Methylisothiazolinone – let’s not turn it into a scare story


Although it is a long way from being my most popular post, the one I get most comments on is my one on Methylisothiazolinone and Methylchloroisothiazolinone free products.  These preservatives are used in a lot of products.  I doubt that anybody alive hasn’t come into contact with them.   Most people don’t have any issue with them, but a small proportion of people are allergic to one or other or both.  So if you sell large numbers of units, inevitably this leads to complaints.

Actually this is not remotely limited to the thiazolinones, or MI and MCI as they seem to be called now that they are getting attention in the main stream media.  Anyone can develop an allergy to anything at anytime, but preservatives as a class do seem to provoke more skin reactions than other cosmetic ingredients.

The blend of MI and MCI has been around since the late seventies and was first promoted under the trade name Kathon CG.  It was in the right place at the right time because people were phasing out formaldehyde, and Kathon was a great replacement for it.  It has none of the toxicity issues, isn’t a suspected carcinogen and it is much easier to handle.  It is also very effective at astonishingly low concentrations.  It all sounded too good to be true, and after some experience the downside began to become apparent.  As it became used more widely it began to become apparent that it provoked allergic reactions.  The quantity of reactions wasn’t extremely high, but nonetheless it was a drawback.

I’d love to portray cosmetic chemists as calm and rational experts who weigh the data with the cool logic of Mr Spock from Star Trek.   But the reality is when you get reports of skin reactions turning up in your inbox it is far from a pleasant experience.  Okay, it isn’t as bad as for the person who has had the reaction but it is still quite alarming reading about how your product has affected people.  If you read the many comments on my MI/MCI free products post you’ll find some descriptions of the symptoms.  That will give you the idea of the kind of thing that will end up on the desk of the technical manager of any company that sells a lot of products preserved with MI/MCI.

As a result formulators will, quite naturally, try and find the preservatives that elicit the fewest skin reactions.   This is the reason you see so many products preserved with parabens and MI/MCI.  Experience has taught us that these are the options that give the fewest problems.  But you are always open to any suggestion that offers hope you can get the number of adverse reports down.

And recently it looked like there might well be an opportunity.  For years MI/MCI has been supplied to cosmetic companies in the form of a blend of the two preservatives.  This was so well established that EU regulations actually only approved the blend and not the individual ingredients of the blend.  So you had to use them together.   The great thing about the blend was that it worked tremendously well at extremely low levels.  Typically 0.0008% of MCI and 0.0003% did the job.  (I think the permitted level is a touch higher than that.)

But it did mean two unpronounceable and almost unspellable names on the ingredient list.  Could we get away with just one?  The data indicated that the MI was the least irritating so switching to that ought to be a good move.  This needed a change to the cosmetic regulations.  It also meant that a new use level had to be established. As is often the case, a blend works better than a single component.  So the total amount of preservative you need for a single one is higher than for the blend.   The regulations set the maximum at 0.01% in 2005.

So it all looked good.  You cut down the length of your ingredient list, reduced the number of allergic reactions at the same time.  And now it was legal.  It took a while for the preservative suppliers to start offering the new option, and reformulation took a while, but products with MI alone started to appear.

But it does look like the change has had an effect completely the opposite of what was expected and what was intended.  Dermatologists are now seeing an increase in the proportion of their patients that react to MI.  In a paper published in the current edition of Contact Dermatology a clinic in New York reports that the number of sensitivities to MI that they are seeing has risen from from 1.94% in 2009 to 6.02% in 2012.

It is important to remember that dermatologists’ patients are not a big crowd.  There are only around 200 dermatologists in the whole of the UK, so to end up getting referred to one you need to have pretty bad skin.  Even among this unfortunate group of people over 90% don’t have a problem with this ingredient.  But even so, they are still people and if switching to MI alone formulations instead of MI/MCI ones is giving them a problem we should take that into account.

Published data like this is really useful, but it isn’t the whole story.  Companies that make the products will be keeping a careful note of the number of reactions they get.  If the switch to MI alone doesn’t live up to its promise of reducing skin reactions and actually increases them they will switch back.  Just for completeness, I should add that I personally don’t have any information about this particular preservative.  It is possible that the MI versus MCI/MI thing is a red herring and the actual reason for the increase is some other factor.  But although I keep an open mind if new evidence comes to light it looks a lot like the problem is the higher usage level of MI.

So some people have tried an idea that looked like it might help, but will have to backtrack in the light of experience.  This doesn’t sound too reprehensible to me, and it certainly was done for good motives.

So how does the public service broadcaster the BBC’s Watchdog programme broadcast on the 18th of September report it?  I am afraid I am not a regular watcher of this long running show, but I did sort of have the idea that it was supposed to support the consumer.  Naively I had hoped we would get a balanced report.

First we got an example of someone who had suffered a severe allergic reaction.  This was unfortunate for the person who had had it, and you obviously feel sympathy for them.  But people have always had allergic reactions.  This particular one was apparently triggered off by Piz Buin sunscreen, which contains MI on its own.  We met a few other people who were being patch tested, and some people were shown to be allergic to MI. None of this would be remotely surprising to anybody.

