The human microbiome and the skin 

Many sources now discuss the microbiome, the field that studies the genes of all the microbes living in and around the human body. It’s been estimated that between 2 and 10 times more microbes live in association with human cells than the human body actually holds cells with human DNA.

Truly, microbes are by far much smaller in size than human cells; still they make it up in number and interactions. We are starting to understand just how important those interactions are to health and immunity. 

microbiota = flora = microbial mix or composition

What is the skin microbiome?

To answer this question, first, let’s think of the skin. The skin is an organ, the biggest of the human body; it is also an ecosystem where microbes live in symbiosis on its surface.

The skin serves as a barrier to harmful environmental factors and just as in the gut, the diverse community of microbes that live on the skin plays an essential role in maintaining skin health.

The skin microbiota comprises many different microorganisms, including bacteria, fungi, yeasts, and viruses. Each type of microorganism has a specific function.

They are all a part of the dynamic ecosystem of the skin and provide different benefits, including protecting against infection, regulating inflammation, and modulating the immune system. Some bacteria help break down sweat and oils on the skin, others protect the skin from harmful viruses and fungi, and help keep the skin moist and prevent dryness. Mostly, it’s in the number and their balance that they are most impactful.

Studies found that certain balance of bacteria and fungi on the skin can help protect against the development of atopic dermatitis, also known as eczema. The microbiome might also play a role in wound healing. These findings suggest that the skin microbiome plays a significant role in maintaining skin health, preventing dysbiosis (disbalances of the microbes) and opportunistic diseases such as acne and rosacea.

Composition and diversity of the human skin microbiota

The skin microbiota is diverse and varies not only in the composition of microorganisms but also in the area of the body these microorganisms are situated. For example, the palms of the hands and soles of the feet tend to have different types of bacteria than the armpit.


The microbiome's composition varies from person to person, from site to site, and changes over time. The human skin microbiota is a complex ecosystem composed of many different microorganisms, and they constantly interact with each other and the environment.

The microbiota is influenced by various factors, including diet, hygiene, gender, age, and the use of antibiotics. It is also influenced by our lifestyle and hormonal variations, lack of sleep, or stress!

The initial skin colonization in newborns differs according to how the baby was delivered. Vaginally born babies acquire microorganisms typical for the vaginal flora, while C-section babies acquire microorganisms associated with the skin flora.

During puberty, microorganisms rearrange under the influence of changing hormones. In adults, the microbiome ecosystem keeps its composition stable for long periods of two years and more, if no other factor is changed.

Different skin sites offer different conditions for the microbiota. Sebaceous sites like the face, the back, and the chest are an excellent environment for Cutibacterium, Staphyloccocus, and Malassezium yeast. Dry skin sites like the arms and legs provide suitable conditions for Gammaproteobacterium and Betaproteobacterium. Moist sections (like spaces between toes and fingers) provide good conditions for Corynebacterium and Staphylococcus.


The microbiota varies depending on the skin site as well. Sebaceous sites have a lower diversity of bacteria, while moist and dry areas show medium to high heterogeneity.

The function of the skin microbiota

One of the most important functions of skin microorganisms is to protect the skin from colonization by pathogenic microbes. The skin harbors a large and diverse population of microorganisms that compete for limited nutrients, and they have adapted to survive by utilizing the sparse nutrients available on the skin.

Microorganisms adapt to the harsh conditions on the skin by forming biofilms. Biofilms are communities of microorganisms held together by an extracellular matrix that they produce, and this matrix protects them from desiccation, antibiotics, and other hostile conditions.

The formation of biofilms is why it is so difficult to treat skin infections. The bacteria in biofilms are much more resistant to antibiotics than bacteria that are not in biofilms.

Another way that microorganisms have adapted to survive on the skin is by forming symbiotic relationships with other organisms. Many species of microorganisms live in close association with humans and other animals. These microorganisms benefit from the nutrients and shelter provided by their hosts, and in return, they help protect their hosts from pathogens.

What affects the skin microbiome?

When the skin microbiome is out of balance, it can lead to skin problems such as acne, eczema, and atopic dermatitis (AD). A healthy skin microbiome is essential for keeping the skin looking and feeling its best.

Here are a few things that can disrupt the balance of the skin microbiome.


Exposure to environmental pollution can lead to many undesired changes in the skin condition, such as sebum secretion rate, inflammation markers, pH, lipid, collagen, and elastin levels.

The use of chemicals on the skin

The use of harsh chemicals on the skin, such as sulfates, triclosan, and parabens, can lead to changes in the balance of the skin microbiota. These chemicals are often found in mass cosmetics and can kill both good and bad skin bacteria, leading to an imbalance in the microbiome and causing successive skin problems.


