Bacterial vaginosis (BV) causes a thin, fishy-smelling vaginal discharge, though nearly half of people with BV have no symptoms at all. When symptoms do appear, the smell and discharge are the most recognizable signs, but BV can also cause itching and burning that overlap with other vaginal infections.
The Hallmark Sign: Fishy-Smelling Discharge
The most distinctive BV symptom is a vaginal discharge with a strong “fishy” odor. The discharge is typically thin and milklike in consistency, coating the vaginal walls smoothly rather than clumping. Its color ranges from off-white to gray or greenish.
The smell often becomes more noticeable after sex. That’s because semen is alkaline, which raises vaginal pH and releases more of the odor-causing compounds produced by the bacteria behind BV. Some people notice the smell is strongest during their period for the same reason: menstrual blood also shifts vaginal pH upward.
A healthy vagina is naturally acidic, with a pH below 4.5. Protective bacteria produce lactic acid that keeps the environment inhospitable to harmful organisms. When those bacteria are outnumbered, the pH rises above 4.5, and the conditions that cause BV take hold.
Other Symptoms Beyond Discharge
While the odor and discharge get the most attention, BV can also cause vaginal itching and a burning sensation during urination. These symptoms tend to be milder than what you’d experience with a yeast infection, where intense itching and vulvar swelling are more common. Still, the irritation can be persistent and uncomfortable.
BV does not typically cause significant redness, swelling, or pain inside the vagina. If you’re experiencing those symptoms alongside discharge, a different infection or a co-infection may be involved.
When There Are No Symptoms at All
Roughly half of people with BV are completely asymptomatic. One study of 470 patients diagnosed with BV found that 48% had no noticeable symptoms. This is a major reason BV often goes undetected. You can carry the bacterial imbalance for weeks or longer without realizing anything has changed.
Asymptomatic BV isn’t necessarily harmless. The same pH shift and bacterial overgrowth are present whether you feel symptoms or not. During pregnancy, untreated BV has been linked to complications, which is why screening is sometimes done even without symptoms.
How BV Feels Different From a Yeast Infection
BV and yeast infections are the two most common causes of abnormal vaginal discharge, and many people confuse them. The differences are fairly reliable once you know what to look for:
- Discharge texture: BV produces thin, watery, foamy discharge. Yeast infections produce thick, white, clumpy discharge often compared to cottage cheese.
- Smell: BV has a distinct fishy odor. Yeast infections are usually odorless.
- Itching: Yeast infections cause intense itching and sometimes visible swelling of the vulva. BV may cause mild itching, but it’s rarely the dominant symptom.
- Color: BV discharge tends to be grayish or greenish. Yeast discharge is typically white.
These patterns hold for most people, but overlap exists. Using an over-the-counter yeast treatment when you actually have BV won’t help and can delay proper care.
What Makes Symptoms Flare
Certain activities can worsen BV symptoms or trigger a recurrence. Douching is one of the most well-documented risk factors. It strips away the protective bacteria that keep vaginal pH low, creating an opening for BV-associated organisms to overgrow. Research has consistently shown that douching disrupts normal vaginal flora and may predispose the vagina to colonization by harmful bacteria.
Unprotected sex is another common trigger. Semen temporarily raises vaginal pH, and new sexual partners can introduce unfamiliar bacteria. BV isn’t classified as a sexually transmitted infection, but sexual activity clearly plays a role in its development and recurrence. Scented soaps, bubble baths, and fragranced hygiene products applied near the vagina can also shift the bacterial balance.
How Doctors Confirm It’s BV
Diagnosis is straightforward. Clinicians use a set of criteria that checks for at least three of four signs: a thin, homogeneous discharge, a vaginal pH above 4.5, the presence of “clue cells” under a microscope, and a fishy odor when the discharge is exposed to a chemical solution. Clue cells are vaginal skin cells covered in a layer of bacteria, and they’re one of the most reliable markers of BV.
The pH test is simple and fast, which is why some at-home vaginal health kits include pH strips. A reading above 4.5 doesn’t confirm BV on its own (other infections also raise pH), but a reading below 4.5 makes BV unlikely and points more toward a yeast infection.
Symptom Duration and Recurrence
BV sometimes resolves on its own, but there’s no reliable timeline for that. Symptoms can persist for weeks or fluctuate in intensity, improving for a few days and then returning. Without treatment, the bacterial imbalance tends to linger rather than clear up quickly.
Recurrence is one of the most frustrating aspects of BV. Many people experience repeat episodes within months of successful treatment. The underlying reasons aren’t fully understood, but reinfection from a sexual partner, persistent biofilms of bacteria on the vaginal walls, and the same lifestyle triggers (douching, new partners, fragranced products) all play a role. If your symptoms keep coming back, that pattern itself is useful information to bring to a healthcare provider.