A guide to the skin microbiome

Your skin is an incredibly important organ, serving as the interface between your body and the outside world. It prevents water loss, protects against invading pathogens, maintains structure and more. It also hosts a variety of different immune cells and acts as a complex immune organ. Your skin's structure and function is absolutely essential to your general health. In our last post about skin biology, we took you through some basics about physiology and how cosmetics may interact with your skin. Something we brushed upon was the importance of the microorganisms that colonize your skin. In this blog post, that will be the focus. We’ll take you through what your skin flora is, how it impacts your skin health, how cosmetics may interact with it, and more!

Skin Microflora in a Nutshell

Microflora: bacteria and microscopic algae and fungi, especially those living in a particular site or habitat. - Collins English Dictionary

Source: Science Direct

Source: Science Direct

By now, you’ve probably heard about the importance of your gut microflora, an exploding area of research today. Your general health seems to be largely regulated by the bacteria that live within your digestive tract. For example, the presence of different bacterial species as well as the diversity of the colony seems to be very important, with low diversity being linked with poor health, chronic diseases, allergy and more. Thanks to this realization, probiotics and probiotic rich foods have seen a huge boom in popularity over the last 2 decades. With such an emphasis on gut flora, it would be easy to assume that that’s the most important flora for us, but did you know that bacteria can be found all throughout your body where they are increasingly known to play an important role in function? This includes on your skin.

Between one million and one billion microorganisms inhabit each square centimetre of your skin, including bacteria, archaea, fungi, protozoans and arthropods. At the end of the day, a small group of bacteria are what ultimately dominate your skin. Interestingly, there are many pathogenic microbes (i.e. those that ‘cause harm’) that are normal members of a healthy flora - we’re now starting to shift our perspectives on them to see there's somewhat of a ‘mutualistic-pathogen continuum’ - in essence, they’re not all bad, and sometimes important.

While the skin can be thought of as one big ecosystem, it’s made up of many habitats and microbial communities. For example, dryer areas of your skin, for example on your forearm, generally have the richest diversity of microbes, are easier spots for new microbes to penetrate, and are quite susceptible to variability depending on your environment and lifestyle. In contrast, more sebaceous environments, such as your face, have much lower diversity, dominated by Propionibacterium acnes, and is a harder area for outside microbes to penetrate. This is because the sebaceous gland activity makes the skin of your face a more hostile environment compared to dryer areas of your skin.In general, your skin can be inhabited by bacteria from your environment, although it seems to have a strong selective filter (i.e. unsuitable for most microbes to live due to the acidity, salinity, etc) that protects us from harmful invaders. As a result, normal and healthy skin in whatever skin habitat has a limited number of bacteria species.

 

Source: Human Microbiome Map

Source: Human Microbiome Map

Like I mentioned earlier, your skin is the first and largest barrier for your body; it hosts a complex ecosystem that involves both immune cells and microflora. It seems that these two groups co-evolved to the immune organ that skin is today, similar to your gut flora, working together to protect us from harmful invaders.Moreover, in humans, the maturation of our immune systems, including at the level of our skin, are dependent on microbe exposure.

Source: Journal of Drugs in Dermatology

Source: Journal of Drugs in Dermatology

Although skin microflora seems to be relatively stable, disruptions in the populations, often by environment, hygiene, cosmetics, antibiotics, etc., may disrupt that mutualistic-pathogen relationship I mentioned earlier. When this happens, the microbes can instead set in motion the production of inflammatory molecules (cytokines) by the skin, leading to a reduction of overall structure and function; this can ultimately lead to a slew of problems. For example, as function and integrity go down, more water is able to escape our body through the skin. This is a key feature in the development of skin allergy, eczema, and other skin disorders. Although genetics is definitely partially responsible for the skin flora, they can’t account for the dramatic global increase in skin allergy and eczema. Treating our skin flora better may be the key that we’ve been missing in the past few decades for healthier skin.


There’s a significant association between skin allergy and microbial composition. For example, in a recent study, Staphylococcus aureus colonization and reduced microbial diversity was seen in over 90% of individuals with eczema compared to less than 5% in unaffected individuals.


