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Why the ‘just in case’ preservation mindset is wrong and potentially dangerous.

January 28, 2018

One thing that I hear often said in the hobby and small brand end of town is that they pop a preservative into their product ‘just in case’ or ‘to be on the safe side’.  This is usually said in regards to sugar and salt scrubs with the prevailing logic being that these products are used in the shower and that the shower introduces water into the product and therefore it could become mouldy or contaminated.  Now while that is logical I can, from experience, expand upon that and say that if said product is left in the shower and water gets in, even a little bit (say 2-5%), the sugar scrub will soon become more of a liquid syrup than a scrub and will therefore be rendered useless.  Sugar and salt are very good at taking on moisture and turning that into a brine or syrup both of which, if saturated, are self-preserving due to them being chaotrophic.  I would not, as a rule, pop a preservative into that type of formula unless relevant testing highlighted a need.

It doesn’t just stop there,  preservatives are popped in ‘just in case’ across a range of products including anhydrous and dry formulations and while some will no doubt need a little something, just adding an ingredient like a preservative to be safe is kind of missing the point entirely.

All preservatives are irritating to the skin and some are pretty nasty when you over-dose them and can leave the skin red and inflamed, itchy or otherwise damaged.  We need to get to a point where we realise that over-dosing is often worse than under-doing it.

A Preservative Efficacy Test is a test carried out to challenge your formula. The test involves adding microbes to the product and seeing how quickly it kills them. If it performs within an agreed framework it passes, if it doesn’t it doesn’t.  This test is somewhat of a gold standard test but the standard protocol used is not great for all products, in fact this test is only really good for water based formulations and oil-in-water emulsions.  Other types of formulations will require a different testing strategy to give them a fair go, your micro test house will advise you of what is best for your product. The benefit of this is that it gives you a good idea of how well your preservative system is working, the down side is that it is quite expensive,  several hundreds of dollars.

A Micro Count is quick, easy and cheap.  This must be carried out by a micro lab – don’t try doing this at home, you are quite literally dabbling in biological warfare if you do this and I’m sure you don’t want to expose your family to a whole host of nasty pathogenic bugs.  Micro counts only give you a snap shot of what is growing at the point of testing but this test can be used in a variety of ways to get a decent look at how well your non-standard (in terms of PET) products hold up to life.

One formulation that I put out there back in December was the Honey Mask below.  Usually one would expect something that contained clay and honey to be a hot mess of microbes but I had a feeling that this would be pretty well self-preserving due to the lack of free water.  I made this and another version of this in my Thursday morning class so no gloves, hats or hair nets.  We all gave the samples a try to over the next two weeks I left my jar on my work desk in my hot office and tried the product out a couple more times.  So, by the time the product was posted for testing some three or so weeks later it had been ‘challenged’ somewhat – OK it wasn’t strictly scientific but my philosophy is ‘let’s see were we are starting from then go from there’.

The recipe is below and so are the micro results (The scrubbing is just other customers results – I sent a few things in the same parcel): 


As you can see from below I got two tests done, an overall micro count and then a specific look for pathogens. It is important to do the pathogen look as while you can have some microbes in your cosmetic, you can’t have any pathogens.  This formula showed a micro count of less than 10 colony forming units per gram which is well below the 1000 required for a clean cosmetic and more importantly there were no pathogens found.

The above recipe was designed for quick home-use, home-made fun.  While it is possible that this formula would stand up as it is to commercialisation I would wish to do a few more checks before going to market with a formula like this, just to be sure that during a prolonged pack-open time and use it would remain clean.  However, as it stands I’m happy that this formula is good enough for the purpose it was designed for.

If your formula doesn’t need an additional preservative and you use one at the maximum dose, 100% of that preservative is in excess to requirements and that might make your formula very irritating.   If you use the maximum dose and your formula only needs a half dose, you have a 50% excess. This adds up in excess material costs and skin risk.  Sure there are also risks in under-cooking it and I don’t advocate for that but all too often people don’t appreciate the issues of adding too much!   Also you could have a terrible situation where you use the maximum dose of a preservative in a product and it still fails because of another issue.  Just having a preservative present is no guarantee of a safe or effective product.

So, to summarise you need a preservative strategy for each and every product and the strategy should be based on scientific evidence rather than wishful thinking or worry, a total viable count is usually no more than $150 per product  and can be substantially less.  As well as putting your mind at rest that your product is clean, a TVC also ticks the box that you have carried out your due diligence requirements to the public AND that your product was made ‘clean’  so please, do the testing, you might even be pleasantly surprised by the results!

20 Comments leave one →
  1. lindy permalink
    January 28, 2018 6:43 pm

    thank you for this great, edifying article. I always appreciate your insights. It is interesting how compelling is the temptation to add a preservative just in case, and in fact in the bottom of your page it’s even written that it should be self preserving but a water soluble preservative can be added if selling.

    • RealizeBeautyEd permalink*
      January 28, 2018 8:15 pm

      That’s right, I had to put a disclaimer on because I hadn’t tested it when I wrote the recipe and I have to be more careful when representing another company. Basically testing first is always the best policy.

  2. Ric permalink
    January 28, 2018 9:49 pm

    I cannot DISAGREE with paragraphs 2 and 3 more.
    1. Some products you mention, including so-called anhydrous products, need preservatives. It may not be the usual type or usual level but they MUST have some form of preservation.
    2. NOT ALL preservative systems are irritating to skin. Remember it is not the ingredient that may be toxic but the dose may be. Knowledge of preservatives calls for careful dose selection and skin testing. If you do that there is no need to fear preservatives or scare readers with such claims.

