Potassium sorbate

potassium sorbate
Rowan trees were original place where potassium sorbate was identified.

Preservation is a tricky business.   All beauty products that contain a large amount of water need to be preserved and all preservatives have some kind of drawback.  Potassium sorbate has been used for a long time but has recently been very widely used in beauty products that have some kind of natural story about them. How natural is it?

Potassium sorbate is the potassium salt of sorbic acid.  Sorbic acid gets its name from the latin name for the rowan tree, and sorbic acid was first isolated from rowan berries. S0 that is a nice story.  Is the potassium sorbate in the product on your bathroom shelf produced by rosy cheeked peasants harvesting rowan berries and extracting it in their cottages?  Not really.

Both potassium sorbate and sorbic acid are used in vast quantities in the food industry.  They are related, distantly, to sugars.  In nature most sugar is burnt for energy but some gets used to make other useful bits and pieces.  For instance. the sorbic acid in rowan berries.  I assume in the berries it has some kind of preservative activity.

Guide To Cosmetic Ingredients For The Perplexed Cover

Source of Potassium Sorbate

It wouldn’t be too difficult to make potassium sorbate from sugar if you put your mind to it.  With the interest from the natural products sector I am a bit surprised nobody has done exactly that yet.  Sorbic acid is not a million miles away from citric acid in basic structure, and citric acid is made from sugar cheaply and efficiently.  But as far as a I know all the commercially available potassium sorbate comes from petrochemical sources.

A molecule of potassium sorbate from any source is identical once it is in beauty products, so it’s origin makes no difference to how useful it is in a formulation.  It works pretty well as a preservative.   In particular it is good at knocking out fungi which are the bane of the cosmetic formulator’s life.  Bacteria are less susceptible so you usually need to use another preservative as well.  You also have to watch out for interactions with other components of the formulation, so it isn’t an easy option.  It is well tolerated by most people.  There are a few people out there who get mild skin reactions to it.  But is very much dependent on the nature of the formulation, so it might well be the case that some products with it will irritate, while others don’t.

Potassium Sorbate Safety

Sorbate is a part of the body’s metabolism.  So if any gets through the skin it is dealt with quickly and easily – as you would expect given that it is widely used as a food additive.  Not only your body, but micro-organisms are quite capable of dealing with potassium sorbate.  Its potential for accumulation either in the body or in the environment is therefore pretty low.

The downside is that it isn’t all that stable in formulations either.  Personally I am fairly relaxed about that.  It breaks down slowly enough to give a pretty impressive shelf life.  I have tested a five year old cream preserved with it and it has still been fine.  But it has to be said that the parabens, which have rock solid stability, do last a lot longer.  If you find a really old cosmetic product in your cupboard you should throw it away.  If you can’t bring yourself to and are in two minds, if it has parabens listed on the ingredient list it will probably be fine.  If it has potassium sorbate, maybe not.

So there it is.  Its a safe, useful preservative for personal care and beauty products. Not as green as some people might suggest but it does the job.  Most importantly, in a world where we we have more and more people living on the same sized planet, its easy biodegradability is a great plus point and one that should commend it to consumers and cosmetic chemists alike.

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Notes on Potassium Sorbate for Chemists

It has a couple of CAS numbers: 24634-61-5  and 590-00-1.  It is approved everywhere but there are some use restrictions.  The maximum in the EU is 0.8%, but that is way more than you are ever likely to need.  The EU doesn’t have much to say about potassium sorbate.

Potassium sorbate will stand you in good stead if you get to know it.  In theory it is only effective at low pHs but can contribute to the overall microbiological quality even at higher pHs.  Remember that that it is the salt of a weak acid and so tends to have a buffering effect.  In particular watch out for it contributing to neutralisation of carbomers.

In my experience a reasonable oil level in a formulation will mean hardly any skin reactions reported.  In straight aqueous formulations you stand a very good chance of somebody somewhere complaining that it has turned their skin red.  This is so rare that you probably won’t pick it up in pre-market testing.   So I wouldn’t recommend it for use in shampoos, gels and the like.  Having said that it does depend a lot on the formulation’s particular characteristics so I don’t propose that as a hard and fast rule.

The Cosmetic Ingredient Review (CIR) for sorbic acid says that it should be safe at a level of 10% in food.   So there is a pretty wide safety margin if you use it in a cosmetic product.  The Environmental Working Group’s Skin Deep database gives it a hazard rating of 3 out of 10 for no obvious reason.  As their credibility as experts on cosmetic ingredient safety is just below that of the Smurfs,  I suggest we ignore their opinion.

