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Skin Biome Care

Let's start this off by acknowledging that, whether we like it or not, the human body is home to billions of tiny micro-organisms - aka, microbes.

Some people shudder at the thought - but it's important to understand that bacteria does not equal bad.

It's also not as simple as "this bacteria is bad, and that bacteria is good". Many bacteria have the potential to be harmful or helpful - depending on the context.

Each area of the body has its own unique population of microbes - distinctly different populations with their own microbiome.

The microbiome of your armpit for example, will be home to a considerably different population of microbes than the microbiome of your face. This is because the microbe population in any given area will depend on the environment - the temperature, the pH, and the food sources. So, not all bacteria can survive in/on all parts of the human body. But more than that, not all bacteria have a beneficial effect when in any given area.

For example, there are microbes that live happily in our digestive tract and cause no problems - but if they were to populate the skin on our face, we might have a problem.

Equally, some bacteria might be beneficial (aka, "symbiotic") at a certain number, but if they over-grow or over-populate the area, they could become harmful (aka, "pathogenic").

What I'm getting at here, is that when it comes to microbes, context is everything - and the environment, is crucial.

Now with that all in mind, let's talk about the skin biome.

We have a diverse population of microbes on our skin, the main characters being staphylococci (yes, staph), corynebacteria, and cutibacterium. Around 89% though, are cutibacterium acnes (AKA c.acnes) - at least, in a healthy skin biome.

Some of you may find this surprising - for a long time, c.acnes has been regarded as problematic, inflammatory, and linked to acne development. It turns out though, c.acnes is not exactly the microbial villain of the biome that we once believed it to be.

Introducing: c.acnes

C.acnes is a species of bacteria that is relatively slow-growing, anaerobic (doesn't like oxygen but can tolerate it if it has to), and consumes the oils of the skin as its primary food source - making our follicles (the areas our pores lead to) the perfect habitat for c.acnes.

The bacteria was named c.acnes after the skin disease, acne - which the bacteria has been associated with for a long time.

What we didn't know up until recently, is that everybody (yes, even you) has c.acnes ALL over and inside their skin - including people who have zero acne. Which begs the question - is c.acnes really the culprit for acne development after all?

Lets' dive deeper.

Cutibacterium is a genus of bacteria, and within that genus there are multiple different species - including cutibacterium acnes.

Within each species, there are multiple strains (subspecies) - some of which are acne-causing, and some of which are critical for skin health.

The differences between these strains are so significant, that scientists have revised the naming for a few major groups of strains, including:

1: c.acnes, subspecies: acnes (strains most associated with skin disease)

2: c.acnes, subspecies: defendens (strains most associated with skin health)

C.acnes defendens

Of all the microbes on our skin, c.acnes defendens may be the most important for the health of our skin. It can keep us looking younger for longer, it can keep our skin clear, and it is critical for skin health.

C.acnes defendens consumes the oils our skin produces, and during its metabolic process, it secretes several substances:

Propionic acid

C.acnes creates propionic acid in copious amounts - it's a fatty acid that has a plethora of benefits for the skin, including:

  • actively suppresses growth of staph aureus (including MRSA)

  • broad spectrum antimicrobial activity against e.coli and candida albicans

  • lowers skin pH (our symbiotic, "good" bacteria love the low pH of our skin, while pathogenic (disease-causing) bacteria like staph aureus, do not like low pH environments

  • serves as an antioxidant

  • inhibits tyrosinase (a key enzyme involved in pigmentation)

  • inhibits biofilm formation of staph (formation of staph biofilms can contribute to skin disease)

  • regulates cell turnover


C.acnes produces copious amounts of antioxidants which are critical to reducing oxidative stress (which contributes to ageing, inflammation, and skin cancer).


Bacteriocins are antimicrobials which can inhibit certain bacteria. Most of the bacteriocins produced by c.acnes are directed at keeping staph species controlled and preventing them from over-populating. An example is cutimycin, which keeps staph.e isolated to the skins surface where it can be beneficial, and away from the follicles where it can dysregulate the biome.

ALL of these substances support a healthy microbiome, and subsequently, a healthy skin.

But here's the thing - a lot of our skincare habits have been designed around killing microbes - primarily c.acnes, including the good kind. For a long time we've been taught that microbes or bacteria on our skin are bad, and we should get rid of them - and in the process, we may have been compromising and dysregulating our skin biomes, and doing more harm than good.

We now know that not only are some strains of c.acnes incredibly important for skin health (c.acnes defendens) - we also know that c.acnes alone is not necessarily the culprit for acne development. Interestingly, some studies have even shown that acne-prone skins actually have LESS c.acnes overall - which would make sense, now that we understand what some species of c.acnes do.

So, how can we protect our c.acnes defendens? How can we look after our skin biome, and provide our symbiotic microbes with the environment they need, to take care of our skin in return?

Embrace the natural oils of your skin

Most of us don't think of oil on our skin as being a good thing - but the oil your skin produces, provides a perfect food source and environment for our good microbes to thrive. The old adage of "oily skins age slower" may well have something to do with c.acnes having the food that it needs. Oil is vital to skin health, and to the health of our skin biome - learn to love your oil for that.

Be mindful of how you cleanse

This is a very simple yet hugely impactful way you can support the health of your skin biome. We need to be mindful of how often we cleanse*:

Cleanse twice at night if you wearing make-up and/or sunscreen, and once if you weren't.

In the morning, you do not need to use cleanser - you can simply wipe over your skin with water to freshen up, but you do not need to use surfactants on your skin.

*note, this is a general guide and may vary for some skins.

We also need to think about what we cleanse with. Gentle is best, and if your skin feels tight after cleansing - your cleanser is most likely not gentle enough. We want our cleanser to remove superficial sweat, make-up, sunscreen, debris from the day - but that's it. It should clean our skin but leave our barrier and most of our oils intact.

Be mindful of your use of antimicrobial skincare

This is not to say that you shouldn't use ingredients that are anti-microbial - but we need to weigh up the pros and cons. For example: benzoyl peroxide (BPO) can be helpful in reducing acne, but it also acts like an A bomb for our microbes. A solution is to limit use of BPO to BPO washes, rather than leave-on BPO products. That way we are limiting contact with the skin, but still able reap the benefits of the ingredient.

Another example is salicylic acid (SA) - SA is excellent in reducing acne and congestion, and reducing inflammation, but we need to be mindful of our use. One SA serum for acne? Absolutely. Two SA serums, an SA cleanser, an SA exfoliant and an SA toner, all on a daily basis? Perhaps not.

Anti-microbial ingredients still have a valuable place in skincare - but moderation is the key here.

Consider incorporating skin-biome specific products into your routine

Biojuve is an american skincare company pioneering skin biome care. Their Living Biome Essentials Duo serum contains live c.acnes defendens bacteira (around 38 million microbes per pump!). It is designed to re-populate the skin with good bacteria, and create a healthy skin biome. The rest of the line (including a cleanser, moisturiser, and Biome Support Serum) are all designed around maintaining that healthy skin biome.

The bottom line

"Do the best you can, until you know better. Then when you know better, do better" - Maya Angelou

Skin biome care is an evolving science, so we are still learning - and it will be interesting to see the ripple effect that these developments in our understanding have on the industry as a whole.

One thing is for certain though: skin health and skin biome health are inextricably linked, so we must care for both.

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