Over-washing (and using too much hand sanitizer) can also hurt the skin microbiome. It can remove the good bacteria that protect the skin from harmful microbes and strip the skin of its natural oils. Washing the skin regularly is beneficial, but it is also important not to overdo it. To provide adequate care, use cleansing products that give a good cleansing but keep the skin's microbiota intact.

To maintain a healthy skin microbiota, use natural cleansers at neutral pH that won't strip away all the beneficial bacteria, avoid over-washing, and use quality moisturizers. Aim to wash your face no more than twice a day. We recommend once a day, in the evening, to ensure the contaminants of the day, as well as sunscreen or makeup, are removed, while not overdoing it in the morning.

For the hands, which can represent a vector for the transmission of diseases - we have clearly felt this in recent years - it remains important to clean regularly. The strategy will then be to restore the oils and other compounds essential to the skin of the hands, using a good hand cream.


The use of antibiotics can also harm the skin microbiome, increase drug resistance, and grow antibiotic-resistant pathogens. Antibiotics kill both good and bad bacteria, which can lead to an imbalance in the microbiome, causing skin irritation and inflammation.

Lifestyle choices and skin microbiome

Stress, lack of sleep, smoking, and a poor diet can all affect the skin microbiome. Recent studies directly connect stress, mental health, and skin conditions.
Small changes in lifestyle can lead to significant improvements and support your skin microbiota.

A holistic approach to the skin microbiome

The skin microbiota is a complex and dynamic ecosystem that constantly changes in response to its environment. This ecosystem is also affected by our overall mental and physical health, which requires a more holistic approach to understanding and nourishing the skin flora.

The gut-skin connection

The gut-skin connection is a newly recognized link between two very significant organs in the human body. The gut and skin are connected via the nervous system, hormones, and immune system, and this connection allows for communication between the two organs, impacting both physical and mental health.

The gut microbiota is home to billions of microbes, including bacteria, fungi, and viruses, and these microbes play a significant role in digestive function, metabolism, and immunity. The skin microbiome is also home to a diverse community of microbes protecting against infection and keeping the skin healthy.

Recent research has shown that the gut microbiome can influence the skin microbiome. For example, certain bacteria in the gut can produce substances that promote inflammation in the skin, leading to skin conditions like acne, eczema, and psoriasis. Therefore, maintaining a healthy gut microbiome is an important factor in keeping the skin healthy.

The gut-skin connection is a complex and newly understood link between the two vital organs. More research is needed to understand how the gut and skin interact, but it is clear that they significantly impact each other's health. Taking care of your gut health is necessary to maintain overall health and prevent chronic diseases.

The brain-skin connection

The connection between good mental health and skin is well-documented. Although the exact cause for different skin conditions is still unknown, stress is considered to be an active factor for many skin problems, from acne to psoriasis.

While the exact mechanism by which stress affects the skin is not fully understood, it is clear that the two are connected. Stress also leads to changes in hormones, inflammation, and the immune system, all of which can impact the skin's health. It can also affect the skin microbiota, leading to imbalances that can further aggravate skin conditions.

Lifestyle choices

A healthy diet greatly influences the gut microbiota, the immune system, and overall health.
Skin microbiota also requires a balanced “skin” diet that provides different bacteria with their preferable food. Here is how some nutrients affect the skin flora.


Prebiotics are different types of sugars or food that feed the skin’s good bacteria.


Probiotics are live bacteria similar to those found naturally in the gut and skin. When applied to the skin, they can help restore balance to the microbiota and reduce inflammation.


Postbiotics are fermentation byproducts produced by bacteria.

The latest research shows that skin care products with prebiotics, and postbiotics help get healthy microbes back into balance.

Regular exercise

The connection between gut microbiota and exercise has been documented in different studies, but there is less scientific evidence that directly connects activity and the skin microbiome.

An interesting study published in 2013 showed that human-to-human contact during sports results in the dispersal of microorganisms and changes in the skin microbiota.

Chronic inflammation

Chronic inflammation contributes to the exacerbation of many skin conditions, including acne, eczema, and psoriasis. The skin microbiota plays a critical role in regulating inflammation and maintaining skin health. The skin microbiota's imbalance can lead to chronic inflammation, exacerbate existing skin conditions, or even create new ones.

One key player in the relationship between chronic inflammation and the skin microbiota is a group of bacteria known as Cutibacteria acnes (C. acnes). C. acnes is a normal resident of the skin microbiome, but it can become overgrown in certain conditions. When this happens, C. acnes can produce compounds that trigger inflammation.

C. acnes is most commonly associated with acne, but it can also play a role in other chronic inflammatory skin conditions like eczema and psoriasis. Some researchers believe that C. acnes may be a common factor in all three skin conditions.

C. acnes is a normal resident of the skin and it is not related only to skin conditions. It has also been linked to preventing premature aging through UV filtering and providing other benefits to overall skin health.

