All About the Skin Microbiome

We’ve been clinging to anti-bacterial hand soaps, sanitizers, and cleaning supplies for the past year, and bacteria has gotten a bit of a bad rep. Bacteria has, in a way, become synonymous with illness even though not all bacteria cause sickness (also COVID specifically is transmitted via a virus not bacteria, but that’s a topic for another blog). Not all bacteria will lead to a bout of food poisoning or strep throat. In fact, there are thousands of different species of beneficial bacteria, and they’re everywhere — in your yogurt, in your gut, and...on your skin. 

What is the skin microbiome?

This collection of bacteria on top of your skin is called the skin microbiome, and you may have seen this buzzword on skin care products or skin care related media. 

So why all the sudden hype that has skin care experts and enthusiasts flocking to “microbiome friendly” or “microbiome balancing” skin care products?

Microbiome is defined as the microorganisms (bacteria, fungi, viruses, etc.)  in a particular environment. This includes the body or a part of the body such as the gut, nose, mouth, or, in this case, the skin. 

The skin microbiome, also known as the skin flora, is made up of about one thousand different species of bacteria, as well as fungi, mites, and viruses. They all take up residence on our skin, and work together with the skin barrier, the outermost layer of skin, to activate the immune system and protect the body from outside aggressors like pathogens, infection, UV rays, and pollution. 

However, not all microbiota are good tenants on our skin.

Good vs bad bacteria

The bacteria in our microbiome can be broken down into three categories: commensals, symbionts, and pathogens.

  • Commensals are bacteria that gain benefits from us, but do not provide us with any benefits in return
  • Symbionts are mutually beneficial
  • Pathogens benefit from us, but often cause disease or harm in return

A healthy skin microbiome will ensure that there aren’t any overgrowths of pathogens that can cause infections, and the symbiotic bacteria can limit inflammation and protect from environmental aggressors like pollution and UV rays.

But the goal isn’t to just get rid of all the “bad” bacteria and replace it with “good” bacteria, a healthy balance of diverse bacteria is optimal.

Why the microbiome is important

The first level of your immune system is your skin. It creates a barrier between your internal organs and pathogens, pollution, UV rays, and any other environmental stressor. Your skin draws a line of defense against the outside world, and the microbiome is on the front line. 

When pathogens — bacteria, viruses, or other microorganisms that can cause disease — invade your skin, they trigger an immune response, and the mutually beneficial symbiont bacteria help limit the overgrowth of these pathogens.

The skin microbiome also has direct effects on the appearance and texture of your skin. An off balance microbiome can result in:

  • Dry, flaky skin
  • Eczema, psoriasis, and rosacea flares
  • Premature signs of aging like fine lines and wrinkles
  • Acne

A higher concentration of the bacterium Propionibacterium acnes can result in acne, those with eczema typically have a larger population of Staphylococcus aureus, psoriasis is associated with low levels of bacterial diversity, and the mite Demodex folliculorum feeds on sebum which is plentiful for those with rosacea. These are just some of the ways that imbalances and disruptions and shifts in the microbiome can trigger adverse skin reactions.

Differing microbiomes

Everyone’s microbiome is different, and each individual’s microbiome consists of varying microbes on different parts of the body. The microbiome is adaptable, and will change to suit your individual needs.

The main factors that affect an individual’s microbiome are:

  • Skin pH - The average skin pH is slightly acidic at ~pH 5. 
  • Climate (Moisture and Temperature) 
  • Oxygen:carbon dioxide ratio
  • Sun exposure: ultraviolet radiation (UVR) damages microorganism DNA
  • Pollution 
  • Interactions with other microorganisms
  • Innate host defenses (age, gender, etc.)
  • Genetic makeup

If you live in a hot, humid climate, your skin is more susceptible to high levels of bacteria on the back, underarms, and feet. A teenage boy living in a city and a middle aged woman in a rural environment will have different microbiomes (and you can probably tell from the difference in odor and breakouts). One study found that there was a decrease in the S. aureus bacteria on subjects in alpine climates which are characterized by low levels of pollution; the amount of this bacteria has been connected to severity of eczema symptoms, and sure enough the subjects in the alpine climate showed less severe eczema symptoms after six weeks. 

Read more about how pollution affects your skin.

The diversity of the microbiome is why you can use all of the same skin care products as someone else, and still have completely different skin.

The microbiome varies on different body parts

Your individual body itself will also contain differing bacteria levels since you have a lot of skin, and it’s not all created equal. For example, your chest, back, and face house higher amounts of bacteria since they are more oily than other parts of the body. Not surprisingly, these body parts are more susceptible to clogged pores and acne. 

