What’s New in Understanding the Skin Microbiome

Based on a presentation by Deirdre Hooper, MD

Watch the video of this Skincare Academy presentation featuring Dr. Hooper at https://jcad.tv/sca-deirdre-hooper-understanding-skin-microbiome/

Dr. Hooper is with Audubon Dermatology in New Orleans, Louisiana.

The microbiome is essential to skin health. We are continually discovering new species and new strains of those species. We’re continuing to understand the complex interactions between microbes and between the microbes and our bodies, and discover which of those interactions are competitive and which are synergistic. As we learn to manipulate the microbiome with prebiotics, probiotics, and postbiotics, we’re going to see advances in skin health and beauty.

The skin microbiome comprises the microorganisms that inhabit our skin, and it is essential—it interacts with our immune system to protect us against pathogens, and it produces metabolites, including vitamins, amino acids, and antioxidants, which can be beneficial to us. These organisms are abundant. There are up to one billion bacteria in every square centimeter of your skin. The number and diversity of your microbiome is determined at birth. A Cesarean section or vaginal birth affects the seeding of the microbiome. Your mother’s genetics affect your microbiome. Your sex, and as time goes by, your age affect your microbiome. This is an important point when you’re talking to patients.

Twelve to 20 percent of the microbiome can be manipulated by extrinsic factors. Environmental changes, such as moving to a new city or changing water filters, might change your microbiome. Lifestyle factors, such as your job, your hygiene level, your stress level, or your diet, all might influence your microbiome. Skin microenvironments, or biogeography, are the different areas of the skin. The microbiome varies depending on this biogeography. In moist areas of the skin, you will find bacteria that like water, such as Staphylococcus and Corynebacterium. In oily, sebaceous areas of the skin, you’ll find lipophilic bacteria, including Propionibacterium, Cutibacterium, and Corynebacterium. Drier areas of the skin have the most diverse bacteria but the lowest biomass. None of this is super surprising to us who are treating infections and rashes that commonly occur in consistent locations in the skin. 

This presentation is focused mainly on bacteria, but our skin also has a mycobiome and a virome. Similar to the microbiome, the mycobiome varies based on biogeography, with Malassezia species being the main fungal commensals. This is why we see certain rashes like tinea versicolor in certain locations. The virome is highly individualized, with many organisms of the virome being bacteriophages that infect prevalent bacteria. Research into these two areas lags behind bacterial microbiome studies because there is a lower relative abundance on the skin compared to bacteria and there are certain technical challenges associated with extraction and characterization of the mycobiome and virome. 

Microbiome changes and disease

Dysbiosis is defined as changes in the microbiome that lead to a disease state. We see this frequently in acne, atopic dermatitis, rosacea. Promoting a healthy microbiome can restore healthy skin, and we can utilize topical and oral microbiome restoring products to achieve this.

Microbiome changes and aging

Interestingly, we can determine a person’s age from their skin microbiome. As time goes by, the microbiome is influenced by extrinsic factors and changing hormones. There is a reduction in relative Cutibacterium acnes abundance, which is observed on the cheeks, forehead, and forearms with increasing age. Additionally, we can observe a decreased overall bacterial diversity with age. This decrease can reduce the benefits of these bacteria acting upon the skin and interacting with the other organisms present there. This decreased diversity can even influence the signs of aging, including pigment, wrinkles, and sun damage.

So, what can we do to address this? Creating and maintaining a healthy skin microbiome has been somewhat of a hot topic lately. The purpose of many topical and oral cosmeceuticals and nutraceuticals is to create and maintain a positive, balanced skin environment that can compete against possible pathogenic organisms for space and nutrients. The challenge here is identifying which patients would benefit from manipulation of their microbiome, and determining which products actually have a positive effect on the microbiome. 

In a review of the microbiome and skin aging, Woolery-Lloyd et al (Woolery-Lloyd H, et al. J Cosmet Dermatol. 2023) found that pre-, post-, and probiotics can increase skin hydration, decrease rhytides and pigmentation, and increase UV protection. For example, thermal spring water, which contains several prebiotics (e.g., water, carbon, nitrogen, essential elements) has been shown to yield changes in the microbiome within seven days of treatment by feeding healthy bacteria. 

Topical probiotic products allow us to establish the ideal microbiome by placing the desired living bacteria on the skin. This leads to the production of postbiotics as the bacteria create metabolites; these metabolites include anti-inflammatory substances, fatty acids that modulate skin pH, and antioxidants that fight free radicals. Additionally, oral probiotics can influence the skin microbiome, leading to increased hydration, fewer wrinkles, and greater UV resistance. However, despite observing these benefits,, more research is needed on which of these products and supplements are the most effective. 

Challenges in evaluating the microbiome

Collecting and extracting microbes from the skin is a practice that remains to be refined; some microbes are not recoverable using current methods based on location or biology. Are we getting the bacteria located deep down in the hair follicles? Are we capturing every single type of bacteria? 

What’s the difference between pre-, pro, and postbiotics?

It’s important to understand the difference between pre-, pro-, and postbiotics when speaking to your patients. Mixing any one of these into a topical or oral product can influence the microbiome. 

  • Prebiotics: Something that selectively stimulates growth and/or activity of bacteria. Thermal spring water and oat extract are commonly used prebiotic agents. 
  • Probiotics: Living and viable microorganisms that alter the microflora of the host. If the bacteria aren’t living and viable, they do not qualify as a probiotic. 
  • Postbiotics: Nonviable bacterial products or byproducts from probiotic microorganisms, such as enzymes, antioxidants, and peptides, that have biologic activity in the host. 

Without a complete extraction of the microbes on our skin, we have yet to examine the full picture when it comes to the skin microbiome. An additional limitation of microbiome research is that it’s difficult to control. When you’re reading these studies, it’s important to realize that everyone has their own individualized microbiome that is influenced by their individual intrinsic and extrinsic factors. 

Another challenge we face is the lack of regulation of probiotic supplements. FDA-regulated dietary supplements containing probiotics cannot lawfully be marketed to cure, mitigate, or prevent any diseases. The FDA is considering ways to provide additional clarity on the supplement facts label for declaring colony forming units of probiotics and weight. 

In summary

A diverse microbiome is essential. Manipulating the microbiome can lead to improvements in skin aging and overall skin health. Current topical and oral therapies that show promise and will only improve with further research. Be on the lookout for continuing research so that you can be better educated and integrate these lessons into your practice.