The most common symptom of bacterial vaginosis (BV) is a thin, off-white or gray vaginal discharge with a noticeable “fishy” smell. But more than half of all women with BV have no symptoms at all, which means the infection often goes undetected without a routine exam.
What BV Discharge Looks and Smells Like
BV discharge has a distinct profile that sets it apart from normal vaginal discharge. It’s typically thin and watery, with a milklike consistency that coats the vaginal walls smoothly rather than clumping. The color ranges from off-white to gray, and sometimes has a greenish tint.
The hallmark sign is a fishy odor. This smell tends to become stronger after sex, because semen is alkaline and reacts with the bacteria responsible for BV. Some women also notice the smell is more pronounced during their period, when menstrual blood similarly raises the vaginal pH. Outside of those triggers, the odor may be mild enough to miss entirely.
Other Symptoms You Might Notice
Beyond discharge, BV can cause a burning sensation during urination and mild itching around the outside of the vagina. These symptoms are usually less intense than what you’d experience with a yeast infection, and many women with BV don’t have itching at all. Some feel a general sense of irritation without being able to pinpoint it.
It’s worth noting that BV symptoms can come and go. You might have a few days of noticeable discharge, then nothing for a week. This intermittent pattern sometimes leads people to assume the problem resolved on its own, when the underlying bacterial imbalance may still be present.
How BV Feels Different From a Yeast Infection
BV and yeast infections are the two most common vaginal infections, and they’re easy to confuse. The key differences come down to discharge and itching.
- BV discharge is thin, grayish, foamy, and smells fishy.
- Yeast infection discharge is thick, white, clumpy (often compared to cottage cheese), and typically has no odor.
- Itching is the dominant symptom of a yeast infection, often intense. With BV, itching is mild or absent.
If you’re dealing with a strong smell but minimal itching, BV is more likely. If you have intense itching and thick white discharge but no odor, a yeast infection is the more probable cause. Getting the distinction right matters because they require completely different treatments. Over-the-counter antifungal creams won’t do anything for BV.
Why So Many Cases Go Unnoticed
More than half of women with BV experience no symptoms. This is partly because the shift in vaginal bacteria can be subtle enough that the body doesn’t mount a strong inflammatory response. Unlike a yeast infection or sexually transmitted infection, BV doesn’t typically cause redness, swelling, or significant pain. The vaginal lining usually looks normal even when the bacterial balance is off.
Asymptomatic BV still carries health risks. The bacterial imbalance can make you more susceptible to sexually transmitted infections and may contribute to complications during pregnancy, including preterm birth. This is one reason routine screening is sometimes recommended for pregnant women, even without symptoms.
What Happens During Diagnosis
A healthcare provider can usually identify BV through a combination of a pelvic exam and a few simple tests. The clinical approach looks at four factors: the appearance of the discharge, the vaginal pH, the presence of certain bacterial cells under a microscope, and whether the discharge produces a fishy smell when exposed to a chemical solution.
Normal vaginal pH sits below 4.5, which is slightly acidic. In BV, the pH rises above 4.5 because the protective bacteria that keep the environment acidic have been overtaken by other types. A pH test alone isn’t enough for a diagnosis, but it’s a strong clue. Under the microscope, a provider looks for “clue cells,” which are vaginal cells with so many bacteria stuck to their surface that the cell edges appear blurred or stippled. Seeing these cells is one of the most reliable indicators of BV.
Lab-based testing uses a scoring system that evaluates the ratio of healthy bacteria to BV-associated bacteria in a vaginal sample. A score of 0 to 3 indicates a normal bacterial balance, 4 to 6 falls into an intermediate range, and 7 to 10 confirms BV. The higher the score, the more the protective bacteria have been replaced by the types that cause symptoms.
What Causes the Bacterial Shift
BV isn’t caused by a single germ. It happens when the balance of bacteria naturally present in the vagina shifts, with protective species declining and other bacteria multiplying to fill the gap. The exact trigger for this shift isn’t fully understood, and researchers still don’t know precisely how sexual activity contributes, though having a new partner or multiple partners is a known risk factor.
Douching is one of the clearest modifiable risks. It disrupts the vaginal ecosystem by washing away protective bacteria and altering pH. Using scented soaps, bubble baths, or vaginal deodorants inside or around the vagina can have a similar effect. BV is not considered a sexually transmitted infection, but it’s more common in sexually active women and rarely occurs in those who have never had sex.