We then heard from Ian White, a dermatologist whose speciality is contact dermatitis.  He is certainly an authority – among other things he edits the journal from which I took those figures earlier.  He quoted slightly higher figures from his own patch testing of his patients.  He is finding 10%.  He then offered the opinion that this was an unprecedented rise and constituted an epidemic.  Well, no doubt he is passionate about his patients which is probably why he has such a good reputation.

But somebody really should have pointed out that he was talking about people with skin conditions, not the general public.  As I have already said, their patients really are a very small and very unrepresentative group.  This doesn’t mean they should be ignored – they are still human.  But we can’t extrapolate their experience to everyone else.

As I say, the BBC is supposed to serve the  public, and I think the public was very ill served by this article.  Some people commenting on Twitter, quite understandably given the tone and the way it was presented, concluded that they should start avoiding products containing MI.  In fact, if you are not allergic to MI now the chances of you developing an allergy to it are not high.   There are plenty of materials around that are more likely to cause an allergy.  MI isn’t even in the top ten.

The fact is that the only way to stop allergic reactions to cosmetics is to stop people buying them at all.  There is always going to be somebody somewhere who is allergic to whatever is used.  The industry has a vested interest in minimising the numbers of reactions and generally does a pretty good job.  Hopefully as we learn more we can do even better.  This particular story already has some lessons, one of which is that the mass media is not very helpful.  If MI becomes demonised like the parabens have been we will simply lose another preservative option.  What people with sensitive skin really need is as much choice as possible.  Scare stories about individual ingredients don’t help that at all.


Risk factors associated with methylisothiazolinone contact sensitization Wolfgang Uter,Johannes Geier,Andrea Bauer, Axel Schnuch Contact Dermatitis Volume 69, Issue 4, pages 231–238, October 2013

18 thoughts on “Methylisothiazolinone – let’s not turn it into a scare story”

  1. Zacharia Pankhurst

    Hi Colin,
    Apologies for cross-posting but this seemed like a more relevant post, have you seen the EU’s committee on Consumer Safety’s “Revision of the opinion on methylisothiazolinone (27 March 2014)”?

    Current clinical data indicate that 100 ppm MI in cosmetic products is not
    safe for the consumer.
    For leave-on cosmetic products (including ‘wet wipes’), no safe
    concentrations of MI for induction of contact allergy or elicitation have been
    adequately demonstrated.
    For rinse-off cosmetic products, a concentration of 15 ppm (0.0015%) MI is
    considered safe for the consumer from the view of induction of contact
    allergy. However, no information is available on elicitation.”

  2. Hi Colin,
    As a doctor who was diagnosed with an MIT allergy, I can tell you that the journey was hell. I had severe total body reactions and underwent six months of testing to figure it out. Two dermatologists did not recognize or even mention MIT. So if it takes scare tactics to make doctors and the public aware that this may be the culprit, so be it. I do understand your points about alternatives but unless the public is made aware of potential hazards, companies will not put money into research for safer alternatives.

  3. Hi Colin

    I have just been diagnosed with an allergy to Kathon, MI or whatever you like. I am a self employed beauty therapist and have had to endure 6 months of utter hell on earth, with burning hands at night and blistered skin on my face, neck and wrists, before being diagnosed today.

    I now have to contemplate either changing career, or change my beauty products I use in my salon. After an outlay of £6.5k only in January, this is going to cripple my new business. I have lost clients who have seen the state of my hands and face and have lost confidence in my products, fearing they too will react like me.

    My dermatologist informed me that Kathon has just been added to their testing strips, and that it is relatively new but already causing problems.

    A safer alternative HAS GOT to be found. I feel like a lab rat being tested on with this muck, and if my reactions are anything to go by, this ingredient has got to be banned.

    1. Hello Sarah,

      Thanks for sharing your story. I hadn’t thought of the implications for a beauty therapist buying a load of stock to which they develop an allergy before. I am afraid your dermatologist is not very quick off the mark, as Kathon has been around since the seventies. I appreciate why you are angry, but it really isn’t a question of finding a safer alternative. All preservatives cause some number of skin reactions, even the really safe ones like the parabens. Despite what you might think from media coverage, MI does not cause an unusually high number of reactions if the use level is appropriate. If MI were to be banned it would simply reduce the number of options available still further and ultimately cause more reactions, even if it might make your life easier. I remain convinced that the answer is clearer labelling. (If you don’t mind I’ll use your story in a future edition of my sensitive skin newsletter – obviously I won’t use your name.)

  4. You say only people with troublesome skin are attend a dermatologist and they will be more likely to get an allergy. I had great skin but all of a sudden it flared up with this terrible rash only then was I referred to a dermatologist who did allergy tests and the culprit was Methylisothiazolinone.

