People are Petrified of Preservatives. Discuss.

‘Which preservative should I use to give me a three-year shelf life?’

It’s a question that I get time and time again but that I can never answer simply nor neatly. In fact, the question opens up a can of worms that, if not addressed logically and thoughtfully can end in tears.

Brand owners are right to be concerned over the long-term safety and micro stability of their creations and most of them know that using too much preservative might well lead to problems of irritation and even sensitization while too little, or using the ‘wrong’ one can lead to micro contamination which, in turn might lead to product recalls, product failure, skin irritation and even illness.  It seems like a no-win situation.  But we know that people do ‘win’ at this, that there are answers and options if only ‘we’ could unlock the know how, we too could be winners.  Let’s see what we can do….

Preserving a cosmetic product. The big picture. 

It is important to recognise straight off the bat that there is no such thing as a ‘perfect’ preservative. Indeed if there was one it would quickly become imperfect as over-using one preservative exclusively can set you up for in-house bugs, over-dosing and other such delights, best to use a mixture across a range or factory but that’s another mater….

There are lots of different options with different features and benefits that must marry up to the product you are trying to create or look for.  That said, one thing is for sure, your average cosmetic product requires a strategy to protect it from mould, yeasts and gram negative and gram positive bacteria.  We call this ‘broad spectrum’ protection and it might take more than one preservative  to achieve that.

Of course cosmetics are not all alike and nor do all cosmetics have the same vulnerabilities when it comes to choosing a preservative strategy.  Oil only products might not need a preservative at all, oil and pigment or clay products might well need something to help with mould but are less at risk from bacteria contamination (though there may still be some risk) while oil products containing salts and/ or sugars are possibly self-preserving.  On the other hand we have water containing products which, always need to be carefully looked-over for their microbial risk potential.  Sure, you might have heard of the theory that you can ‘keep the level of free water low’ but as I’m yet to find a laboratory here in Australia that can test a cosmetic for that it is a risky guessing game without testing.  Water and alcohol products might be self-preserving as might water and glycerin just as long as the alcohol and/or glycerin are at high enough concentrations.  But then again it depends on what else you put with these.  Herbal extracts,  botanically derived exfoliant particles, clays and iron oxide colours or even mica can push the micro risk up high as can the presence of sugars (honey,  aloe,  milks), proteins, peptides and amino acids.  I can totally see why people find this whole thing very confusing.  But it doesn’t have to be paralyzingly so.

The best way to find out if your product is preserved well is to test it and the first step to testing is actually getting into the lab and making it. Just do it – my first advise.

Drilling Down, Evaluating Your Product. 

The best place to start when considering a preservative for your product is to look at your formula so far with these questions in mind:

1. What is my product philosophy?  Natural, Palm Free, Organic Certified, Mass-Market, Cost-effective, Luxury etc.
2. How much can I afford to spend on my preservative input?  Preservatives can add anywhere from $0.65 per Kg to nearly $15 per Kg.
3. Is my product to be left on or rinsed off the skin?  Some preservatives are limited to rinse-off only or have stricter guidelines on the amounts that can be added in a leave-on product.
4. What packaging am I using – does the packaging make the product more or less vulnerable.  Include pack size in your thoughts too – how many times will it be squeezed, dipped into or pumped in its lifetime (estimates).
5. What pH is my final product to be?  Most preservatives have an optimal pH range to work in.
6. Do I mind if the preservative has a smell or a colour?
7. Will the preservative work with my product?
8. Can I get hold of this preservative in the pack sizes appropriate and convenient for me?
9. Is my choice of preservative legally allowed for my application/ in my country/ for my market?
10.  How vulnerable is my formula on paper?

That’s probably enough to get us started and get us most of the way to a decent preservative choice.  I’m sure I can think of more but let’s not get too crazy….

Getting those questions answered.

OK so I recognise that it will be difficult for a beginner to answer all of the above with confidence and that help might be required and that’s fine.  The best thing about the internet now is that cosmetic chemists are much more visible than they ever have been so you can always shout out for help or a second opinion on the hard bits.  But you can see from the list that some of these are questions that only the brand owner can answer and answering those is a great place to start.

