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Creating safe, natural cosmetics: If the microbes don’t get you then oxidation will.

April 15, 2015

I’ve been thinking about these things a lot lately,  ‘these things’ being oxidation and adequate preservation and how they come together to ensure your product is ‘safe’ or at least as safe as you can possibly make it.  You see both of these things are critical to take into account before a product goes to market and in my opinion neglecting one or both of these things will make your product more unsafe than using synthetic or ethoxylated ingredients (in appropriate ways of course) even will.  But it seems like many people choose to stick their fingers in their ears, cover their eyes with their elbow and sing ‘I can’t hear you’ rather than do something about it.

Well not us guys, not us.

In this post I really want to focus on oxidation because it is an issue that is close to my heart right now Why? Because as well as researching the heart out of essential oils and their stability right now (both practically and theoretically) I’m also having to trouble shoot and hopefully fix the stability of a handful of client formulations containing a myriad of  natural actives and extracts, all of which have a tendency towards letting go of their electrons.But before I get stuck in to sharing my thoughts on my immediate problem I’ll walk you through oxidation. and before we do that I’ll preface this by saying that contrary to the fact that I’m a ‘Cosmetic CHEMIST’ it is unusual for me to do much chemistry.  Cosmetic Chemistry mostly involves placing stuff together in a beaker and then a package so that it feels and looks nice and plays friendly with its neighbouring ingredients without changing too much.  So really we should be cosmetic physicists as we are mostly doing that.

But anyway….. Oxidation – this is a word to describe a situation when a molecule (let’s say a vitamin C for example) gets all excited and loses grip on its electron in a similar way to how you might lose your grip on your drink after getting excited and letting rip at the disco (I’m almost 100% sure nobody says disco any more).   Dropping your drink in a crowded disco is likely to provoke a reaction (maybe even a bad one) and the same could be true of the vitamin C sans electron.   The electron can then be referred to as a ‘free radical’ – a spirited ball of energy looking for trouble.  Not sure you could say the same about your spilt drink unless of course you count its potential to inflict damage through being a slip hazard.

It’s OK, I’ll end it here. It doesn’t really matter if you can or can’t visualise molecules, electrons and free radicals but it is important to realise that they exist, these tiny balls of potential chaos. The chaos that oxidation can cause depends on a number of factors but the most common types of chaos are:

  • Colour change
  • Aroma change
  • Reduction in efficacy of actives
  • Increase in irritation potential
  • Possible increased bulk formula instability.

Looking at that list really does say it all.  If you don’t properly stabilise your formula against oxidation your product can be useless in terms of efficacy, be more irritating than you designed it to be and look and smell different.  Not quite the experience you were after hey? So what kick starts oxidation?

  • Oxygen (of course)
  • Light
  • Heat
  • Humidity or moisture
  • pH conditions that sit outside of the antioxidants comfort zone or zones.
  • Formula incompatibilities.

Again looking at this list we start to see red flags popping up all over the place, red flags that we need to be aware of and take action to prevent and we can:

  1. We can manufacture in a vacuum cream mixer if we have the luxury (many manufacturing plants have these now but you won’t be able to access one for home use probably).
  2. We can choose airless packaging for our creations.
  3. We can label the mixture as ‘store between 4-20C’ or ‘keep out of direct sunlight’ or whatever else to avoid heat.
  4. We can buffer the pH to a level that is protective (as long as that is also skin and product compatible).
  5. We can avoid light, especially sunlight by using UV coated or coloured packaging and/or by adding UV filters to the mix.

And that’s as far as the average person would go as beyond that you do need to spend some money on testing and you also need to know what you are testing for and how to measure it. Investigating formula incompatibilities is easy on one level – data does exist on places like google scholar or Deep Dyvve so you can rule out the big issues with a bit of desk work but not all.

Cosmetic formulations can be surprisingly complex and these days it isn’t unusual for people to pile 5-10 actives in a formula (3 used to be heaps).  While that sounds lovely from a marketing or client perspective it is a headache for the investigative scientist trying to pin down the trouble-making active.  But that’s what has to be done.  A relatively simple way of isolating the trouble maker is to run stability testing on the base, the actives separately, the actives in a carrier (water or oil depending on your formula) and then back in the formula again either one or two at a time.  If you have stability testing ovens and the time and money to make the ten or twenty samples needed this would be great and very interesting but people often don’t.  What is most often done is that we heap in more antioxidant – ingredients that mop up the free radicals and stop the reaction -rather like the cleaner coming in a wiping up that drink you spilled at the disco…..

