Women who use menstrual cups often do so because they produce less environmental waste, cost less and last longer than tampons or pads. However, the results of a new study out of University Claude Bernard in Lyon, France found that one trade-off of menstrual cup use is increased risk of toxic shock syndrome (TSS), a life-threatening bacterial overgrowth characterized by rash, fever, low blood pressure and in rare cases, death. The illness affects roughly one in 100,000 women in the U.S. every year. In 2016, the CDC reported just 323 cases and 26 deaths.
For the study, the researchers tested four menstrual cups and 11 types of tampons to see how they affected the growth of Staphylococcus aureus, the bacteria that produces toxic shock toxin 1 (TSST-1), the toxin behind TSS. The scientists used a "modified tampon sac" bag to create conditions similar to those found inside the vagina. This was the first study to look at menstrual cups and TSS.
The findings were unexpected, because although tampons get a bad rap for TSS, "most tampons reduced S. aureus growth and TSST-1 production, with differences based on brand and composition," the researchers wrote in the study. No such luck for menstrual cups, however. "We observed higher S. aureus growth and toxin production in menstrual cups than in tampons, potentially due to the additional air introduced to the bag by cups, with differences based on cup composition and size," they wrote. The findings were published on April 20, 2018 in the journal Applied and Environmental Microbiology,
So why would menstrual cups be more conducive to TSS than tampons? The researchers explain that the volume and shape of the average menstrual cup allows for greater aeration (air circulation), which in turn encourages growth of bacteria. They also found that S. aureus bacteria can use the cup to its advantage by creating a biofilm within, which is very difficult to clean off. Although some cup manufacturers recommend washing the cup with soap and warm water between uses, the researchers insist that sterilizing the cup in boiling water between every use is the safer option.
The tampons of today are not as absorbent as the ones that were sold when TSS first became linked with tampon use in the late 1970s. Nevertheless, users shouldn't leave a tampon in for more than eight to 12 hours -- the longer one stays in, the more likely bacteria is to grow. And both tampon and cup users should also thoroughly wash their hands with soap and water before any insertion or removal of these devices.