Cosmetic preservatives and facial bacteria

The key source of your future healthy skin bacteria? (Image by andreas160578 from Pixabay)

An interesting study published in The Journal of Cosmetic Dermatology caught my eye recently, which examined the effect on healthy facial bacteria of cosmetic preservatives. You can see an abstract summary here.

The five preservatives tested were methylisothiazolinone — or MI, a major cosmetic allergen in which I have a special interest) — ethylhexylglycerin and phenoxyethanol (both quite common in more natural-leaning cosmetics), and methylparaben (a parabens preservative, common in high-street and mainstream cosmetics, but avoided by some for unproven health concerns). The fifth was iodopropynyl butylcarbamate, which I have not come across much in British cosmetics, but may be more prevalent than I imagine.

As the job of preservatives is to kill or at least inhibit the proliferation of bad bacteria so that your cosmetics do not go ‘off’, it is hardly surprising that they tend to have a similar effect on the beneficial bacteria which make a home for themselves on your skin, and which are key for dermatological health.

The researchers found that all five preservatives “inhibited survival” of the nine facial resident bacteria isolates tested, when tested at the maximum allowed limit.

The effects of preservatives on our skin’s bacteria have been poorly researched, but to my mind this does beg a few questions:

  1. Skin bacteria balance has an impact on acne and symptoms of eczema … could the preservatives used in topical preparations (both cosmetic and medicinal) be having detrimental effects on the skin health of those using them?
  2. Should we be avoiding water-based — and hence preservative-containing — facial skin creams in favour of oil/wax-based balms instead, to get around the problem of potentially negatively impacting our skin’s healthy microbiome?
  3. Should we be researching probiotic-rich skincare? Essentially, replacing the healthy bacteria lost on our skin with fresh colonies from a jar?

I’m intrigued as to where this subject could lead us, and whether tailored solutions could be the way forward, perhaps based on research into our own personal skin microbiome, in order to indicate which preservatives we should avoid in order to reduce the impact on our good bacteria.

Or even tailored probiotic skincare, with bespoke creams inoculated with your own personalised mixture of healthy bacterial strains, ideally cultured for your own skin.

Who knows what future cosmetic science holds for us?


  1. Micki Rose

    Fascinating, thanks Alex. I have recommended oil and wax-based serum type things for years and this will make me do it more. I believe there are some probiotic-based skin products out there, have been for years, but they don’t seem to have expanded as much as other areas – presumably because you need to keep them refrigerated to keep them live? One option I’ve often given is to stir some probiotic powder into your favourite cream and make your own. That needs to be with no essential oils or herbs in that will kill the probiotics though.

    1. Alex (Post author)

      You’re welcome, Micki. Yes, there are, and we’ve had a few enter the Awards – such as Aurelia Probiotic Skincare – but there’s still the question that these creams have to be preserved, so what the effect of those preservatives are on both the skin and the probiotics in the product remains one to answer. And yes, there’s the refrigeration issue too … I like the idea of DIY probiotic powder in your own EO-free oil blend, but … which probiotics? I think that’s another issue that may need exploring. I doubt one size fits all … but you probably know more about this area than me, at least for the gut!

  2. Kal

    I love a good article backed up with a decent peer reviewed study! It confirms what we have known all along. After all, it’s common sense. Preservatives are not intelligent. Preservatives, like any chemical, can not differentiate between mammalian cells like ours, unwanted microbial cells and wanted microbial cells. ALL cells get attacked equally. So it’s imperative we use preservatives in which the method of action is fully understood, which causes the least harm, at the lowest possible concentration, to reduce risks.

    Probiotics is an even far more complex subject field. Yes, it is documented and understood a healthy microbiome is essential for health. However, what isn’t understood is what exactly constitutes as a healthy microbiome, as a healthy microbiome varies wildly from person to person and contains thousands of different species. Each person’s microbiome is as unique as your fingerprint. So slathering a probiotic containing only a few species of microbes onto your skin is at best, ill-advised and there are numerous studies to confirm this, as probiotics can actually reduce biodiversity on your skin.
    The best way forward is to use skincare that nurtures your microbiome rather than attempting to change it, either through pseudo-science or harsh chemicals.

    You can read more of our article in our blog here, with links to various studies:

    1. Alex (Post author)

      Thanks Kal. Some preservatives are more targeted and effective at dealing with certain types of bacteria / virus / mould while others have more ‘broad spectrum’ qualities so is it accurate to say that all cells get attacked equally? But I agree re: probiotics: hugely complex, so much still to learn, and uncertain benefits … though I like the idea of supporting what you’ve got! Thanks for the link – will take a look. Alex.

      1. Kal

        That is a good point Alex. You are correct in saying that some preservatives work more effectively against certain bacteria, fungi etc.

        This is down to how the preservative causes damage to the cell in order to kill it. So while not all microbes are affected the same, all cells are subjected to the same chemical disruption.

        This is mainly down to the physiological differences between gram positive/negative bacteria and yeasts / moulds. There are beneficial and harmful microbes in each category and it’s impossible to target a single strain of a harmful microbe without also harming similar beneficial microbes in the same category – this is partly why antibiotics shouldn’t be taken unless necessary.

        All of that and that’s before we even look into how our skin is affected which is really going into the unknown as there is a very complex relationship between your microbiome and the immune system itself.

      2. Julie Macken

        Hi Alex
        YES! I’m so happy people are starting to take notice of the fact that all water-containing cosmetics must contain preservatives which can upset our natural skin flora.
        We’ve been formulating skin care for 2 years now without water – advising our customers instead to get the humectant portion of their skincare either from natural Aloe Vera (from the plant not a bottle – cos these also need to be preserved!) or honey, or beeswax (our balms contain our beeswax – one of the few natural humectants)
        I’ve been convinced for a long time that this will soon become mainstream – just read the bottle -if it says ‘aqua’ it’s there for the manufacturer’s benefit not the user’s!
        thanks for posting this article, Alex – there is another one done from an Indian team I’ve recently read too (although I now can’t find it!) – which is essentially making the same conclusions

        1. Alex (Post author)

          Glad you found it interesting!

        2. Carla

          I am a bit new to formulation with water and I have my own cosmetic using just oil based ingredients for 10 years.
          I have being fascinated by the skin microbiome and possibilities to bring balance using pre and probiotic.
          However I need to disagree when you say that if the bottle contains “water” it is for the benefit of the manufacturer.
          I am formulating for a medical herbalist and in the vast majority of people looking for medical topic treatment for such cases as psoriasis, eczema, acne and rosacea a anhydrous treatment can exacerbate the condition if the skin is inflamed and hot. It is like adding more fuel to a hot pan.
          We had to introduce water in the formulas to help to cool down skin, relief inflammation and help to calm down the “fire”. In that case this is not for my benefit as I do prefer using all organic and natural ingredients.
          Formulas containing water, preservative ( even naturally derived ) and emulsifiers are much harder to make and quality control and to be honest I don’t charge as much as I should for the work I put on in these formulas so I don’t think ( as with probiotics) one size fits all: people who manufacturer with water benefit just themselves.

  3. Angela

    This is the exact question I was trying to find answers to when I was doing research about probiotics being added into dog shampoo.

    It doesn’t make a lot of sense to my scientific brain that adding probiotics in with phenoxyethenol or methylisothiazolinone wouldn’t just kill off bacteria and the benefits of having it in the shampoo.

    Great ideas!


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