By Siouxsie Wiles 25/04/2018

A new study shows that menstrual cups and cotton tampons may not be as safe as people are being led to believe.  

Diva, Fleur, JuJu, Kiko, Lunette, Me Luna, Mooncup, My Cup, Sckoon, Tāti, Wā, Yuuki. All cutesy names for the same thing: the menstrual cup – a ‘cup’ people insert into their vagina to collect blood during their period. Once the cup is full, it’s removed, emptied, given a rinse and popped back in.

I have to admit that the very idea of a menstrual cup completely freaks me out. I blame the many hours I spent either sitting in microbiology lectures as an undergraduate or teaching students about nasty microbes as a university lecturer. Because I now know far too much about the (admittedly very rare but pretty deadly) bacterial disease toxic shock syndrome, as well as the ability of the bacteria responsible to stick to things like menstrual cups. A new study just published by researchers in France has reinforced all my fears. It’s also a bit of an eye-opener for those of us who use tampons.

Periods and Toxic Shock Syndrome 101

Before I get into what the researchers have found, a brief intro to toxic shock syndrome, otherwise known as TSS. TSS is caused by the release of special toxins by the bacteria Staphylococcus aureus and Streptococcus pyogenes. The toxins are often referred to superantigens as they have this incredible ability to directly interact with important cells of our immune system, leading to what’s called a cytokine storm.

In Staphylococcal TSS this means that a normally healthy person begins to appear confused, becomes feverish, and develops a weird rash that looks like peeling sunburn. If untreated, within days they can end up in a coma, suffer multiple organ failure and die.

In the late 1970’s a new super-tampon went on sale in the USA, able to absorb nearly 20 times its weight in blood which meant it could be worn for several days. Cue an epidemic of Staphylococcal TSS and the discovery of the link between the disease and tampon-use.* Unsurprisingly, super-absorbent tampons were taken off the market. Now every box of tampons sold comes with a warning about TSS and the instruction that tampons should be changed every 4-8 hours.

To get Staphylococcal TSS you first need to have the toxin-producing form of S. aureus present in your vagina. Then the bacteria need to have the right conditions to grow and produce the toxin. Those conditions are more likely to happen if you wear a tampon for more than 8 hours. The good news is that while studies have shown that as many as half of healthy tampon-users have S. aureus living in their vagina, only very rarely is it the toxin-producing kind. Hence why Staphylococcal TSS is very rare.

Which brings me to menstrual cups, which are marketed as a cheap, safe, and environmentally-friendly alternative to tampons. I’ve also read several articles like this one, in which people say there is no risk of TSS from using menstrual cups. Turns out that’s not true at all.

Period in a bag…

In this new study, the researchers tested a bunch of different brands of tampons and menstrual cups. They put each tampon or cup in a sterile bag and added a liquid that S. aureus likes to grow in.** Then they added some S. aureus that they know produces the toxic shock toxin (one hundred thousand colony forming units per mL, to be exact). Eight hours later the researchers measured how much the S. aureus had grown and how much toxin the bacteria had made. I’ve summarised their findings in the graph below. Basically, the higher the bar, the more bacteria, and the bigger the scary-looking toxic symbol, the more toxin produced.*** It’s worth keeping in mind that this is a lab-based study, so lots of things will be different in actual people, but I still think it’s worth paying attention to the findings.

Edited 30/4/18: some people are misunderstanding the control on this graph. I’ve explained it in more detail, along with what this study can and can’t tell us about toxic shock here.

What did they find?

On average, there were about 5-10 times more bacteria and more toxin with the menstrual cups than the tampons. But there were nearly a thousand times more bacteria and a hundred times more toxin for the worst menstrual cup compared to the best tampon.

For the tampons, there were huge differences between the brands. The worst performing tampon had a hundred times more bacteria than the best. This is probably due to what the different tampons are made of. Ironically, the worst tampons were from the brand made from 100% organic-certified cotton (because women shouldn’t be exposing their sensitive and absorptive parts to “pesticide residues, phthalates, azo-dyes and dioxins…”). Go figure.

The researchers also looked to see whether the bacteria had stuck to the tampons or cups. This isn’t important for tampons, which get thrown away after use. But it is super-important for cup-wearers. As I said earlier, the advice is to rinse after each use and sterilise at the end of a period.

To me, the most important finding of the paper is that S. aureus is able to stick to the menstrual cups. This means that a simple wipe/wash just isn’t good enough as people will just be putting a cup coated with bacteria back inside themselves. Menstrual cups should be sterilised**** after every use instead. They should probably also be emptied more frequently than is currently recommended.

So do I think this means we should ditch the menstrual cups? No. Putting aside their environmental impact, tampons are bloody expensive (pardon the pun…). So-called ‘period poverty’ is a real problem, with reports of many young people missing school because they can’t always afford sanitary products. Several fantastic initiatives have sprung up that give menstrual cups free to those who need them. What people need are more than one, and clear instructions on when and how to sterilise them.

As for me, I can afford to stick to using tampons, but I’ll definitely be ditching those made from 100% cotton.

Edited 30/4/18: For an update about all the studies actually done on menstrual cups check out my post here. If you are interested in joining a community-driven open science project to answer all the unanswered questions about menstrual cups, check out my call to arms here.


