Gut-Skin Connection: How Your Microbiome Impacts Autoimmune Skin Diseases
The gut and the skin are the two biggest surfaces of the human body. Each of them measures about 25-30 square meters and is home to billions of microbes, known as the microbiome. They’re both places that shield us from the external environment. Because of their roles in immunity, they’re also sites where autoimmunity tends to occur (1). While seemingly separate entities, the gut and the skin influence each other in many ways.
The Gut-Skin Axis, Explained
The communication between the gut microbiome and the skin is known as the gut-skin axis. “It’s an emerging field, but we know that the microbes in our gut can influence immune function in the skin, as well as other cell types,” says Martin Kriegel, Chair of Rheumatology and Clinical Immunology at the University of Münster.
This relationship between gut microbes and the skin is a bi-directional relationship. For example, people with inflammatory bowel disease may also have inflammatory skin disease (2). Other studies have found that skin damage leads to changes in the gut microbiome (3). “Stress from the outside leads to stress on the inside. Stress from the inside leads to stress from the outside,” notes Chris Callewaert, a microbiologist and bioengineer at Ghent University, as he describes the gut-skin axis.
How can the Gut Microbiome affect Skin Health?
Kriegel notes that one way that gut microbes impact the skin is through the metabolites they produce. When secreted into the bloodstream, these metabolites can have far reaching effects (4). “Many organs outside of the gut can be influenced by gut microbes via metabolites,” says Kriegel.
Aside from the impacts of metabolites they secrete, could microbes from the gut actually travel to the skin? “Whether microbes from the gut can reach the skin is controversial and unknown, but one potential mechanism which we’ve been working on is bacteria leaving the gut, and reaching lymph nodes, liver, and spleen,” says Kriegel, who has found evidence of this movement in animal models (5) and is studying the effects of gut microbe translocation on the immune response (6).
Gut and skin microbiomes are altered in many skin autoimmune diseases. However, it’s difficult to know whether microbial changes are the cause of a skin disease or a consequence of the disease.
- Alopecia: Research finds that changes in the scalp, hair follicle, and gut microbiomes are associated with alopecia (7).
- Atopic dermatitis: People with atopic dermatitis are more likely to be colonized by bacterium Staphylococcus aureus than those without atopic dermatitis (8). People with atopic dermatitis also have decreased microbial diversity on the skin, which can allow S. aureus to grow (9). Atopic dermatitis flares have also been associated with reduced Streptococcus, Corynebacterium, and Propionibacterium bacteria, likely due to antibacterial compounds produced by S. aureus (10).
- Psoriasis: People with psoriasis have changes in their gut and skin microbiomes. There’s evidence that Propionibacterium, Staphylococcus, Corynebacterium, and Streptococcus are the main bacteria involved in psoriasis (11). People with psoriasis are more likely to develop intestinal immune diseases (4).
- Systemic Lupus Erythematosus: A study that compared the gut microbiome in people with SLE found that Bacteroides thetaiotaomicron was more abundant in those with SLE (12). The balance of bacteria that have roles in intestinal homeostasis is also altered in SLE (13).
- Vitiligo: A study that compared sites affected by vitiligo versus unaffected skin found that the microbial diversity was reduced in sites affected by vitiligo. Different types of bacteria also dominated in sites affected by vitiligo (14).
Support a Healthy Gut Microbiome through Diet and Probiotics
One of the primary ways to support a healthy gut microbiome is to focus on diet. “You are what you eat,” says Callewaert. “Our gut microbiome is shaped by what we eat for the large part. We need a lot of fiber.” He notes that the standard Western diet, which contains high levels of sugar and fats, is not ideal for our gut microbiome. Research shows that a high-fat diet increased skin inflammation in psoriasis mouse models (15). Another study found that the high-fiber Mediterranean diet correlated with lower psoriasis severity (16). Other sources recommend fermented foods to decrease inflammation and improve microbial diversity in the gut (17).
Probiotics are another popular way to promote a healthy gut microbiome, but it is hard to know whether probiotic bacteria actually make it into the intestines in high enough doses. “For some people, probiotics help, and for other people, it doesn’t help,” says Callewaert.
Can Healing the Gut Microbiome Reduce Autoimmune Skin Disease Flares?
While it’s possible that taking measures to heal the gut microbiome can help manage autoimmune skin diseases, it’s complicated. “There’s a strong link between diet, gut microbiome and autoinflammatory diseases,” says Callewaert. “But there are so many factors, like lifestyle and stress, that play a role in the gut. It’s difficult to control them all.“
“I strongly believe that by managing your gut, you can also manage autoinflammatory disease or reduce it for large parts,” says Callewaert.
Potential Future Microbiome-based Treatments for Autoimmune Skin Diseases
Many biotech companies are beginning to work on topical probiotics that can be applied directly to the skin. “It’s less studied compared to oral probiotics. But it definitely has a future,” says Kriegel. “We need to better figure out how probiotics stick to the skin and remain there.”
“It’s still the early days. Hopefully some new preventative measures and therapies will come out in the coming years that aren’t just medication to suppress the immune system,” says Callewaert.
About the Author
A microbiologist turned freelance science writer who works with life science companies, nonprofits, and academic institutions on anything from news stories, explainer articles, and content marketing. She shares the wonderful world of microbes on her blog The Microbial Menagerie.
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