Exploring the Skin Microbiome

Although it may not seem like it to the human eye, there are thousands of microscopic organisms living on the surface of every person’s skin, including bacteria, viruses, mites, and fungi. The skin is not the only place in the human body where microorganisms reside. Thousands of microscopic organisms are located in the gut especially because of the ideal conditions. The skin, however, has much less suitable conditions for the growth of microorganisms. It comparatively lacks nutrients and is dry and acidic. Yet the skin still supports a wide diversity of these microorganisms. These organisms are nonpathogenic and actually help the skin. They provide an extra layer of protection against outside sources and fight against pathogens. Cutibacterium acnes, for example, creates metabolites which can break down chemicals, to drive away pathogens. The organisms also help the T-cells in the immune system recognize pathogens and fight against future pathogens. The microbiome is first developed at birth; the microorganisms expose the immune system to the nonpathogenic organisms while helping it recognize pathogenic organisms as well. The microbiome continues to grow and change until puberty, where the microbiome begins to set in stone and stay the same.  In fact, the lack of these organisms on the skin can cause issues, such as increased infections or skin disorders. The diversity of these microscopic organisms can be determined by physical characteristics of the host, the environment, the genes and lifestyle of the host, and the immune system. They are impacted by pH levels, the lay out of the skin, the moisture of the skin, and the oiliness of the skin. 

As people get older, both internal and external factors impact the functional and structural changes that happen in the skin. The microbiome is primarily impacted by the internal changes. As people get older, the microbiome grows, but not proportionally. The amount of some species of bacteria grows while the species of others diminishes. The gland that produces oil on the face gets smaller as people get older, and the amount of lipids and natural moisturizers increase. This increases the amount of some species of bacteria and decreases the amount for others. However, some of the species that decrease in aged skin produce important elements that help defend against pathogens, which then in turn increases the risk for infection. 

It’s important for skin to be hydrated to be healthy, and using skin care products can aid with this. In dry and hydrated skin there is a difference in the microscopic organisms present, but the level of hydration may not impact the amount of microorganisms. Some of the organisms most impacted by moisture and oil levels in the skin are Propionibacterium, Corynebacterium, and Staphylococcus, and only Propionibacterium is highly influenced by hydration levels. Typically, these bacteria are more impacted by the amount of oils present in the skin, but in hydrated skin more of these bacteria were present. Certain bacteria in this species can cause acne, so in more hydrated skin, acne can be more likely. Otherwise, moisture and oil levels do not have a direct impact on the number of microorganisms present and do severely impact the microbiome of the skin in any way.

Cutibacterium acnes and Staphylococcus epidermidis are two other bacteria that are commonly associated with acne. They are a necessary part of the skin microbiome but can become a problem when there is an imbalance in the microbiome. A lot of skin care products include ingredients to stunt the growth of these bacteria, but it is important that these ingredients don’t in turn reduce the diversity of the microbiome. Skin care products stop acne in a couple of ways. Firstly, by supporting nonpathogenic growth of these bacteria and secondly targeting the growth of the specific bacteria.

Using probiotics can support nonpathogenic growth of bacteria such as Staphylococcus epidermidis. Many probiotics are mainly composed of lactic acid from the bacteria genus Lactobacillus. While using skin care products can be helpful to help maintain a healthy moisture level, it is also important to consider the effects of the products on the skin microbiome. Too much moisture can cause an imbalance in the microbiome, which can lead to bacteria becoming pathogenic. It’s important to use skin care products that hydrate the skin, but then also encourage nonpathogenic growth. 










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