Hygiene, Cosmetics and the Skin Flora

Despite all the research on the importance of hygiene on lowering disease transmission, the effects this has on our skin microbiota are only starting to be considered. Through the widespread acceptance of the germ theory, a misconception arose that ‘all microbes=germs’, which has influenced our modern idea of hygiene, now synonymous with sterilization. The history of hygiene regulations, for example in healthcare settings, reflect this. Nearly all studies in the past, prior to the last few years, that have looked at hygiene, look at a reduction of all the bacteria on our skin as a proxy for lower disease transmission. It’s obvious that such a proxy was too broad. We’re discovering now that overwashing, especially with antibacterial soap, as well as using antibiotic creams (often used in dermatology) or even highly preserved cosmetic products, may not bode well for your skin flora. A better mode of hygiene may be working with the skin flora rather than trying to strip it all away, as we’re now learning.

Source: Trends in Microbiology

Source: Trends in Microbiology

There's an emergence and potential transfer of antibiotic resistance in the skin microorganisms. This is concerning especially in dermatology, where antibiotic ointments are extremely common. This poses serious problems with managing skin diseases in the future, for example, acne, as antibiotic resistance continues to evolve, for example in P. acnes.



There’s some really interesting research currently being done to give us an alternative to some of our cosmetic products, skin treatments, and hygiene products that we’ve become accustomed to. For example, investigations for potential microbial transplants and probiotic treatments for problem skin. In a 2017 study by Seite S et al, they applied a bacterial emollient with good (non-pathogenic) bacteria to patients with atopic dermatitis (double-blind, randomized with 60 patients with moderate atopic dermatitis). They were able to significantly normalize the skin flora and reduce the number and severity of flare-ups compared to the placebo group. Note, this type of treatment with bacteria/probiotic ointments for dermatitis has had some success during the last few years of research (i.e. replicated results). Similar research is also currently being done for a variety of other skin ailments, for example, acne, eczema, and psoriasis. In addition, with respect to preservatives and actives in our cosmetic products, new ingredient innovations are happening at a rapid pace to give us fermented, probiotic or other similar preserving and treatment alternatives that may be a better option for our skin flora. More research is obviously needed, but you can be sure that you’ll see more of these products in the beauty aisle over the next decade.

Source: Teen Vogue

Source: Teen Vogue

Cool Science Alert: Skin makes and metabolizes steroid hormones, peptide neurohormones and neurotransmitters, which may be influenced by the microbe colonies, according to a 2016 study by Denda M. According to the study, the skin can even influence whole body states and emotions! Just like the gut flora, the skin flora activities are likely to extend far past the skin as this study demonstrated. Here’s another reason to treat those tiny guys on your skin well.

And that's a wrap! If you have any questions, queries, conundrums or concerns, leave them below in the comments, on The Eco Well's Facebook page or shoot us an email!

References

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  2. Denda M. (2016) Sensing environmental factors: the emerging role of receptors in epidermal homeostasis and whole body health. Springer. 403-414

  3. Grice E and Segre J (2011) The skin microbiome. Nat Rev Microbiol. 9:244-53.

  4. Kong H and Segre J. (2012) Skin microbiome: looking back to move forward. J Invest Dermatol. 132:988-939.

  5. Lehtimaki J et al. (2017) Patterns in the skin microbiota differ in children and teenagers between rural and urban environments. Sci Rep Nature. 7:45651

  6. Ross A et al. (2017) The skin microbiome of cohabiting couples. 2(4) pii:e00043-17.

  7. Ryan-Kewley A et al (2017) Non-antibiotic isotretinoin treatment differentially controls Propionibacterium acnes on skin of acne patients. 8:1381.

  8. Seite S et al. (2017) Clinical efficacy of emollients in atopic dermatitis patients - relationship with skin microbiota modifications. Clin Cosm Derm. 10:25-33.

  9. Prescott et al (2017) The skin microbiome impact of modern environments on skin ecology, barrier, integrity and systemic immune programming. Word Allerg Org J. 10:29.

  10. Vandegrift R et al (2017) Cleanliness in context: reconciling hygiene with a modern microbial perspective. Microbiome. 5:76.

  11. Wilantho A et al (2017) Diversity of bacterial communities on the facial skin of different age-group Thai Males. PeerJ. 5:c4084.

  12. Yamazaki Y et al. (2017) Role of the microbiota in skin immunity and atopic dermatitis. Allergol. Int. 661:539-544.