Grey vaginal discharge is most commonly a sign of bacterial vaginosis (BV), the most common vaginal infection in women of reproductive age. The discharge is typically thin, has a milk-like consistency, and often comes with a noticeable fishy odor, especially after sex. While it can be alarming to notice, BV is treatable and not considered a sexually transmitted infection.
Why the Discharge Looks Grey
A healthy vagina is home to large numbers of beneficial bacteria called lactobacilli, which keep the environment slightly acidic. When certain other bacteria begin to multiply and overtake them, the balance shifts. One bacterium in particular starts the process by lowering oxygen levels inside the vagina, creating conditions where other bacteria that normally exist in very small numbers can thrive. These bacteria form a film that clings to the vaginal walls.
As these bacteria grow, they break down proteins into amino acids and produce waste products, including ammonia and compounds called amines. These byproducts are what give the discharge its greyish or off-white color and its characteristic fishy smell. The ammonia also raises the vaginal pH above its normal slightly acidic range, which makes the environment even less hospitable to the healthy bacteria that would normally keep things in check. This creates a self-reinforcing cycle that won’t resolve without intervention.
What Grey Discharge Feels Like
Many people with BV have no symptoms at all. When symptoms do appear, the most common ones are:
- Thin, white or grey discharge that coats the vaginal walls evenly
- A strong fishy odor that becomes more noticeable after sex or during your period
- Mild irritation or itching around the vaginal opening, though this is less common than with yeast infections
The discharge itself tends to be watery or milky rather than thick or clumpy. If your discharge is thick, cottage cheese-like, or bright white, a yeast infection is more likely. If it’s yellow-green, frothy, or accompanied by painful urination and significant irritation, a different infection called trichomoniasis may be the cause. Trichomoniasis can also produce a fishy smell, which is why the appearance and texture of the discharge matters when distinguishing between the two.
What Increases Your Risk
BV is not caused by poor hygiene. In fact, one of the biggest risk factors is over-cleaning. Women who douche are roughly four times more likely to develop abnormal vaginal discharge compared to women who don’t. Douching washes away protective bacteria and disrupts the natural pH balance, making it easier for the wrong bacteria to take hold.
Other common risk factors include having a new sexual partner or multiple partners, using scented soaps or products inside the vagina, and smoking. Hormonal changes can also play a role. BV can develop in anyone with a vagina, including people who have never had sex, though it’s more common in sexually active women.
Grey Discharge During Pregnancy
If you’re pregnant and notice grey discharge, it’s worth getting checked promptly. People with BV during pregnancy may be more likely to deliver preterm, meaning before 37 weeks. Preterm delivery carries serious risks for the baby, including breathing problems and other complications. The relationship between BV and preterm birth isn’t fully understood, as it’s unclear whether BV directly causes early delivery or is associated with it through other factors. Regardless, treatment during pregnancy is straightforward and can reduce potential risks.
How BV Is Diagnosed
A healthcare provider can usually diagnose BV during a standard pelvic exam. The clinical criteria involve checking for a thin, homogeneous discharge, testing whether vaginal pH is above 4.5, looking for bacterial cells clinging to vaginal skin cells under a microscope, and checking for a fishy odor. Meeting three of these four criteria confirms the diagnosis.
You can also buy over-the-counter vaginal pH test strips. The FDA notes that these home tests show good agreement with a doctor’s diagnosis, but they have limitations. An elevated pH can occur for reasons other than BV, and a normal pH doesn’t necessarily rule out infection. The test can’t tell you which type of infection you have. It’s a reasonable first step if you’re unsure whether something is off, but it’s not a substitute for a full evaluation.
Treatment and What to Expect
BV is treated with antibiotics, available either as oral pills or vaginal gels or creams. Treatment typically clears the infection within a week. Symptoms often improve within a few days of starting medication.
The bigger challenge with BV is recurrence. Between 50 and 80 percent of women experience a return of BV within 12 months of finishing antibiotic treatment. This high recurrence rate is partly because antibiotics kill the overgrown bacteria but don’t necessarily restore the protective lactobacilli. The bacterial film that clings to vaginal walls can also be difficult to fully eliminate, allowing the cycle to restart.
To reduce the chances of recurrence, avoid douching and scented vaginal products entirely. Some providers recommend probiotics or extended courses of treatment for people who experience frequent episodes, though evidence on long-term prevention strategies is still evolving. If your grey discharge keeps coming back after treatment, that pattern itself is worth discussing with your provider, as it may warrant a different management approach than a one-time episode.