Does your period product affect vaginal health?

Every month, millions of people around the world reach for pads, tampons, menstrual cups, and other period products.

Yet despite being among the most widely used health products globally, we still know surprisingly little about how they may interact with the vaginal microbiome. 

That's a major gap, especially considering most sit directly against, or inside, one of the body's most delicate and important microbial ecosystems.

To help change this, we recently launched IMVAHA (Improving Menstrual and VAginal Health for All), a multinational citizen science study investigating how pads, tampons, and menstrual cups may influence vaginal health (1). 

Led by Dr. Sonja Merten at the Swiss Tropical and Public Health Institute and funded by the Swiss Network for International Studies and the Gates Foundation, IMVAHA brings together participants from Switzerland, Peru, and Cameroon to help answer the question:

Do different menstrual products affect the vaginal microbiome in different ways?

Why study menstrual products and vaginal health?

The vagina is home to a dynamic community of microorganisms known as the vaginal microbiome. Its composition may play an important role in maintaining reproductive and urogenital health. 

In people with a healthy vaginal microbiome, beneficial bacteria like Lactobacillus often dominate. These bacteria help maintain a low vaginal pH and create a protective environment (2).

When this balance shifts—a state known as dysbiosis—beneficial bacteria decline and other bacteria, such as Dialister, become more dominant.

Dysbiosis has been associated with an increased risk of a range of health issues, including bacterial vaginosis, sexually transmitted infections (STIs), pregnancy complications, and infertility (1).

At the same time, research has shown that there is no single "normal" vaginal microbiome. Healthy people can have very different microbial communities, shaped by a range of biological, behavioral, and environmental factors (3,4).

These include diet, sexual activity, stress, smoking, medication use (including antibiotics and contraceptives), and hormonal changes, such as during the menstrual cycle.

Yet one potential influence remains surprisingly understudied: the menstrual products people use every month.

What we know so far

One of the largest studies to date, conducted through the Isala project in Belgium, analyzed vaginal samples from over 3,000 participants and found that pad use was associated with bacteria linked to vaginal dysbiosis, while tampon and menstrual cup use was linked with higher levels of beneficial bacteria (5). 

While this study was an important first step, it was observational, meaning it could show that differences existed between users of different products, but not whether the products themselves caused those differences.

To answer that question, we need a different kind of study.

How the IMVAHA study works

IMVAHA is being conducted simultaneously in Switzerland, Peru, and Cameroon, allowing us to explore whether findings are consistent across different populations, cultures, and menstrual product practices.

A total of 300 participants will take part. Over the course of the study, each participant will use pads, tampons, and menstrual cups, with the order assigned randomly. 

Because every participant uses all three products, each person serves as their own comparison. This allows us to more directly assess whether differences in the vaginal microbiome are associated with the menstrual product being used.

Each product will be used for two menstrual cycles before switching to the next.

Two to three days after each period, participants will collect a vaginal swab and complete a short survey about their symptoms, menstrual experiences, and hygiene practices.

The samples are then analyzed to assess the vaginal microbiome, vaginal pH, and the presence of bacteria associated with toxic shock syndrome.

Why real-world data is the future of menstrual product safety research

Studying how menstrual products influence vaginal health requires following participants over multiple menstrual cycles and collecting samples repeatedly over time. Doing that entirely through clinic visits would be challenging for both participants and researchers.

Instead, IMVAHA enables participants to collect samples themselves at home and contribute directly to the research process. This approach makes participation more accessible, allows us to study vaginal health in real-world settings, and makes it possible to include larger and more diverse populations than would typically be feasible in a clinic-based study.

IMVAHA is part of the Isala Sisterhood, a global network of researchers working to deepen our understanding of vaginal health. It grew out of the original Isala study on the vaginal microbiome, launched in 2020 at the University of Antwerp in Belgium.

Research teams around the world were inspired by it and started their own citizen-science projects on the topic. Together, they share methods, tools, and findings across countries in the Global North and Global South. This brings much-needed diversity to vaginal microbiome research.

Why this research matters

Over time, evidence from IMVAHA could influence how menstrual products are developed, evaluated, and regulated.

The findings will be shared through a broad network of partners—including WHO, UNFPA, ISO, and Clue—to support future research, policy development, and public understanding of menstrual product safety and vaginal health.

But perhaps most importantly, this research will help provide people with better information about products they use every month and support more informed choices about their menstrual health.

Learn more

The full IMVAHA study protocol has now been published, providing a detailed overview of the study design and research methods.

You can also learn more about the Isala Sisterhood and related projects:

• Isala Sisterhood: isala.be

• IMVAHA: imvaha.org

• Marie Project (Switzerland): marie-project.ch

• Proyecto Laura (Peru): proyectolaura.pe

To contact the research team, please e-mail: imvaha@swisstph.ch