The skin microbiome is the bacterial environment of our skin. Similar to the gut microbiota, it is an essential part of the organs immune function and appears to be contribute to it’s ability to maintain stability.
Some important roles that the skin microbiome appears to play, include:
- Modulate the skin’s immune response
- Assists in the production of antimicrobial compounds
- Directly protects against competing micro-organisms
Accordingly, issues in the skin microbiome may make a significant contribution to various skin disease and their progression. And though the skin microbiome was discussed in significant detail earlier in this book (in the Skin Chapter), this section simply summarizes and reviews some key points.
The microbiome or the microbiota
Medical professionals commonly use the words microbiota and microbiome interchangeably. To keep things simple, this book uses the word microbiome when referring to the skin bacteria and microbiota when discussing the gut.
A Healthy Skin Microbiome
Researchers have made tremendous efforts into finding patterns in skin microbiome which may be representative of stability and healthy function. However, to-date there has been very little agreement on what a healthy skin microbiome is supposed to look like.
Instead of finding distinct patterns, the majority of research actually revealed two district trends instead. More specifically, it began to become apparent that two of the key characteristics of a healthy microbiome are high diversity and high interpersonal variation . Basically meaning that both a large variation of microorganisms are present and the composition is fairly unique to that specific individual. No wonder that finding distinct patterns had proven difficult.
The Microbiome in Skin Disease
Finding patterns in skin microbiome proved much more rewarding in the case of skin disease. Here, specific micro-organisms were more easily identified as playing a role in specific skin disease and their relationship to disease progression was usually quite apparent.
One such example, is in the case of atopic dermatitis. In this condition, flares were seen to correlate with colonization and infection by Staphylococcus aureus and a reduction in overall diversity . But in the end, the large amount of other factors involved (diminished antimicrobial peptides, immune mutations, and defects in barrier function) left research unable to draw any specific conclusions [3, 4, 5].
And this seems to be the case in the majority of other skin conditions as well. While specific changes in the microbiome can be seen, it can be extremely difficult to determine weather this causes the skin disease or is simply the result of other defects in the skin. In general though, a reduction in the diversity of the skin microbiome does seem to be a common trait of skin disease  .
Skin Microbiome Alterations Seen in Seborrheic Dermatitis
Now if we focus our attention on the skin microbiome in seborrheic dermatitis, the malassezia fungus gets the most attention. In fact, most current treatments directly aim at controlling/reducing the malassezia population of the skin. However, some more recent research on this area has revealed some interesting data:
- No difference was seen in the abundance of malassezia species between healthy individuals and those affected by seborrheic dermatitis 
- The amount of malassezia restricta and staphylococcus epidermidis present was only slightly increased, while propionibacterium acnes was significantly decrease 
- The relationship between changes in skin’s bacterial population was more apparent then that changes in the fungi (malassezia) population 
As a result, it is possible that malassezia may only have a supplementary role in seborrheic dermatitis. And perhaps the overall microbiome composition should be given much more attention in the future.
The overall effect of antifungals is not always considered
The most common treatments for seborrheic dermatitis are antifungal agents. While they may temporarily inhibit malassezia activity, their effect on the skin microbiome as a whole is usually not considered.
In any case, it does seem that improving and stabilizing the skin microbiome may prove beneficial. And perhaps finding ways to keep the beneficial microbes happy may prove more useful in the long term then simply trying to wipe out the less favorable ones.
This section examined the intricate role the skin’s environment (the microbiome) plays in skin health and disease.. Key points include:
- The skin microbiome is an essential component of the skins immune function and has a direct impact on its stability
- Issues in the microbiome have been linked to various skin issues and the state of their progression
- High microbiome diversity and high interpersonal variation (uniqueness to individual) are the main two features of a healthy microbiome
- Domination of the microbiome by a single family of microbes, fungi or viruses is one of the clearest indicators of skin disease
- In seborrheic dermatitis, the malassezia fungi get the most attention and the majority of research blames them for disease progression
- More recent research suggests the role of malassezia may actually be secondary and a shift in the overall bacterial population could be at the main issue