Beauty News

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

You may also like...