Trillions of bacteria normally live within and on our bodies. Their byproduct is known as the microbiome. Normally, these bacteria live in harmony as a community. There are many different types of microbiome communities in the body, ranging from the gut microbiome to the mouth microbiome to the skin microbiome. In eczema, medical researchers have looked closely at the skin microbiome and compared how it changes in the presence of eczema.
The Skin Microbiome Shifts in Eczema
The microbiome make-up and diversity appears to shift in those with eczema, especially when their eczema becomes inflamed and flares. Medical researchers have looked at this closely by following people with eczema before, during, and after a flare of their eczema. They found that when eczema was well controlled, the skin microbiome was more diverse, and the microbiome diversity decreased during a flare. In other words, there was a greater number of different bacteria on the skin before an eczema flare and the number of different bacteria decreased during a flare. The researchers went one step further to identify Staphylococcus aureus as the bacteria that became dominant during an eczema flare. The shift in the microbiome toward Staphylococcus aureus occurred even before the eczema flared, raising the possibility that subtle shifts in the microbiome might predict an eczema flare. Once the eczema was brought under control with treatment, the skin microbiome returned to a state where balance and diversity of the bacteria were restored.
The researchers conducted a second study where they looked at how bacterial communities were different between children with more severe eczema compared to those with less severe eczema. Children with more severe eczema tended to have an overgrowth of the Staphylococcus aureus strain while those with less severe eczema had an abundance of Staphylococcus epidermidis, which is often a part of the normal skin bacteria. In this study, the researchers then took the same Staphylococcus aureus bacteria and applied it to the skin on the back of mice, and this triggered a response in the mouse’s skin to react with inflammation similar to what is seen in eczema. This study shows that the Staphylococcus aureus bacteria may partially drive the inflammation that is seen with severe eczema outbreaks.
An Increased Microbiome Diversity May Be Healthier
Diverse microbiome communities are rich in many different types of bacteria and have been associated with healthier skin in eczema. In the case of eczema, there appears to be a predominance of the Staphylococcus aureus when there is a flare. However, when the microbiome remains diverse, it appears that Staphylococcus aureus is not able to overgrow. The reasons for this remain unclear but may be because other species of bacteria compete with Staphylococcus aureus for resources and keep each other from overgrowing.
Strategies to Keep the Microbiome Diversified
Researchers are looking for ways to restore a healthier microbiome in people with eczema. Two approaches are either to prevent the microbiome from shifting to an unhealthy state or to restore a healthy microbiome quickly as soon as there is an eczema flare.
- Bleach baths: Dilute bleach baths are similar to a swimming pool. The dilute bleach is not irritating to the skin but can help improve eczema.
- Antibiotic ointment in the nose: It turns out that the nose is a rich source of bacteria for the rest of the body. Researchers have shown that eczema could be improved by using bleach baths along with treatment of the nose with mupirocin (an antibiotic) to reduce Staphylococcus aureus. 
- Regular moisturizer use: Moisturizers help keep the skin hydrated. This helps to prevent bacteria living on the skin surface from entering the skin to cause infection and allergy. Regular moisturizer use helps to keep the microbiome diversified.
- Antibiotics: Antibiotics can help restore balance to the skin’s bacterial community when there is an overgrowth of one bacterium, such as Staphylococcus bacterium. If there is fever, yellow-crust, or pus draining from the skin, a physician needs to immediately evaluate the skin. Although antibiotics will kill off both good and bad bacteria, it allows for the skin to have a restoration of balance.
- Steroids: Topical steroids are effective in reducing inflammation and in treating eczema flares. The use of steroids to reduce inflammation is associated with reducing the dominance of aureus.[2,7] The goal with steroids is to use them for a short time to reduce flares and then transition to non-steroid based therapies for maintenance.
While proactive approaches may not be able to totally eliminate eczema flares, they may decrease the frequency and severity of eczema flares, thereby decreasing the need for reactive approaches.
Microbiome research is an exciting and growing area of research. Changes in the skin microbiome are closely associated with eczema, but we still do not fully understand how the different bacteria are interacting with each other and our immune system.