For the tricky ones I’ll try to give you a bit of a head start here.

Product pH.

You can only measure the pH of a product that contains water and products that contain water go straight to the more vulnerable list so that’s significant for a start.

If yo are a product developer making water-containing products that doesn’t own a pH meter you should really get one right away as you can’t make a safe formula without one.

Knowing which pH to set your formula at is a matter for another day but when it comes to preserving your product it is fair to say that the most vulnerable pH range is around pH 5-7.  Acidic and Alkali pH’s have a slight advantage in that some bacteria don’t like the harsh conditions of an AHA type formula or a soap although that’s not to say that you can ditch the preservative altogether at lower or higher pH, more that your product just got a tad less vulnerable.

Once you have worked out what pH your product will be  you can then use that to help you select a preservative.  Preservatives are sold with pH usage ranges and as a beginner it is definitely best to just operate within those guidelines.  As you get more experienced you might be able to push your luck a bit more.

Will the preservative work with my product? How to tell. 

So this is the bit where you are wise to go into the lab and check but only after you’ve had a read of the supplier data first.  Some preservatives are rendered less active or even inactive when certain other ingredients are present.  High levels of anionic or non-ionic surfactants and zinc oxide are common trouble makers but as with any trouble makers, there are ways of making them compliant.

So once you have established that you have nothing obvious in your formula that might deactivate the preservative the only thing to do next is try it out.  There are some obvious issues that may arise when trying a preservative out for the first time.  If you are making an emulsion you might find it goes either to water or a cottage cheese consistency after adding the preservative – the main reason I advise people to add the preservative at the end even if it is heat stable is so you can observe these changes, again once you are more established you might want to add the preservative sooner or add half into the oil and half into the water which some preservative suppliers  recommend.  If you are making a spritzer or water-only type formula you will see immediately if your preservative struggles to mix in, the last thing you need there is a floating preservative!

In terms of chemistry the ideal place for your preservative to sit is at the interface between the oil and water phases. If you have no water but need a preservative then it is still important that your preservative isn’t completely fixated on the oil phase as if it is it might be so embedded in the bulk of your product that when moisture does come into contact with the formula, the preservative won’t give a damn! That said, it does make sense to choose a preservative with a large affinity for oil in an oil-dominant formula as it will need to sit and wait there.  In water-heavy formulations the same applies in reverse.  You still want your water-soluble preservative to show some interest in the oils as it is here that the microbes thrive.

Oil (food) + water (drink)  + Oxygen (fuel) = Microbe Heaven.

For beginners and long-timers alike it can be difficult to evaluate and account for all of this perfectly before hand and so micro testing or preservative efficacy testing is always recommended.  Sure a bit of prior knowledge and some careful planning will stack the odds further in your favour but there is always something there to surprise you!  The main thing to take-home is that you should try your preservative of choice in your formula and then run some freeze/thaw tests (if your product is an emulsion) just to test it out and make sure it hasn’t become less stable.  If it looks to be OK, smells OK and seems to be compatible based on the reading you’ve done then you should move on to testing.

Assessing a formulations vulnerability.

I mentioned the main culprits that increase the bio-burden (or risk factors) of a formula at the beginning of this article but to re-cap basically anything that is botanically or particulate based is likely to increase your risk when compared to a very basic product with none of those actives.  That’s a bit of a pain as many people who I deal with are looking to pack their products full of botanical extracts, natural colours, minerals and the like so I guess the main thing to keep in mind is that a risk that you know about is a risk that you can manage.

Managing the risks using other non-preservative strategies.