There is still much to learn about the relationship between chronic inflammation and the skin microbiome, but researchers are beginning to unlock some secrets. By understanding how these two factors interact, we may be able to develop new treatments for chronic inflammatory skin conditions.

Microbiome and immune system

The skin microbiota does more than just protect the skin from harmful bacteria, it also plays a role in maintaining immunity. Studies have shown that the skin microbiota can influence the development and function of immune cells (63).

The skin flora is thought to be involved in several aspects of immunity, including regulating inflammatory responses, producing antimicrobial peptides, modulating T cell responses, and stimulating dendritic cell function.

All of these functions are involved in maintaining a healthy immune system. Disruptions to the skin microbiota can lead to immunodeficiency, which can increase susceptibility to infections and other diseases.

Signs you suffer from an imbalanced skin microbiome

Changes in the composition of the skin flora can lead to skin problems such as infections, inflammation, and allergies. Here is a list of some typical signs of an imbalanced skin microbiota.

  1. dry, dehydrated skin
  2. allergies
  3. skin infections and irritations
  4. premature aging
  5. various skin conditions like alopecia, psoriasis, acne, dermatitis, etc.
  6. breakouts

The skin microbiome and common skin conditions

Combined, skin conditions are considered the fourth leading non-fatal disability worldwide. There is a growing body of evidence linking the composition of the skin microbiota to various skin conditions. Multiple studies have shown that changes in the skin microbiome may be associated with acne, eczema (atopic dermatitis), and psoriasis.


Skin diseases can be caused by an imbalance in the skin microbiota. For example, acne is thought to be caused by a type of bacteria called Cutibacteria acnes. This bacterium is normally found on the skin, but it can overgrow and cause acne when the balance of other bacteria on the skin is disturbed.

Atopic dermatitis

Atopic dermatitis (AD) is a chronic, inflammatory skin condition that affects millions worldwide. The exact cause of AD is unknown, but it is believed to be linked to an overactive immune system and a disruption in the skin microbiota where the proportion of fungi increases to the detriment of bacteria.

There is an imbalance in the types of microbes present on the skin in people with AD. There is no cure for AD, but there are treatments that can help relieve symptoms and improve quality of life. It may also go away by identifying the root cause triggering the imbalance. Often, it is suggested to limit the number of products used in our daily life, from cosmetics to detergents... not forgetting the shampoo and conditionners. Many irritants and allergens are hidden in products, and they disturb the balance of the skin microbiota.

Seborrheic dermatitis

Seborrheic dermatitis is another widely spread skin condition that seems to be related to the skin microbiota. The exact cause of seborrheic dermatitis is unknown, but it is thought to be related to an overgrowth of a type of yeast that naturally lives on the skin. This overgrowth can be triggered by several factors, including stress, hormones, and certain medications.

While there is no cure for seborrheic dermatitis, there are treatments that can help to control the symptoms. One approach is to use medicated shampoos and creams that can help to reduce the amount of yeast on the skin and relieve itching and inflammation.

Probiotics are another treatment option for seborrheic dermatitis, and they can help restore the balance of bacteria on the skin and reduce the overgrowth of yeast.


Psoriasis is a chronic inflammatory condition of the skin that is thought to be a combination of genetic and environmental factors. It is characterized by red, scaly patches on the skin. Recent studies have shown that the gut microbiome plays a key role in psoriasis. There is evidence that certain bacteria may trigger inflammation in the gut eventually leading psoriasis, a systemic syndrome.

The skin microbiome may play a role in the development and severity of psoriasis. In particular, certain bacteria may trigger inflammation in the skin, exacerbating psoriasis. Recent studies make many connections in this direction, although more research is needed to understand the exact role of the skin microbiome in psoriasis.

Alopecia Areata

Alopecia areata is an autoimmune disease that results in hair loss. This condition's exact cause remains unknown, but it seems to be related to a person's immune system attacking their own hair follicles.

Research has shown that there may be a link between the skin microbiome and alopecia areata, as the condition has been found to be more common in people with certain types of bacteria on their skin.

Final thoughts

The skin microbiome plays an important role in skin health. A healthy balance of microbes is necessary for maintaining healthy skin. There are several ways to promote a healthy skin microbiome, including practicing general good hygiene such as enough sleep and avoiding excessive stress, avoiding over-washing, using gentle cleansers at neutral pH, encouraging an acidic microenvironment of the skin and providing pre-biotics and post-biotics to the skin microbes so they remain healthy and balanced,  as well as eating a healthy balanced diet.

The microorganisms on the skin help protect us from pathogens, provide compounds essential for human skin health, prevent premature aging, and assist in wound healing. Disruptions to the skin microbiome can lead to skin conditions such as acne, eczema, and AD.

As research into the skin microbiome continues, we will likely get a better understanding of the importance roles of these microbes for human health.

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