Toxic Shock Syndrome (TSS) is a rare but serious condition that raises legitimate concerns, particularly among users of internal period protection. Although its link to tampons and cups is often mentioned, menstrual TSS (mTSS) remains extremely rare.
To understand the real risk, we need to go beyond anxiety-inducing headlines and look at the biology. In this article, we analyse the mechanisms of TSS, the contradictions in current scientific studies, and the precautions you should take.
Table of contents
- 1- What is Toxic Shock Syndrome (TSS)?
- 2- Why are some people at risk? (Immunity & Prevalence)
- 3- What are the triggering factors?
- 4- Menstrual cups and TSS: The battle of the studies (Tierno vs Lina)
- 5- Wear time: Why 6 hours in France and 12 hours elsewhere?
- 6- Safety protocol: How to use your cup
1- What is Toxic Shock Syndrome (TSS)?
TSS is an acute systemic inflammatory reaction. It is not caused by the bacterium itself, but by the release of a specific toxin: TSST-1 (Toxic Shock Syndrome Toxin-1).
This toxin is produced by certain strains of the bacterium Staphylococcus aureus (Golden Staph). When it enters the bloodstream, it triggers a massive immune response leading to multi-organ dysfunction that can be life-threatening.
TSS progresses very rapidly (within a few hours to 48 hours). The first signs resemble flu or gastroenteritis, which often delays diagnosis — and these symptoms don't necessarily all appear together.
If you are wearing internal protection and experience some or all of these symptoms, remove it immediately and go to the emergency room:
- Sudden fever (> 39°C / 102°F).
- Digestive symptoms: Nausea, vomiting, diarrhoea.
- Skin symptoms: Red rash (like sunburn) on the trunk, palms or soles of the feet.
- Neurological symptoms: Confusion, disorientation, severe headaches.
- Muscle symptoms: Intense pain (severe aching).
- Drop in blood pressure: Dizziness, fainting when standing (shock state).
The role of Staphylococcus aureus is central. This bacterium is naturally present in approximately 20% of the general population (skin, nose, throat). But for menstrual TSS, everything plays out at the vaginal level.
2- Why are some people at risk?
TSS is a condition that requires the right conditions. For it to develop, a rare statistical combination of 3 cumulative factors is necessary.
| Required Condition | Frequency | Explanation |
|---|---|---|
| 1. Presence of the bacterium in the vagina | ~ 5% of women | Carrying S. aureus specifically in the vaginal microbiome (2). |
| 2. Toxin-producing capacity | ~ 4% of strains | The bacterial strain present must carry the gene capable of producing TSST-1 (3). |
| 3. Absence of immunity | ~ 15% of women | Not having naturally developed antibodies against TSST-1 (4). |
Breaking down the numbers:
The absence of immunity varies by profile: it rises to 19% among young people (13–18 years old) and among Black
women.
However, if we combine these three conditions (5% × 4% × 15%), the theoretical probability for any given woman of meeting all the conditions is
approximately 0.03% (i.e. 3 women in 10,000) (5).
For comparison: The risk of breast cancer is 120/10,000. The risk of a road accident is 57/10,000.
3- What are the triggering factors?
Having the right conditions is not enough. A trigger is needed for the bacterium to start producing the toxin. This is the blind spot of current research.
Several serious leads are suspected:
- Microbiome imbalance: A drop in lactobacilli (the "good bacteria", guardians of the vagina) leaves the field open for Staphylococcus.
- Oxygen: The introduction of air into the vagina could stimulate bacterial growth.
- Mucosal barrier: Micro-lesions (caused by a dry tampon or a difficult insertion) can facilitate the passage of the toxin into the bloodstream.
- Stagnation: Menstrual blood accumulated for too long provides an ideal breeding ground.
4- Menstrual cups and TSS: The battle of the studies
Science is not monolithic. On the subject of menstrual cups, two major studies reach opposing conclusions — and it's important to understand both to appreciate the limits of our current knowledge.
This study from New York University concluded that no TSST-1 development occurred in menstrual cups, even after 24 hours of incubation — unlike tampons (7).
Bias: The culture medium contained no lactobacilli.
The Lina study (2018): "Alarming"
The French National Reference Centre for Staphylococci (Lyon) observed the opposite: cups allowed toxin production from as early as 8 hours, potentially due to the introduction of oxygen (8).
Bias: Again, incubation was carried out without lactobacilli, which does not reflect the reality of a healthy vagina protected by its flora.
The protective role of Lactobacilli:
Recent studies (6) show that lactobacilli inhibit TSST-1 production through lactic acid and hydrogen
peroxide. Ignoring their presence in laboratory tests potentially skews results on the real danger of cups.
5- Wear time: Why 6 hours in France and 12 hours elsewhere?
There is ambiguity around recommended wear time. In France, ANSES recommends a maximum of 6 hours as a precautionary principle. In Europe, the recommendation is 8 hours. In the USA, the FDA allows up to 12 hours.
Why this difference?
French recommendations stem from the history of tampons, which caused TSS epidemics in the 1980s due to synthetic
components such as rayon. Although cups have never caused an epidemic and cases remain isolated, they are subject to the same legislative restrictions, in the
absence of absolute counter-evidence.
6- Safety protocol: How to use your cup
Even though the statistical risk is minimal (0.03% theoretical conditions), the precautionary principle applies.
| ✅ What to do | Why? |
|---|---|
| Wash your hands before and after each handling. | To avoid transferring Staphylococcus from your skin to your vagina. |
| Respect the 6-hour maximum rule. | To limit blood stagnation and bacterial proliferation. |
| Choose the right cup size. | To minimise the amount of air (oxygen) present in the vagina, which promotes bacterial growth. |
| Avoid standard soap. | S. aureus thrives in neutral environments. Use a pH-acid cleanser like La Mousse. |
| Sterilise your menstrual cup between cycles. | To kill any bacteria that may be present on the surface of your cup. |