For very vulnerable products relying on the preservative alone is probably not going to cut it.  There are other strategies that you can use to help decrease your bioburden/ increase your chances of success and one of the most practical in most cases is to use a chelate. Chelating agents help to bind up the microbe food that your botanical and other ingredients introduce.  They don’t kill microbes directly but do help to starve them which, at the very least limits their rate of reproduction which is very useful!  Chelates are things such as EDTA (no often used in natural cosmetics),  EDDS (Good for naturals),  Sodium Phytate (Derived from basil), Sodium Gluconate and a few more. I’ve written about them before here.   Adding a chelating agent gives your preservative a big helping hand!  It goes without saying that good manufacturing practice is a winner in the well-preserved product stakes.  If you make a dirty product, your product is fighting with one hand tied behind its back from the get-go.  Hot processes where the water phase and/or final emulsion are heated to just above 72C for a snap period help to pasteurize the mixture whereas cold processes don’t get that advantage.  Other than that making sure your materials are clean before you start by storing them correctly and using them cleanly is a good idea.  Water is severely overlooked in all of this by new brand developers. Using demineralised water is highly recommended, hydrosols and rainwater are less so.  Again, it might be possible to use these things safely once you get your formula right and you are testing your products regularly but I wouldn’t start off with ‘active’ water as it could introduce more than just moonbeams and sunshine.

In other news I’d remind people who a physically stable product is going to be more micro resistant than an unstable product (relatively speaking).  This is probably where the false idea that vitamin E is a preservative comes in.  Vitamin E is a commonly used antioxidant and oxidative degradation is a common problem in natural products.  Adding a little bit of antioxidant be that vitamin E or something else can help slow down oxidative degradation and thus increase the robustness of your formula both physically and microbially.  It goes without saying though that no amount of antioxidant can prop up a formula that is physically unstable so making sure a product is physically stable before going for a preservative efficacy test is not a bad idea if budgets are tight – even doing your quick stability testing at home is a good start.

The last thing I’m going to mention here is packaging choice.  So it is pretty obvious when you think about it that a huge open-mouthed jar is going to present with more micro problems than an airless tube so if in doubt, use your packaging to help you out 🙂

Working out how much to use.

For beginners I generally advise choosing one preparatory blended preservative and using it at or around the maximum dosage. This is not an optimisation strategy by any stretch, more it is a strategy that should enable the brand owner to pass the starting point, to get a product that stands a good chance of being micro-clean all things being considered.  We can start with the optimisation work once the product concept has been proven to work.  Ingredient retailers generally give use levels, stick to them and don’t get too fancy about it.

Ok so back to chemistry – the daunting INCI names of preservatives and how to ‘sell’ them to clients.

We live in scary times apparently.  Many people steer clear of water in their cosmetics because they don’t want to have to tackle the preservative issue. I’ve lost count of how many people ask me for a preservative with a ‘nice, edible sounding’ INCI name.   The good news is that there are a few out there, the bad news is that these few may not work for you.  Sad but true.  Beyond the coconut, radish, honeysuckle and olive we have another range of inputs,  preservatives that are naturally derived but sound like chemicals.  As a chemist I do secretly wish that everyone loved chemicals like I do but they don’t and I accept that. But I accept it reluctantly because hating on ingredients just because they sound like they might be chemicals is illogical.  After all the inputs that sound like you could eat them have to, by definition (as preservatives) be pretty ‘nasty’ in order to kill things, microbes and the like.   It takes a lot of exposure time and teaching for people, brand owners, cosmetic buyers and product marketers to accept and love the ingredients they don’t automatically relate to but hopefully one day these natural-but-chemical-sounding-preservatives will gain the global acceptance they deserve.

On top of that are the ‘safe’ synthetics. I say safe like that because all preservatives have the ability to irritate as they will all mess with our natural microbes if present at high enough concentrations for long enough so what I mean here is that these aren’t parabens or formaldehyde donors, two families of preservatives that have achieved mythical villain status that no amount of chemistry knowledge seems able to breach.

So what can I say about this?  Basically I just want brand owners and the rest of you to know that the cosmetic ingredient world has moved on, got creative and can now offer a range of options from nice sounding naturals to chemical sounding naturals to semi-synthetics to fully-synethetic-but-not-terribly-nasties to help you preserve your product.  Isn’t that jolly nice!

The only other way I can think of selling a preservative system is to test it and prove that it is safe and effective, especially if you can prove that it is safe at a low dosage.  Surely the best sales pitch for an essential but not headline grabingly sexy ingredient is the results to say that it works?  I think so anyway.