Nonfoux, et al. Impact of currently marketed tampons and menstrual cups on Staphylococcus aureus growth and TSST-1 production in vitro. Applied and Environmental Microbiology. doi: 10.1128/AEM.00351-18

*Check out this video featuring US CDC researchers talking about how they unravelled the link between TSS and high-absorbency tampons.

**Brain Heart Infusion broth, if you are curious. I’m wondering why they didn’t use human blood.

***What I don’t know is how much toxin is enough to make someone ill.

****The same way baby bottles and teats are sterilised…. Though if you want something scientifically-proven to work against S. aureus, this paper suggests using shock-waves!

0 Responses to “Menstrual cups and toxic shock: no need for panic but rinsing is not enough!”

  • I use a chlorhexadine based surgical cleanser after each rinse before re-insertion. Is this enough to keep the cup clean during use. I boil and then soak in milton sterilising tablet solution before storing away for the next time. I also have two cups that I alternate between whilst one is being sterilised using the boil and soak method.
    I have always done this, having seen the effects of TSS and post surgical infection. Bacteria scare me!

  • I don’t disagree with your premise and I do think that toxin producing Staph aureus best be avoided but can you please address the negative control in your graph. The negative control, the test tube with neither tampon or cup in it, in the experiment produced more bacterial growth than all but one cup. If you take the negative control into account, it could almost be argued that tampons limit the growth of the bacteria. Without reading anything in the formal paper but the abstract, I don’t have enough data to make that conclusion but I am disappointed that you did not address the negative control results. Negative controls are included exactly to avoid data interpretation bias.

  • “Putting aside their environmental impact,”

    WHY put aside environmental impact? Thanks for the article. I will invest in a second cup and take your advice. No more tampons, ever, for me. I am a recent cup user and I now feel so disappointed with the amount of waste that has gone to landfill as a result of my period over so many years. The tampon companies are increasing the use of plastic in their applicators and they are part of the problem of plastic in the oceans. They should be made responsible for this.

  • Interesting article, thanks. Have you heard of these new Tulip Cup menstrual cups with valves to empty them? Any thoughts on these? And not sure if I’m misunderstanding the chart, but the cups seem to be about as bad as the control with neither tampon nor cup. So is this as bad as it looks, or is it probably fine so long as they’re changed regularly and sterilised each time? Not as convenient but still perfectly doable for a day out if you rotate between them.

  • Would using Milton Sterilizating Tablets on the cup create superbugs?

  • This is a very interesting study. The study is saying bacteria grows on the objects submitted to the test, but also appears to be saying buy Tampax tampons. Siouxsie Wiles explanation of TSS is very helpful, however the bacteria involved in Toxic Shock Syndrome is already in the vagina and they react with the introduced tampon (and specifically with the RAYON in the tampon) to produce the toxin TSST-1 that does the damage. The impression given by the report is that main brand tampons are the safest bet. However, there have been hundreds (if not thousands) of TSS cases from tampons containing RAYON and no substantiated cases of TSS from cups nor all-cotton tampons. I feel that we are being lead astray.

  • The accepted term for the hygienic cleansing of medical and feeding devices is sanitation and not sterilisation because the world is not sterile.

    I don’t understand your graph. It seems like there is a lot of bacterial growth with *no* tampon or cup? Can you help me?

  • I am thinking of a few conditions that may have effected that outcome though, the main one being, when the cup was in the bag with the liquid, that’s a very high surface exposure to air, which Golden Staph needs to proliferate and produce toxins? Tampons have air trapped in the cotton and that’s known to encourage growth, but when a cup is used it’s folded, with air pushed out, inserted then opens inside you with a sort of suction seal around your cervix. So there would be much less surface area exposed to air, and no air in the silicon of course. Would that have skewed results?
    I am not sure if I am explaining what I am thinking correctly. I am no lab rat or mad scientist.
    Plus tampons have a string, cups are completely enclosed by your body, no string wicking sweat, water (if you get wet), traces of urine or fecal matter possibly and vaginal discharge up into your body and the tampon itself? Would that effect the likelihood of tss?
    I have also found that once blood is absorbed by a tampon, it seems to starts degrading immediately (probably the air or reaction to the material?) removed tampons that have been worn for a while, can be brownish and smell but blood in a cup stays dark red and has very little odour other than fresh blood smell. Of course I am sure it would degrade given sufficient time but it definitely doesn’t seem to immediately or even after six or more hours.
    Have there been any cases of tss from a cup user?

  • Thank you for the article but if you can afford tampons why would you buy them instead of buying two cups instead??! Or even better buy a reusable pad through the ‘pad for pad’ scheme and help someone who CANNOT afford female hygiene products to benefit from them AND be able to attend school at the same time. You are directly contributing to environmental waste out of choice when you have the resources to help yourself, another woman or girl AND the environment. Please reconsider this as you’re clearly an intelligent woman yourself. Thank you x

  • Correct me if I’m wrong…but doesn’t simple friction washing with soap and running water get rid of staph.? Especially on a non porous surface! Why is sterilization necessary to remove bacteria that has built up on the blood in and on the cup? I’ve done research on it (googled) and elsewhere it says soap and running water removes all bacteria! Is that not correct?