By Siouxsie Wiles 29/04/2018

After finding that there really have been bugger all studies done on menstrual cups and toxic shock, microbiologist Siouxsie Wiles ponders whether crowdfunding and open science might be the solution.

Last week a new lab-based study came out about menstrual cups and toxic shock syndrome, the very rare but potentially deadly result of infection with the bacterium Staphylococcus aureus. I wrote about what I think the study means here, here and here.

One thing that appalled me as I was reading around the topic is that it appears menstrual cups have hardly been studied at all. Or if they have, the findings haven’t been published. I counted 14 relevant studies on the journal article database Pubmed. There’s this new one, an older similar lab-based study, three case studies, and 9 reports of actual clinical trials. Most of the clinical trials just asked people to fill in a questionnaire after wearing their cup to rate their comfort and leakage.

As far as I can tell, there are just four papers about actual clinical trials, and only one of them specifically looked at vaginal colonisation of cup wearers by S. aureus. It was a study of 604 menstruating 14 to 16-year-olds in western Kenya (2). They found 10% of them to be carrying S. aureus in their vaginas. Two of the young women were carrying a toxin-containing S. aureus strain. The researchers also took 30 used cups to see if they had the bacterium Escherichia coli stuck to them. 13 cups did. That’s not at all surprising. Bacteria like to stick to stuff, and that can end up causing an infection.

The authors reported no instances of toxic shock syndrome in the 11 months they followed their cohort. But that’s hardly surprising. If the incidence was the same as seen in tampon-users then they would have needed more than 25,000 people in the trial to have a chance of seeing one case of toxic shock syndrome.

A dearth of actual information….

So, from all my reading around the subject it looks to me like we don’t actually know:

  1. Just how much do bacteria stick to, and grow on menstrual cups?
  2. How is this influenced by what material the cup is made of?
  3. How is this influenced by how the cup is cleaned?
  4. How is this influenced by what other microbes are present in the vagina?
  5. How should menstrual cups be cleaned?
  6. Should they be sterilised after every use?
  7. How often should they be changed?

If I have this wrong and there are a whole bunch of papers I don’t know about then feel free to let me know. But if I’m right, I think this is appalling and I want to do something about it.

Let’s crowdsource this!

I propose we explore how we can use crowdsourcing and crowdfunding to answer these, and any other questions, people have about menstrual cups. We can split those questions into studies that can be done in the lab on cups and bacteria, and studies that will need menstrual cup wearers.

I’d like us to develop a series of community open science projects, where anyone anywhere in the world can contribute, and all the findings are reported online in the open in real time. To see how such an open science project could work, check out the Open Source Malaria project which I think is a good model to emulate.

If you think this sounds awesome, then check out the different options below and log your interest. You are welcome to pick more than one option!

  • If you are a menstrual cup user who would like to be part of a clinical trial, log your interest here.
  • If you are an organisation that supplies menstrual cups and would like to donate products for us to test, log your interest here.
  • If you would donate money to support the projects, go here.
  • If you have something about menstrual cups you think we should investigate, log it here.
  • If you are a researcher interested in contributing or leading a project, log your interest here.

Watch this space!



  1. 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
  2.  Juma, et al (2017). Examining the safety of menstrual cups among rural primary school girls in western Kenya: observational studies nested in a randomised controlled feasibility study. BMJ Open. 7(4):e015429. doi: 10.1136/bmjopen-2016-015429.

0 Responses to “Menstrual cups: let’s investigate!”

  • Good on you Siouxsie….read the article on toxic shock…only case I’ve seen in 36 years in practice was a post parfumerie woman with a breast infection. Love to hear more about what you’re doing
    I’m a gynae in Greymouth

  • I am a guy. Don’t women wash/sterilise these cups after each use?
    I reckon discomfort and unhygieness may occur if they don’t wash after each use.

    So Assuming they do wash, then the possibility of the bacteria sticking is eliminated, isn’t It? So I don’t get how this is a problem?

  • Comment for Jay – the study by Siouxsie showed that simple washing techniques didn’t remove the bacteria listed above; and recommended that further knowledge is provided to woman regarding these options (e.g. the menstrual cups); it is also recommended in this article that further research into what methods are needed to remove bacteria and the occurrence of this bacteria and other problems are, because there isn’t much info at present.

  • I am a brand new cup user – this is my 2nd cycle using one and I wish I had tried it sooner. I am going to try to find out more to make sure I am following the recommended instructions, but I had thought it’s ok to sterilize the cup by boiling in water at the beginning of each cycle, and rinse it with water during the cycle. I am not sure if the ‘washes’ put out by the cup manufacturers actually sterilize, or simply ‘freshen up’ the cup and give the user the illusion of cleanliness. I wonder if using an antibacterial soap would make a difference? And is rinsing in potable water sufficient or should I still be worried about bacteria in the water? I change in a washroom at work and rinse using bottled water that I carry in my bag – is this sufficient? When I find a cup I like, should I buy 2 so I can boil at the end of each day? And is boiling the best way to sterilize? I have no science background, but these are a few of my questions, I am sure someone who has a knowledge of germs/bacteria has many more…

  • Have responded as a potential researcher. Forgot to mention that if we went global (am based in UK) we could cover more brands and more ethnicities. I’m also keen to rope in some of the charity sector, regards menstruation safety for refugee women. One more thing, I might be able to secure research time from my company, as we improve our corporate responsibility. Anyway. Enough gushing…;)

  • Hi there

    Great questions and would love to see this research happen. You should get in touch with Anna, CEO from Pledge Me. She is an amazing New Zealand women who I’m sure would love to assist in getting a crowdfunding set up. @Siouxsie do you have a university in mind to collaborate with?

  • Great idea. I’m so annoyed by all these studies popping up that want to tell us cups are bad. Well, tampons are bad, but we’re not all the freebleeding type, right.
    I responded as a user of menstrual cups and being able to provide you with a few cups, you can drop me a mail to discuss details!

  • Is there any update on the project? I wear menstrual cup myself, but I am a bit frustrated with the baseless claim that menstrual cup has no TSS risk. No proper study done means there is not enough case to both support the safety nor the usage discourage. I think last year there are still brands that claim that menstrual cup usage doesn’t pose any TSS risk. This is so ignorant.