  5. i am a hairdresser and have had severe allergic reactions for about 8 yrs. after many dermatologists & allergy Drs continued to just give me prednisone I finally was diagnosed with an MI allergy. I had lived on prescription drugs, many expensive Dr visits, and time off work, not to mention being absolutely miserable with cracked, bleeding hands, swelling/ itching of the face & neck! I am now finally able to have a solution- although it is a shame companies are allowed to put such harsh chemicals into products! I was not even able to use baby wipes when my children were little because of the pain it would cause my skin! ridiculous! amy

  6. @amy – what solution have you found please?

    I am mid MI/MIT allergy diagnosis hell having redecorated my home. Its exhausting!!

  7. Daniella I have just learned to read labels and avoid all MI. I have had to change all soaps, lotions and cleaning products… here are just a few I found safe! All free & clear laundry soap, palmolive pure & clear dish soap, for my skin ONLY cetaphil cleanser and moisturizers, lotions, cetaphil makes a purse size hand wipe that I keep in my purse for public restrooms too because almost All liquid hand soaps have MI in them! I also have an allergy to PPD in all permanent haircolor so since I avoid this now I can live pain and itch free with no prescriptions needed!!!!!!!!!!!! hard to avoid these chemicals but so much relief now!

  8. I became sensitized in 2013. This is hell! It is in everything! Why is there only one affordable dish soap on the market without it? It took me 6 hours of internet searching to find it!Why do I have to keep a mini bottle of hand soap in my bag? Because I am terrified of using anyone’s hand soap in fear of reacting! My hands crack, bleed, blister, burn and discolor! When my hands react my entire body feels flu like. Please take this poison out of our products! Nothing makes me more angry than shopping in the baby section looking at all the baby products that say they are safe….. but full of MIT! READ YOUR LABELS PEOPLE!

  9. I have just been diagnosed with this allergy after 16 months of cracked,burning ,stinging itching hands. I could have cracked up mentally.Im a hairdresser and have loads of shampoos that I was using believing because they were paraben and sulphate free were ok. Most evenings I have to sit with my hands wrapped in ice packs to helps the pain.I often spend most of the night getting up and down to get fresh ice packs .This is exhausting. I have now started to use “Product Name Edited out by Colin” shampoo and conditioner and all seems to be improving slightly . Luckily for me I started to sell “Product Name Edited out by Colin” and make up so I have never had the allergy spred to my face or body .. check out the website “Product Name Edited out by Colin” . the products cannot be bought in shops and they have 0.03 natural plant preservative . they also have a 3o day money back guarantee. ive ditched all the doctors steroid creams and im using the “Product Name Edited out by Colin” .I only use a tiny bit as a little goes a long way.i will try anything to get my hands back to normal .I have seen an improvement already after 3 days .

    1. I’d normally simply delete Michelle’s post as it is promoting a product about which I know nothing. But it does raise one point about topical steroids. It is worth bearing in mind that the kinds of steroids that get prescribed for this kind of condition are generally really really mild and don’t pose any kind of health risk. Switching to an alternative product that doesn’t have a proper drug license is rarely going to be a good idea.

  10. I also have the isothiazolinone allergy, and that’s what started me looking into the effects of this chemical.

    It’s not just a potent allergen, it’s also apparently has neurologic effects in an in vivo model:

    Neuroscience. 2012 Mar 15;205:194-204. doi: 10.1016/j.neuroscience.2011.12.052. Epub 2012 Jan 4.
    Abnormal visual processing and increased seizure susceptibility result from developmental exposure to the biocide methylisothiazolinone.
    Spawn A1, Aizenman CD.

    All companies out there that use isothiazolinones: you are now on notice of the potential neurological effects. What if this family of chemicals is eventually implicated in the development of autism, for example? At what point does the potential liability for companies encourage them to find safer alternatives? The fact that there are SOME shampoos (but not many) and laundry detergents (only a few) out there means that SOME companies have thankfully come to a different cost/benefit conclusion.

    1. Thanks for that Suzanne, I had missed that paper. There is another one which is similar from 2006, so this isn’t a new concern. I am not sure why you pick out autism as a possible effect. But the more general point is everyone needs to keep an open mind and be prepared to change it as new information cones to light. I may well do a blog post on thus as you raise some interesting issues, and nobody reads this far down the comments section.

      1. Yes -we do read this far down on your blog when you stay on top of current regulations , scientific opinions, patch test dermatological evidences and journal publications as well as daily relorts of severe ongoing MI MIT reactions by consumer groups- your blog loses readership when you abandon the issue that is quite alive and active as an ongoing situation deserving ongoing updated information- and in case you may still wonder ; yes- we do read all the comments. .some of us are paying very very close attention.

        1. Thanks for that advice Rebekah. I’m afraid I don’t have the time to work on this issue full time. It is in any case an issue that is by its nature one that only interests a very small number of people even if those people are very interested. I’d certainly like to do more on it, but I have to earn a living unfortunately.

    1. Very few hard soaps use MI at all. Soap is self preserving so the only reason you would need to use MI would be to preserve something like say a natural extract during processing.

      1. Craft stores that sell soapmaking bar soap kits are including MI in the base ingredients of the kits. Its making its way in to some laundry Powders now also.

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