    • RealizeBeautyEd permalink*
      January 28, 2018 10:16 pm

      That’s fine Ric . You can disagree all you like.

  3. January 28, 2018 11:53 pm

    Thanks for this post! I posted a while back on my blog about the dangers of overpreserving as well. ‘A dash for safety’s sake’ seems to have become the norm for some. On my way to try out your honey and clay mask now. 🙂

  4. Amanda permalink
    January 29, 2018 8:03 am

    Great article!
    Interested in your thoughts on preservation and testing strategies for dry/loose formulations with low water activity. I’ve been advised by several labs they are unable to PE test this format of product…

    • RealizeBeautyEd permalink*
      January 29, 2018 10:30 am

      Hi there,
      These types of product can form mould due to their hygroscopic nature and small water content plus they are often used for a longer time period than a moisturiser due to the small dose rate and often infrequent application so it is essential to test them. I don’t have a fully validated method developed but what I do tend to do is stress the formula out as much as possible before testing by freeze/ thaw testing followed by placing it in a humidity chamber for a few weeks. During the humidity chamber I would ‘challenge’ it a little by opening it and using a brush, sponge or finger in the product (whatever is appropriate) at least twice a week during the challenge. I then run a full micro count and characterisation to see if anything is growing. That is then compared to the ‘before’ sample. I do this because it seems logical but as it isn’t yet a validated test method (due to my lack of time to test multiple items at a time using the same protocol and then following their ‘health’ for the remaining shelf life) I can’t ‘sell’ this as a method, more discuss it as an idea. Your micro testing lab might have other / better ideas too so do discuss with them.

  5. January 29, 2018 12:05 pm

    Such a timely article! I follow some formulators that add broad spectrum preservatives to products that have no need for it. I have been doing my due diligence to make sure the science behind it makes sense. Thanks again!

    • RealizeBeautyEd permalink*
      January 29, 2018 12:52 pm

      The take-home message is test, test, test, especially for these ‘not sure’ products. Testing is all part of the formulating process and guessing where preservatives are concerned isn’t a good idea. I’ve been teaching this for years but the rise of online forums has seen a huge increase in mis-information which confuses people.

      • January 30, 2018 2:29 am

        There are particularly 2 things I was looking at: 1) Dr. Bronner’s liquid that does not have added preservative and has added water. My understanding from my research was that a pH of 10 or higher meant no need for added preservative in soap but Dr. Bronner’s is about pH 8.9. 2) Mineral makeup with no water but with some vegetable glycerine where Germall plus was added. The reasoning that vegetable glycerine is water soluble.

      • RealizeBeautyEd permalink*
        January 30, 2018 8:03 am

        There are lots of different microbes that favor lots of different conditions. There are also different influences within a formula- not just water activity but whether other additives help or hinder preservation. Then you need to consider the micro counts of material inputs- some things, like powders, may go in with a high micro count. Then we have to think about the manufacturing procedure and cleanliness, post- manufacturing steps (irradiation/ storage/ shipping), packaging, pack size and usage instructions. In short, while you can do a ball- park risk assessment on what you see in front of you, it’s only by testing that you know if you’re in the sweet spot of being preserved enough but not too much. Some soap and powdered make-up need preservatives while others don’t. Oh and don’t forget that there are materials that help preserve that aren’t strictly preservatives.

      • February 3, 2018 12:21 pm

        Thanks Amanda! Very helpful as usual.

  6. April 27, 2018 4:22 am

    Do you have any ideas as to why the counts came in so low? I’m just wondering if the clay had anything to do with it? It would be interesting if you could make a anhydrous product with honey and get the same test results…

    • RealizeBeautyEd permalink*
      April 27, 2018 10:43 am

      Hi there, It could be that the ingredients all happened to have a low micro count going into the mix or it could be that the mixture was incompatible with life for any microbes that were in there initially. I’d have to talk to a microbiologist to know for sure but after taking with the clay processor it is known that some clays do have an anti-microbial action so that could be enough to kill what’s there in a product with such a low free water content. I could be wrong though, I’d have to do a bit more looking. <10 is the lowest result they give at this particular lab with this particular method.

  7. Gis permalink
    May 19, 2018 11:54 am

    Based on my understanding, glycerin can help to prevent microbes. Could the addition of glycerin at a higher concentration help as well?

  8. Gis permalink
    May 19, 2018 11:54 am

    Based on my understanding, glycerin can help to prevent microbes. Could the addition of glycerin at a higher concentration help as well?

    • RealizeBeautyEd permalink*
      May 22, 2018 9:10 pm

      Glycerin is able to bind water and keep the overall ‘free water’ level of the formula low. This may be a good co-preserving strategy but it won’t necessarily be strong enough to rely 100% on. Also I’ve found it impossible to find a lab that can measure my free water content of an emulsion so at best all you can do is guess usually. Then there’s the fact that using glycerin can affect the emulsion stability as it makes the water phase heavy and it also can make a product sticky.

  9. Hanabi permalink
    June 24, 2018 4:52 am

    Hi , can I ask if exchanging the Brazilian clay for Moroccan rhassoul clay would be ok .
    TIA

    • RealizeBeautyEd permalink*
      June 30, 2018 9:02 pm

      You could but they are very different clays in terms of their flow and feel but I’m sure it would work

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