So how do you test?

There are two main options that we use in the cosmetic industry, micro counts or preservative efficacy tests.  Micro counts just count (and characterise if you pay for that) the number of microbe colonies present in your product.  Cosmetics do not have to be sterile (microbe free) but they do have to be relatively clean and free from pathogens.  Microbes can be introduced into your formula via your packaging, your filling line, your manufacturing method, your ingredients or your nutrient broth of a formula.  Large manufacturers and some contract manufacturers will micro count their raw materials, packaging, bulk and filing line products as part of their quality control their process and GMP/ ISO accreditation requirements.  Smaller, hand-made, boutique product makers can’t afford to do that but they must do something – legally you must! How else will you prove that your product is safe and fit for purpose?

Preservative Efficacy Tests are also known as challenge tests and are more challenging and costly. They run for 28 days usually and your product is innoculated with microbes a number of times to see how it reacts. Hopefully it pretty much knocks out the bacteria, yeast and mould meaning that during repeat use the product will remain clean.

Preservative Efficacy Tests work best with oil-in-water emulsions and water based formulations. Oil rich formulations and waxy products such as mascara are often too compromised by the sample preparation process to gain any meaningful results from the testing and may, instead undergo repeat micro checks over their stability testing.  The best way to get an accurate and relevant result for your product is to talk to the micro testing lab who should be able to advise if their protocol will make it hard for your product to receive a fair go in the test.  An alternative protocol might be in order.

And what if I fail?

Micro testing costs money. I can’t say how much it will cost you because I have customers reading this from all over the world but here in Australia you are looking at around $150 ish for a micro count and around $700 for a PET.  At those prices you don’t want to fail.  But people think of failure as a nothing, a pointless exercise, a non-result. I look at it differently.  A failure may not be welcome but it is something. It is evidence that what you did didn’t work, evidence that you can use to make improvements next time.  A few failures teaches more than a lifetime of passes and will ultimately make you a better formulator. That said, none of us can afford to lose money so if you fail just make sure you know what you did so you can work from that.

Common reasons for failing a micro count or PET include:

• Incompatible pH
• Preservative not strong enough or quick enough acting for the formula.
• Product bio burden too high to start with either due to manufacturing method or starting ingredients.
• Preservative encapsulation into the internal phase so not available at the interface.
• Preservative knocked out by incompatible materials (see supplier data as they always list known issue ingredients, abide by that).

Contrary to popular opinion no preservative fails the micro test because its INCI name is not sexy enough.

So there is a lot to think about and people were right to be worried!

Well yes and no.  There is a lot to think about throughout the cosmetic process but people worry less about things like whether their actives will work, if they are in at the right level (right as in evidence based),  if their factory or garden shed lab is slowly becoming a microbial holiday house,  if their packaging is really helping or hindering them or if their product is really stable for as long as it should be and focus instead on preservatives.  It’s not that I think people should worry about everything, on the contrary, I think people should worry less and do more starting with learning and experimenting really.

Getting the right preservative for your cosmetic is daunting but that’s only really because the very real issue of visible mould growing on top of your creams focuses the attention.  Use that fear to your advantage to learn, plan, experiment and ask questions.

So where to from here?

If you are a cosmetic brand owner, developer or otherwise involved in this I would sit down with a pen and paper and really think about what you want to achieve here in the cosmetic market.  The skin needs moisture and moisture can only come from water so at some point in time every brand needs to think about preservatives (whether they use them or not is a different matter but a strategy must be made).  Yes there is a lot to think about but you are smart enough to think.  Sure you can make some mistakes but as long as you take the suppliers advice, ask for help if necessary and manufacture  and pack with care the odds will remain in your favour.  The one thing that I don’t advise you to do is avoid the issue, avoid preservative, avoid water-containing cosmetics because giving into fear is never smart.  Never let your fear decide your fate – it’s a motto of mine.

Please don’t be scared of preservatives, embrace this science and give a few things a try to if you need help, ask for it.

Good luck

Amanda  x