Antioxidants take the many forms – BHA, BHT,  Vitamin E, Rosemary Extract, Olive Extract, Vitamin C and so on and so forth.  So yes, as well as many of these being good for our skin (where they help mop up the ageing free-radicals) they can also help prevent the ingredients oxidising. But do they work? Well yes, but it’s not that simple.

We have left one important thing off our list of things that promotes oxidation and that’s humidity (or moisture).  What is the average cream, serum or cleanser if not a pack of oily and watery humidity?

Oh bum.

The more I observe the ageing process of creams, serums and cleansers through stability testing the more I’m convinced that the water within our formula is our biggest oxidative safety killer.  While that may be pretty obvious on one level, on another it’s not and is far less discussed.  I’ve observed that formulations containing high levels of free water seem to oxidise faster and more fully than those with less free water. By free water I mean water that is just swishing around in the formula rather than being tied up in an emulsion, by a thickener or bound inside a humectant.  Typically these formulations are either the water based serums with a small oil phase or surfactant based cleansers that contain essential oils and maybe small amounts of other oils.  Fully emulsified creams with a decent sized oil phase tend to fair better – I’m wondering if the lower level of free-water present in the average cream plays a part there?  Essential oil based spritzers also seem visually to be less prone to oxidation in terms of colour change or smell from what I’ve observed in stability testing although I feel that proper testing would show up more – maybe it’s less visible due to the small amount of oxidisable material available to react.  Too small to notice physically?  The possibility that blended essential oils protect each other?  The absence of fatty material to catalyse a reaction?

Who knows.

I’d dearly love to spend more time in the lab investigating this  sort of thing fully and properly rather than me just picking up observations from here and there as I go about my paid consulting work but getting the time and money together at the same time is always an issue.  That said I’m keeping my ears peeled for  research opportunities (and funding) so that I can get stuck in so if you hear of any opportunities do let me know!

So what’s next?

One thing I know for sure is that a safe product is oxidatively stable (shelf-life wise anyway).   Oxidation of actives (including but not limited to vitamins and essential oils) increases the irritation potential of the formula.  Vegetable oils release oleic acid and become more smelly AND increasingly able to penetrate deeper into the skin.  Essential oils can morph into more irritating bi-products and anti-ageing vitamins turn into lame ducks.  Not much fun and we, as formulators and product promoters need to take this into consideration (and yes, I know we do already but I’m not sure I’ve always done enough?).

I, for one will be taking much more care in specifying how these high-risk products are  manufactured, packed and stored and will encourage a ‘use it or lose it’ attitude towards consumer packed goods  but I will also be thinking more deeply about prevention and more specifically about how to formulate around these problems.  In my experience just adding a drop or two of Vitamin E (natural) or Rosemary doesn’t cut it in a high risk formula, especially these days when everyone wants formulations containing a thousand different herbs, speciality vegetable and essential oils and also because many brand owners frown on  BHA/ BHT antioxidants (not natural).  Chelating agents do help but again many brands want to avoid EDTA – the cheapest and most effective of this class – which means we have to push more natural options to their limits.  Problems, problems…..

The risks in not quenching product oxidation for the duration of its shelf life (including once the pack is opened and product use commences) may not amount to that much on the surface – a bit more irritating, a bit less smelly, a lot less active, a bit less stable – but these things add up and being a person with very sensitive skin (always has been, it’s in my genes)  might be being placed at a higher level of risk of developing sensitivities by using oxidatively unstable products so I’m going to do what I can to solve this thing or at least get a better understanding of it so that I can more accurately assess the risks involved.

I love a challenge and this is a big one.

Your thoughts and feedback would be much appreciated.

My first port of call research wise is the food industry as they look to have the best data on this sort of thing. Amanda x

6 Comments leave one →
  1. April 16, 2015 2:07 am

    Excellent, excellent post. You are spot on about just piling anti-oxidants in without specific testing. Who has time and/or money for that?

    I’ve usually gotten good natural anti-oxidant/chelating results (from a general product stability point of view) with Itaconix DSP 2K and the various phytates/phytic acid products. Aside from the Vitamin E and Rosemary Extract, do you have any other suggestions?

