wet swimsuits or sweaty exercise clothes promptly. Change tampons every two to four hours.
These steps won’t guarantee you’ll never develop BV, especially if you’re someone whose body naturally produces fewer lactobacilli. But they reduce the environmental triggers that make an imbalance more likely and give your natural defenses the best chance of holding steady.