Other than the Environmental Working Group who few take seriously, scaremongers have not picked up on this one yet.  Indeed it ought to appeal to people concerned about the environment.  In theory it should be possible to produce sustainable grades in the future as well.  Lets hope they become available soon.


Other Preservatives

Benzyl alchohol

DMDM Hydantoin

Methylisothiozolinone/Methylchloroisothizalinone (Kathon CG)

14 thoughts on “Potassium sorbate”

  1. What a GREAT and interesting post! I found your blog via the Moneysavingexpert forums. I’ve bookmarked your page.

    When you say “Other than the Environmental Working Group who are no longer taken seriously by serious environmental activists” – could you elaborate? (I have found the EWG an irresponsible and suspicious bunch of scaremongers myself – their ‘database’ is full of contradictory information for starters). It would make me happy to know that people who actually study these issues properly would have noticed.

    1. Here is an article from the Guardian, which is pretty much the most pro-environmental issues of all the UK daily papers which is pretty scathing of the EWG. If you skim the comments you’ll see that there are plenty of people ready to argue about the issue but none are defending the EWG. I particularly liked this line “For their own purposes – that is to say, alarmism and fear-mongering (and, possibly, fund-raising) “

  2. i just happened to find your posts, must say you have described the products very well and simplified them for me. i do see a lot of people over reacting about loads of chemicals that have been used in cosmetics. lack of knowledge makes anything sound frightening. thank you for the clarity on these ingredients.

  3. I just got done blogging about potassium sorbate. Two percent of the entire population is allergic to it. I am one of that 2%. Externally. My skin gets red like a strawberry and I become a welt. It’s painful. I wouldn’t dismiss it so lightly as you appear to do on this blog. 2% is a LOT of people.

    1. 2% is indeed a lot of people, but I don’t think that figure can possibly be the true one. I have never seen a published estimate of it, but if it was anything like that high I am sure I would have met someone with such an allergy by now. Even peanut allergy is only estimated at 0.6% by the American National Institute of Allergy and Infectious diseases. (‘http://www.niaid.nih.gov/topics/foodAllergy/understanding/Pages/quickFacts.aspx). Their website doesn’t mention potassium sorbate anywhere. But the trouble is that if you hove an allergy it affects you 100%, so you have my sympathy, but I don’t think there will ever be a cosmetic preservative that nobody anywhere is allergic to.

  4. Thank you for the article. I was trying to decide whether using potassium sorbate was safe or not, and now I think it is safe in small amounts. Concerning restrictions, nowadays, potassium sorbate is limited to 0.6% in cosmetics, at least in France.
    I also searched for articles on potassium sorbate allergy and found two studies. In the first one, potassium sorbate allergy affected nearly 4% of people allergic to cosmetics (http://www.ncbi.nlm.nih.gov/pubmed/22570031), and in the other one, it affected 0.6% of people with eczema (http://www.ncbi.nlm.nih.gov/pubmed/15218738). So it seems the figures are all over the map.

  5. Thank-you for the article! I have recently decided to make my own formulations of creams and serums and slowly I’m learning about actives ( which I hope really work), emulsifiers, and preservatives and finding so much information that it can be overwhelming, especially for someone with a non-science background.

    My goal is to have customized potions that make my skin happy and stave off the aging process as much as possible by topical applications. Of course, a priority in that goal is to do no harm and I’ve read so much conflicting information regarding preservatives that it’s hard to know what to use!!

    Please keep these articles coming. They are invaluable to those of us beginning to diy!

  6. Hello, thank you so much for a really great and informative website. I have a question re potassium sorbate and citric acid. The sites I have visited write when these two ingredients are in the same product that is when they are problematic. “When combined with ascorbic acid — also known as vitamin C or citric acid — the preservative converts to benzene, a carcinogen reported to cause leukemia, DNA damage, damage to mitochondria in cells, cell death and Attention Deficit Hyperactivity Disorder (ADHD). ” http://www.wisegeek.com/what-is-sodium-benzoate.htm. Please let me know what you think about this. Thanks again

    1. Hello Keren,

      I am afraid the article you have linked to has quite a few factual errors in it. You have reproduced one of them from it. Vitamin C is ascorbic acid but it is not also known as citric acid, that is a different chemical altogether. The author has reproduced a garbled version of a widespread story about sodium benzoate and ascorbic acid. I have already addressed this in this blog post http://colinsbeautypages.co.uk/do-sodium-benzoate-and-vitamin-c-react-to-form-carcinogenic-benzene/ but the short answer is there is nothing to worry about.

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