Dermatology health and the microbiome: How they interact for healthy skin from within

Dermatological conditions are among some of the most common cases in practice. While dermatologic conditions are often caused by food and environmental reactions, the underlying drivers can be more complex than they appear on the surface. Emerging research shows an interconnected relationship between the gut microbiome and skin health. As the science continues to evolve, so does the case for integrating targeted nutrition as a core component of multimodal dermatologic therapy.

Q: What is “the gut-skin axis,” and why should it matter to veterinarians?

Chelsie Estey, MSc, DVM, DACVIM (Neurology): The gut-skin axis is a pathway through which the gastrointestinal (GI) microbiome can influence immune regulation, systemic inflammation and skin barrier function. Through research, we know a large portion of a pet’s immune system resides in the GI tract, which means microbial imbalances in the gut can trigger inflammation which may manifest cutaneously. This matters because it means the status quo is changing. As an industry, we can look deeper for answers to our most complex cases and explore different pathways for treatment. This starts with moving past simply asking, “What’s wrong with the skin?”, and diving deeper into how the skin and gut microbiome could be negatively influencing immune function.

Alyssa Toillion, BS, MPH, PhD: A healthy, well-balanced gut microbiome plays a pivotal role in generating key metabolites that extend benefits far beyond the intestine, reaching organs such as the kidneys, brain, heart and skin. In this way, it significantly influences a pet’s overall health. The metabolites produced by the gut microbiome can help support skin barrier function, and it is this relationship between the gut microbiome and the skin barrier that defines the gut-skin axis. For veterinarians, this matters because it means the gut microbiome can be a primary therapeutic target in dermatological cases. At Hill’s, our research into the relationship between the skin and the gut microbiome has shaped how we design and formulate our dermatological nutrition.

Q: How does an imbalanced gut microbiome contribute to skin disease in dogs and cats?

Estey: Maintaining a balanced microbiome is pivotal to the development and function of a pet’s immune system. Microbial populations are not static and can be influenced by a range of factors. When that balance is disrupted, there can be an increased risk of systemic inflammation impacting the skin barrier, while making it more permeable to environmental triggers as well. In practice, a patient presenting with signs of atopic dermatitis may in part have a gut microbiome imbalance that is actively amplifying their inflammatory state. Treating the skin without addressing the gut may be leaving a significant driver of the disease unmanaged.

Toillion: In a state of dysbiosis, the diversity and abundance of beneficial bacterial populations decline, reducing the production of protective metabolites. Simultaneously, populations of pathogenic or pro-inflammatory bacteria can increase. When this occurs, the intestinal barrier itself can become compromised, allowing harmful bacterial products to circulate and drive widespread inflammation. This can manifest in the skin as impaired barrier function, heightened immune reactivity and increased susceptibility to secondary infection. From a nutritional science perspective, we’ve seen that incorporating a diet designed to support a healthy microbiota can be an effective tool in managing this inflammatory cascade.

Q: How does a deeper understanding of the gut-skin axis change or enhance how vets should approach diagnosis and treatment?

Estey: On the diagnostic side, the interconnectedness of the gut microbiome and dermatologic health reinforces the value of a thorough patient history. Largely, the diagnostic pathway itself should not change, but understanding what is happening to the skin in addition to the gut gives us a richer picture of what we are actually evaluating. On the treatment side, the shift is more significant. It changes how we have client conversations, providing a sound rationale for positioning therapeutic nutrition as a first-line intervention, as well as an essential element of a multimodal treatment plan. Rather than presenting a therapeutic nutrition as simply "avoiding allergens," we can now explain that the nutrition is working at the microbial level to help regulate the immune response that is driving the pet's skin disease. This tends to be a more accurate and motivating rationale for compliance.

Toillion: From a scientific perspective, the gut-skin axis allows us to view the elimination diet trial not only as a diagnostic tool, but also as a concurrent therapeutic intervention for the gut. When a patient transitions to a well-formulated therapeutic food, one that includes targeted prebiotic fibers to promote beneficial bacterial populations, the nutrition helps to restore the microbial environment while minimizing exposure to potential food antigens. In dermatologic cases, veterinarians commonly apply an evidence-based diagnostic approach with nutrition integrated as a core element of multimodal therapy. By incorporating the gut as a part of this treatment strategy, clinicians can open an additional pathway to improved patient outcomes.

Q: What specific nutritional ingredients should veterinarians be looking for when selecting a therapeutic diet for a patient with a dermatological condition, and how do they work?

Estey: When thinking about dermatologic nutritional recommendations for a patient, try to look for ingredients that address the condition from multiple angles simultaneously. For patients with a suspected adverse food reaction, a hydrolyzed animal protein or a single novel animal protein formula is likely the best option, as they can reduce food-mediated immune responses. For an atopic or chronic inflammation patient, ingredients such as vitamin E, omega-3 fatty acids and antioxidants all play different but important roles in supporting dermatological conditions in cats and dogs. Increasingly, I encourage practitioners to look for foods that incorporate targeted prebiotic fibers, which can selectively promote the activity of beneficial bacterial populations, because we know from the science that microbiome support is a meaningful part of managing these cases long-term.

Toillion: When environmental triggers and food sensitivities are left untreated, the resulting histamine and cytokine release creates a cycle of skin irritation that can be hard to break. Therapeutic nutrition works to interrupt that cycle at multiple levels, particularly formulas with targeted prebiotic fibers that selectively enrich beneficial gut bacteria. As these bacteria ferment prebiotic fibers, single novel animal proteins and hydrolyzed proteins each contribute in different ways to avoiding immune reactivity to food antigens. Omega-3 and omega-6 fatty acids help modulate inflammation while reinforcing the skin's barrier, and bioactives and phytonutrients help normalize the immune response to environmental triggers. The inflammation is further mitigated by antioxidants, including vitamin E, which protect cells from oxidative damage. Together, these nutrients are most effective when integrated together into a cohesive nutritional approach grounded in microbiome science.

Q: What should veterinary teams know about therapeutic nutrition, and how can it be practically integrated into dermatological treatment plans?

Estey: Nutrition should be incorporated as a first-line intervention, as well as an element within a multi-modal treatment plan. Nutrition is constantly working to support the gut environment that supports immune regulation and skin barrier function. When a patient presents with dermatological signs, initiating therapeutic nutrition at the first visit puts the gut-skin axis to work from day one. Hill’s Prescription Diet has several options designed specifically for that entry point. Prescription Diet Derm Complete and z/d are designed specifically for these cases. When making the recommendation, it may also be worth reframing therapeutic nutrition in client communication. Center conversations on what the food is doing biologically, and how it works. For veterinary health care teams who want to dive deeper into the clinical science behind this nutrition, I would strongly encourage registering for Hill’s Global Symposium this June. The program is free and dedicated entirely to the gut-skin axis.

Toillion: Just as individual nutrients work synergistically to support specific conditions, I’d encourage veterinary healthcare teams to seek therapeutic diets that go beyond simply limiting allergen exposure or managing food sensitivities. Products that actively support the gut microbiome through targeted nutrients like prebiotic fiber blends while also helping to address systemic inflammation are ideal. In other words, the most effective nutritional strategies are formulated with the microbiome as a core design principle, not an afterthought. This microbiome-centered approach is exactly what I’m proud to investigate in my work at Hill’s. At Hill’s Global Symposium, I will be sharing insights on the positive dermatologic impacts of a hydrolyzed protein food with a specialized prebiotic fiber blend in adult dogs. I invite all practitioners and researchers interested in the gut-skin axis to join us, as we deepen our understanding of overall pet health and the far-reaching systemic influence of the microbiome.