Bacterial vaginosis (BV) discharge is typically thin and grayish-white or off-white. It can also appear slightly yellow in some cases. Unlike the thick, clumpy discharge of a yeast infection, BV discharge has a milklike consistency and tends to coat the vaginal walls evenly rather than clumping or collecting in patches.
What BV Discharge Looks Like
The hallmark of BV is a thin, homogeneous discharge that looks watery or milky. The color ranges from white to gray, sometimes with a slight yellowish tint. It spreads smoothly across the vaginal walls rather than appearing in thick patches or chunks. Many people notice it most on underwear or when wiping, where it may leave a grayish or dull-white streak.
The other defining feature isn’t the color but the smell. BV produces a distinct fishy odor caused by a chemical called trimethylamine, the same compound responsible for the smell of spoiling fish. This odor often becomes more noticeable after sex or during a period, because contact with semen or blood (both of which are more alkaline) releases more of the chemical into the air.
BV vs. Yeast Infection vs. Trichomoniasis
Color and texture are the fastest way to tell these three common vaginal infections apart at a glance:
- BV: Thin, off-white or grayish discharge with a fishy smell. Rarely causes itching.
- Yeast infection: Thick, white, cottage cheese-like discharge. Usually odorless but causes significant itching and irritation.
- Trichomoniasis: Profuse, yellow-green, frothy discharge with a strong unpleasant odor. Often comes with burning, redness, and soreness.
If your discharge is bright yellow, green, or frothy, that points away from BV and toward trichomoniasis or another infection that needs different treatment.
What Causes the Color Change
A healthy vagina is home to a population of beneficial bacteria that keep the environment acidic, with a pH between 4.0 and 4.5. BV happens when that balance shifts: the helpful bacteria decline and are replaced by an overgrowth of anaerobic bacteria. These bacteria raise the vaginal pH above 4.5, changing the chemistry of vaginal fluid.
That chemical shift is what alters both the color and the consistency of discharge. The overgrowth produces byproducts, including trimethylamine, that make the fluid thinner, more uniform, and slightly discolored compared to normal discharge. Normal discharge varies throughout the menstrual cycle from clear to white and changes in thickness, but BV discharge stays consistently thin and grayish.
How BV Is Diagnosed
You can’t diagnose BV from color alone, because normal discharge sometimes looks similar. Clinicians use a set of four criteria and look for at least three to confirm a diagnosis: the characteristic thin, milklike discharge; a vaginal pH above 4.5; a fishy odor (sometimes tested by adding a chemical solution to a sample); and the presence of “clue cells,” which are vaginal cells visibly coated with bacteria under a microscope.
A pH test alone isn’t definitive, since other infections also raise pH, but a pH at or below 4.5 makes BV unlikely. The combination of the grayish discharge, elevated pH, and fishy smell is what distinguishes BV from other conditions with similar-looking discharge.
Treatment and Recurrence
BV is treated with a course of antibiotics, either taken by mouth or applied as a vaginal gel or cream. Most people see the discharge and odor clear up within a few days of starting treatment. However, BV has a notoriously high recurrence rate. Studies show that up to 69% of women experience BV again within 12 months of completing standard treatment.
Recurrence doesn’t mean the treatment failed. It means the underlying bacterial balance is difficult to maintain for some people. Factors like a new sexual partner, douching, or hormonal shifts can tip the balance back toward overgrowth. If BV keeps returning, your provider may recommend a longer or different treatment approach.
Why It’s Worth Treating
BV sometimes resolves on its own, and many people with BV have no symptoms at all. But leaving it untreated carries real risks. BV increases susceptibility to sexually transmitted infections, including HIV, chlamydia, and gonorrhea. Those infections can in turn lead to pelvic inflammatory disease, which can affect fertility.
During pregnancy, untreated BV raises the risk of preterm birth and low birth weight (under 5.5 pounds). If you’re pregnant and notice thin, grayish, fishy-smelling discharge, getting tested is especially important.