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

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!