Other factors that can negatively affect the skin microbiome

  • Some antibiotics - While antibiotic prescriptions are common for treating acne, incorrect or overuse of some antibiotics can alter the nature of the microbiome in a negative way, and the effects may last long after treatment stops.
  • Antibacterial soaps and sanitizers - We’re all washing our hands more often and using hand sanitizer when we can’t get to a sink, but this is damaging to the skin on our hands. Antibacterial soaps and sanitizers not only kill illness causing bacteria, but also a lot of the good bacteria that maintain microbial balance and keep hands hydrated.
  • Disconnection from nature - Human evolution occurred alongside varying plants, species, environments, and other humans. These factors all impacted the microbiome and immune system, and continue to do so. As environments adapt and change, so do we, and so does our microbiome. You may have heard the concerns that children won’t have as strong of an immune system due to the pandemic keeping them inside, and, as aforementioned, skin is the primary barrier of the immune system. Exposure to the natural world from an early age is the first step of developing a wide range of skin microbiota, and a strong immune system.
  • Heavy skin care routines - If you’re boasting a ten step skin care routine, you may want to consider a more minimalist skin care routine. Too many skin care products can limit the bacterial diversity on our skin and lead to various problems like dryness, an overproduction of sebum (oil), breakouts, redness, and other inflammatory conditions like eczema or rosacea.
  • Showering - The length, frequency, and temperature of your shower can all negatively impact the microbiome. 

There’s a misconception that our skin needs to be squeaky clean in order to be healthy, but showering multiple times a day and over-cleansing can strip your skin of healthy bacteria and throw off the microbiome balance. Daily, full body showers were not always a commonplace practice, and some dermatologists suggest only washing your underarms, groin, and feet most days, and taking a longer shower less often. Some people even avoid a full blown shower altogether and don’t use soap at all, and let their microbiome do all the work to keep them clean.

Naturally, not everyone is keen on giving up their daily showers, so when you do hop in for a rinse, make sure to shower in lukewarm water, use a gentle, pH balanced, fragrance free body wash, and follow these shower tips for healthy skin.

Gut microbiome

When the topic of good and bad bacteria in the body comes up, it’s likely in relation to the gut microbiome rather than the skin. Gut health has been a huge topic of research and conversation lately, and for good reason. Our gut bacteria makes up 99% of our entire microbiome. A lot of studies point to gut health having effects on not just digestion, but also mental health and skin health. 

An imbalance in gut bacteria can lead to inflammation which can make its way to your skin. There appears to be a distinct connection between an imbalanced gut microbiome and severe acne. A healthier, more balanced gut microbiome has been shown to improve signs of acne and rosacea, and one study on individuals with acne showed that 80% of the subjects who supplemented with probiotics saw a decrease in acne. 

How to care for your skin’s microbiome

  • Healthy, balanced diet - If you eat nothing but processed junk food, your gut microbiome does not get the diversity of bacteria from the healthy whole foods that come from plants, and the bacteria cannot adequately feed themselves which can cause toxins to be released into the body, which leads to inflammation. The best diet for healthy skin is a well balanced diet that’s high in fiber, protein, leafy greens, and a wide variety of fruits, vegetables, legumes, and nuts is optimal for gut microbiome health which has an effect on the skin microbiome as well. 
  • Exercise and Sweating - Working up a sweat a few times a week is beneficial for bacteria. Some species of bacteria feed on sweat, so it acts as a prebiotic in that case. 

However, like we said before, not all bacteria are good bacteria, and particular strains of bacteria can release pungent smells which result in body odor. Not ideal. But a diverse microbiome that contains an adequate amount of good bacteria can help limit odor. So go for a jog or take a yoga class to feed a diverse spectrum of bacteria, and use an aluminum free deodorant to help ensure you do not kill off the less odorous bacteria.

  • A gentle, pH balanced skin care routine - Use a cleanser with more gentle surfactants (cleansing agents) as opposed to harsh detergents like SLS to diminish excess oil, but keep good bacteria in check. You should also avoid toners with harsh alcohol ingredients that may kill off good bacteria. 
  • Probiotics and Prebiotics - Probiotics are beneficial live bacteria that can be found in food and supplements. Prebiotics are the high fiber foods that our bodies can’t digest, so it becomes food for those probiotics living in our gut. The combination of probiotics and prebiotics ensure a healthy microbiome. Both can be naturally obtained from our diet, but they are also readily available in ingestible supplements as well as some topical products.

The microbiome is complex and diverse, and if not properly cared for, it can lead to long-lasting problems for your skin. So use these tips and try skin care that is not too abrasive or anti-bacterial to make the little helpful bacteria on your skin as happy as can be.


Acne vulgaris, probiotics and the gut-brain-skin axis - US National Library of Medicine

Impact of Antibiotics, Antiseptics on Skin Microbiomes - Penn Medicine

Skin Microbes and the Immune Response - National Institutes of Health

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