A menstrual cup is a flexible, reusable device inserted into the vagina during menstruation to collect, rather than absorb, menstrual fluid. They are typically made from medical-grade silicone, rubber, or thermoplastic elastomers and are designed to form a seal against the vaginal wall to prevent leakage. For safe and hygienic use, manufacturers recommend that a menstrual cup be removed, emptied, and cleaned at least every 12 hours. Exceeding this 12-hour limit can lead to a range of consequences, from minor discomfort to serious health complications.
Non-Infectious Immediate Effects
Over-wearing a menstrual cup can immediately cause physical discomfort. The cup’s capacity is finite, and a heavier flow can cause it to fill completely before the 12-hour mark. When the cup is full, the vacuum seal may be compromised, leading to leakage or overflow, which signals the need for immediate removal.
Prolonged containment of menstrual blood also results in a strong odor upon removal. Menstrual blood does not inherently smell foul, but when held at body temperature and exposed to naturally occurring bacteria, decomposition begins. This process creates an unpleasant, concentrated odor, though this change is not indicative of a systemic infection.
The Risk of Toxic Shock Syndrome
The most serious, though rare, consequence of leaving any internal menstrual product in for too long is the increased risk of Toxic Shock Syndrome (TSS). TSS is a severe, rapidly progressing condition caused by toxins produced by the bacterium Staphylococcus aureus. This bacterium is naturally present in the vaginal flora of a small percentage of healthy individuals.
The presence of a menstrual cup containing stagnant menstrual fluid creates an environment that can promote the growth of these toxigenic strains of S. aureus. Menstrual fluid acts as a rich culture medium for the bacteria. The combination of trapped blood and the cup’s presence is thought to favor the production of the Toxic Shock Syndrome Toxin-1 (TSST-1).
Once produced, the TSST-1 toxin can rapidly enter the bloodstream and trigger an acute, massive immune reaction throughout the body. Symptoms of systemic TSS are sudden and severe, often resembling the flu initially, but quickly escalating. These symptoms include a high fever, a widespread rash resembling a sunburn, dangerously low blood pressure (hypotension), and confusion.
Other acute signs can include vomiting, diarrhea, and muscle pain. Because TSS progresses quickly and can lead to multi-organ failure, it requires immediate medical attention. This risk is the primary reason why strict adherence to the 12-hour removal guideline is emphasized.
Alterations to the Vaginal Environment
Beyond the risk of systemic illness, prolonged wear significantly increases the likelihood of localized vaginal infections due to changes in the delicate vaginal microbiome. The normal vaginal environment maintains a slightly acidic pH, typically between 3.8 and 4.5, which is maintained by the dominance of Lactobacilli bacteria. This acidity helps suppress the overgrowth of potentially harmful organisms.
Menstrual fluid has a more neutral pH. When it is trapped inside the cup for an extended time, it neutralizes the natural acidity of the vagina. This shift in pH creates a less favorable environment for the protective Lactobacilli and can promote an imbalance known as dysbiosis. This localized change facilitates the overgrowth of other bacteria or fungi.
The most common localized infections resulting from this imbalance are Bacterial Vaginosis (BV) and Candidiasis, commonly known as a yeast infection. BV is characterized by an overgrowth of anaerobic bacteria and often presents with a thin, grayish discharge and a distinct fishy odor. Candidiasis, a fungal overgrowth, typically causes thick, white discharge along with intense itching and burning sensation in the vulva and vagina.
Corrective Measures and Prevention
If the menstrual cup has been left in for longer than the recommended 12 hours, the first step is to remain calm and remove it immediately. After removal, the cup must be thoroughly washed with a mild, fragrance-free soap and then sterilized by boiling it in water for 5 to 10 minutes before its next use. This sterilization process is necessary to eliminate any potential bacterial film that may have developed on the silicone surface.
Users should then monitor themselves closely for any signs of infection, especially the acute, flu-like symptoms associated with TSS, or the localized symptoms of discharge and irritation.
To prevent future incidents of prolonged wear, it is highly effective to set a reminder on a phone or use a period-tracking application to alert the user at the 12-hour mark. Developing a habit of emptying the cup twice daily—for example, once in the morning and once before bed—can also help ensure the time limit is never exceeded.