    • RealizeBeautyEd permalink*
      April 16, 2015 8:57 pm

      Thanks for that. To be honest I’m not sure what will work best at the moment but am about to embark on some stability testing to find out. I feel that the trick might be to use a variety of hurdle techniques just like you would with a preservative strategy and not just rely on antioxidants. It also depends on what is going to oxidise as rosemary and vitamin E probably won’t be as much help for water based oxidative actives such as green tea extract and chlorophyl rich botanicals. I was thinking of looking at Sodium Ascorbyl Phosphate for that plus some Olive leaf but I haven’t got that far into my planning yet. I guess the trick is to choose the right sacrificial antioxidants so those things react first rather than your named actives. I’d need to do more research to see what of the above is a fast vs slow trigger. I’m guessing that is also formula dependent.

  2. sukimarmelaide permalink
    March 28, 2019 9:42 pm

    I know this is an old post, but I think its still an extremely relevant one.
    I wonder if you have any thoughts on the idea of adding your normal arsenal of antioxidants, specific to that formula, & also, your preservative system, if working with an emulsion, in addition to a chelator, ph buffers, et al, depending on what’s appropriate, along with infrastructure stabilizers, in both phases, like a HEC or polymer in one, cetyl or cetearyl alcohol & maybe myristyl myristate, in lieu of problematic stearic acid, in the oil, your two emulsifiers, maybe one hot & one cold-process & here’s my thought: then put your actives into a multi-lamellar type base, & when composing your intended liposomal contents, add an additional set of antioxidants along with your actives. For the purpose of, ideally, maintaining some level of efficacy for your actives, & also, being sort of a second tier of protection for the rest of your formula at whatever time it is usually that your liposomes are breaking & delivering their contents, partially at the time of use, partially in the jar, probably.
    All I find myself thinking about lately is the coming summer season, where I live, although it just became spring a few days back..I’m actually sure that I’m already late to the planning..I’ve been rereading all your posts on rancidity & stability testing & related subjects.
    I want to do everything different this year. I’ve had some catastrophic summers because of winter-mentality formulating.
    I hope you are well.
    Warm regards, suki

    • RealizeBeautyEd permalink*
      March 28, 2019 9:55 pm

      Hi Suki, I actually can’t follow your logic there. It is all a bit jumbled. Maybe I’m just tired but if you can reframe it I’ll have a go at answering

  3. sukimarmelaide permalink
    March 29, 2019 7:07 pm

    Sorry, often a problem for me..
    What I was trying to say was: let’s say you are making an emulsion. You’ve added one cold-process & will add one hot-process emulsifier, you’ve added either Hydroxyethylcellulose or a polymer-type gel-maker, preferably pre-neutralized, to your water phase, in order to strengthen your water phase & maybe cetyl alcohol & myristyl myristate or stearic acid to heat with your e-wax in your oil phase, to strengthen the infrastructure of your oil phase; once you’ve heated both phases & combined them, at high shear, at this point, you would allow your mix to cool, periodically stickblending, until you got to room temp. Then, you could add a multi-lamellar base to hold your this specific part of the composition, you could add an additional portion of anti-oxidants to your actives in what will be your liposomes, & then either sonically mixing or gently incorporating using another method..then, at this time, you might add your regular mix of antioxidants & also your water-soluble preservatives, possibly doing some ph tests at this point & adjusting appropriately, adding any ph buffers, chelators, & fragrance or essential oils, as needed.
    My only point being the addition of the extra portion of antioxidants to be incorporated into your that upon breaking, you might have an additional level of antioxidant insulation, to deal with any other problems that may’ve arisen since manufacture.
    I was trying to kind of continue the thoughts you were discussing above.
    Regards, suki

    • RealizeBeautyEd permalink*
      April 2, 2019 6:19 pm

      I’m still not fully following your thinking but basically where your antioxidants sit would depend on the chemistry of them, your product and its phases. Things tend to want to sit where they are most comfortable as long as you give them a bit of an opportunity to find that spot – mixing etc. Temperature of mixing can affect the stability of the product and start oxidation but often there isn’t enough heat for long enough to do that with modern mixing methods. I guess the best way to know anything is to run some tests.

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