Vaginal odor is one of the top reasons people seek medical care for vaginal health concerns, yet science has historically failed to understand what causes it fully. While bacterial vaginosis (BV) has long been linked with odor, research has yet to identify which bacterial strains are actually responsible for vaginal odor, or their underlying biological mechanisms.

So, we did something about it. Using real-world samples from Evvy users, we conducted the largest study ever on vaginal odor. The research, published in the American Journal of Obstetrics & Gynecology,, analyzed the vaginal microbiomes of 6,585 non-menopausal women who took Evvy’s Vaginal Health Test. By leveraging shotgun metagenomic sequencing—the same cutting-edge technology we use in our test—we linked specific bacterial species with odor severity and even identified a gene that fuels odor production.

This study is just one example of how Evvy is using the largest real-world dataset on the vaginal microbiome to close critical knowledge gaps in female health.

Here’s what Evvy’s groundbreaking research found: 

  • Odor varies in severity and description. While “fishy” was the most common descriptor (32%), other descriptions were widely reported, highlighting that odor isn’t a one-size-fits-all symptom. No two vaginas are alike, and neither is the way they smell!
  • Eight bacterial species were linked to odor severity. The study identified Prevotella, Megasphaera, Porphyromonas, and Finegoldia among the bacteria most strongly associated with unusual vaginal odor.
  • Odor severity isn’t always linear. While bacterial abundance increased with odor severity, there was no significant difference between moderate and severe cases, suggesting a tipping point where other factors may play a role.‍
  • Putrescine production is a key biological driver of odor. The putrescine pathway, which produces odorous compounds, was detected in 14% of people with severe odor — compared to just 2% of asymptomatic people.
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Why this study matters

Vaginal odor is an incredibly common concern. Women and people assigned female at birth are often brought up to believe that vaginas should be odorless, which creates unnecessary stigma and makes it harder to discern what normal and abnormal vaginal odor is. 

Furthermore, unusual vaginal odor is often a key indicator of infection but often gets lumped under the category of dysbiosis, without further investigation. Until recently, experts failed to identify the bacteria responsible for vaginal odor, meaning that adequate treatment was a shot in the dark. 

This is the first — and largest — study to pinpoint specific bacterial taxa linked to odor severity, moving beyond general BV diagnoses. Evvy’s research highlights that not all vaginal odors are the same, which could help improve diagnostics and treatment.

Specifically, the identification of the putrescine pathway as a potential biological mechanism provides a new target for more effective odor-reducing treatments.

Vaginal odor as a concern has a direct impact on women’s quality of life. It can lead to poor body image and self-esteem, to the point where women with BV often feel too self-conscious to engage in sexual activities, sometimes withdrawing from sex altogether. A lack of understanding (and adequate treatment) for vaginal odor means many turn to ineffective, harmful practices, such as using vaginal douches or scented feminine hygiene products — a vicious cycle that can make the issue worse. Evvy’s research is an important piece in the puzzle of uncovering how the vaginal microbiome works, and the direct effect that has on women’s lives.

How does Evvy conduct research like this?

Every discovery we make is only possible because of our incredible community. When Evvy users choose to contribute their anonymized test data to research, they help us uncover groundbreaking insights — like what actually causes vaginal odor. By building the largest real-world dataset on the vaginal microbiome, we’re able to push science forward and close critical gaps in female health. Participation is always optional, and privacy is our top priority. Thank you to all the Evvy users who contributed their data to research. We couldn’t have done it without you!