Does the Skin Have a Microbiome? | Metagenics | Blog

By Molly Knudsen, MS, RDN
The first thought that likely comes to mind when you hear the word “microbiome” is the gut. But the human microbiome extends far beyond the intestines. The word microbiome refers to the trillions of microorganisms including bacteria, fungi, viruses, and parasites that call the human body home.1 These little critters, especially bacteria, are mostly concentrated in the small and large intestine but also inhabit the skin.1 

What is the role of the skin?
The skin is the largest organ in the body and, on average, is equal to about 20 square feet.2 The skin helps regulate body temperature and water retention. Not only does it trap or release heat to help keep you warm or cool depending on the temperature outside, the nerve endings in the skin also help you feel if a surface is too hot or cold or other sensations like pressure and pain.2

But the skin’s most apparent job is to act as a barrier. It is your first line of defense, preventing germs and the sun’s ultraviolet rays from entering the body.2 Microorganisms living on the skin protect the body from invasion of more harmful bacteria or viruses.2 The skin microbiota may also communicate with T cells, which are active players in the body’s immune response, preparing them to respond to harmful organisms the skin may encounter in the future.3

What affects the skin microbiome?
Birth method: Starting from birth, the skin’s microbiome is constantly developing. The skin microbiome of infants born vaginally acquires microorganisms from the mother’s birth canal, whereas babies born via cesarean section acquire the microorganisms primarily from their mother’s skin.4
Skin physiology: The type of microorganisms on the skin is also influenced by the skin’s physiology, which can be divided into three regions.4

1. Oily: face, chest, and back
2. Moist areas: armpits, groin, and the bends of the elbows and knees
3. Dry: inner ears, palms, and forearms

The thickness of the skin, number of hair follicles, and concentration of sweat glands determine the characteristics of these three regions.4

Demographic and lifestyle factors: 
Everything from where you live (air quality, temperature, and humidity) to clothing choices to cosmetic usage and hygienic practices to job functions can influence the skin microbiota.5 Uncontrollable factors that can affect the skin microbiome include age and sex. For example, the skin microbiome goes through major changes during puberty as increased hormone levels may increase the amount of oil the skin produces.4

Besides the obvious, how do the skin and gut microbiomes differ?
Compared to the gut, the microbiome of the skin has the greatest variability of microorganisms over time.4 Research shows skin sites with the least exposure to outside environments are the most consistent over time: the ear, nose, and groin.3

Do the gut and the skin interact?Even though the skin has its own microbiome, the gut microbiome still impacts skin health. This interaction is referred to as the gut-skin axis.1
The gut microbiome may contribute to skin homeostasis (maintaining normal skin functions) and to skin allostasis (returning the skin to normal after some type of disturbance).1 The gut may also play a role in keeping the skin free of blemishes.1 The benefits the gut exerts on the skin could be due to the gut’s role in systemic inflammation, oxidative stress, and the lipid content of tissue.1

How do you keep your skin microbiota and the gut-skin axis in check?
1. Eat a balanced diet
Research shows eating plant-based foods can be beneficial in helping keep the skin clear.6 Foods like fruits, vegetables, and whole grains contain fiber and biochemical compounds like polyphenols, which are important nutrients for health and can potentially benefit the skin.6 Some of these foods are also considered prebiotics and act as a nutrient source for the good bacteria in the gut to feed on

2. Consider adding fermented foods to your diet
Fermented foods like miso, kombucha, and kimchi are common foods that contain good bacteria and may contain probiotic cultures. These good bacteria support digestion, and research shows they may play a role in the gut-skin axis.5

3. Use gentle skin products 
The skin’s microbiome flourishes under a more acidic environment. A low pH level is a measure of acidity (0 being most acidic and a high value of 14 being most basic).7 On average, the pH of the skin’s surface is below 5.7 Topical products such as soaps, sanitizers, and moisturizes can disrupt and raise that ideal pH level of the skin. Using gentle skin products and not overdoing it on the soap can help keep the skin’s pH level where it should be. In addition, topical products containing tea polyphenols may help reduce the amount of oil produced by the skin and help support a clear complexion.8

The skin is the largest and most visible organ of the body, and keeping the skin’s microbiome and the gut’s microbiome well-nourished is important for health. These are just a few steps that you can consider adding to your daily routine to support your body’s friendly bacteria.
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References

1. Salem I et al.The gut microbiome as a major regulator of the gut-skin axis. Front. Microbiol.  2018;9:1459.
2. Newman T. Skin: how it works. Medical News Today. https://www.medicalnewstoday.com/articles/320435.php. Accessed September 23, 2019.
3. Grice EA et al. The skin microbiome. Nat Rev Microbiol. 2011; 9(4):244-253.
4. Byrd AL et al. The human skin microbiome. Nat Rev Microbiol. 2018;16:143-155.
5. Dimitriu PA et al. New insights into the intrinsic and extrinsic factors that shape the human skin microbiome. mBio. 2019;10(4): e00839-00819.
6. Clark AK et al. Edible plants and their influence on the gut microbiome and acne. Int J Mol Sci. 2017;18(5):1070. 
7. Lambers H et al. Natural skin surface pH is on average below 5, which is beneficial for its resident flora. Int J Cosmetic Sci. 2006; 28(5):359-370.
8. Saric S et al. Green tea and other tea polyphenols: effects on sebum production and acne vulgaris. Antioxidants (Basel). 2016;6(1):2. 

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