Canine Dermatology Update: What We Know About the Microbiome and Skin by Lisa Coder, MS, DVM 

Canine dermatology is a complicated and often frustrating subject. Dermatitis is a general term that indicates an inflammation of the skin; the reasons for the inflammation can be varied and multifaceted. Signs may include pruritus, scaling, alopecia, abnormal odor, oiliness, and changes in skin thickness or color. Diagnostic testing may be challenging, and a diagnosis may take longer than many other diseases or conditions. The latest research suggests the microbiome is more complicated than previously thought, and having a greater understanding of the interactions between the skin, the commensal organisms that inhabit it, and its response to changes can help us better treat our veterinary dermatology patients. 

The Dog’s Microbiome Makeup 

A dog’s skin is a multifunction organ that acts as a barrier against dehydration, infection, and trauma to internal organs. With an active microbiome that includes over 2,000 different microorganisms4, it is a complex environment which influences immunity, the function of the skin itself, and the overall health of the dog. The exact microbial community is affected by many factors, including genetics, diet, hygiene, and general living conditions. Changes in a healthy microbiome are associated with pathologic skin conditions often seen in veterinary dermatology, such as dermatitis, mast cell disease, or infection, although it is still unclear if these changes are a cause or effect for the observed skin disease.  

In both dogs and people, the microbiome on the skin is influenced strongly by cohabitation. Living with another animal generally leads to an increased diversity of microorganisms, although the individual populations between dogs are more similar in dogs that live together as opposed to dogs who live in another location. Dogs of the same breed are also more similar to each other when compared to phenotypically different animals4. 

Hygiene plays a large role as well, as the amount of stressors presented to the microbiome can affect the types of microorganisms present, as well as inhibit their ability to flourish. If the microbes on the skin have to expend energy to simply survive, it will decrease their effectiveness in preventing colonization of pathogenic organisms and will greatly influence the overall health of the dog. Overcleaning, such as bathing too frequently, can also negatively affect the skin microbiome and cause many similar problems. 

The Protective Role of the Microbiome in Canine Skin Disease 

The types of microbes found most commonly on canine skin often express genes that are vital for providing protection to the dog. These include bacterial genes that code for resistance to colonization of pathogenic bacteria, such as production of antimicrobial peptides, other proteins that aid in protection from oxidative stress, and substances that inhibit the formation of biofilms2,4. These commensal microorganisms provide an important barrier to colonization of disease-causing microbes and provide resistance to infection, maintain the ability of the skin to protect the tissues and organs internal to it, and help dogs produce a healthy hair coat.  

Allergic Dermatitis and the Changes in Microbiome 

Atopic dermatitis is one of the most common challenges in canine dermatology, affecting approximately 10% of dogs1,3. These dogs suffer chronic bouts of intense pruritus, alopecia, scaling, and erythema. Sensitization and reaction to environmental allergens is the driving factory behind atopy and is often genetically predisposed. Atopic dermatitis is mediated by Immunoglobulin-E (IgE) and is usually first observed between 6 months and three years of age in dogs, although can appear at any age.  It is difficult or nearly impossible to diagnose allergies, but instead testing focuses on identifying specific allergens which cause adverse clinical signs. Signs often begin as a seasonal issue, but can expand and eventually manifest during the entire year.  

Food allergies are far less common in canine dermatology patients, but can be similar in presentation to atopic dermatitis. However, there is no seasonality, and elimination of the offending ingredient will eventually lead to resolution of clinical signs within 3-4 months. Elimination diets should not include any ingredients the dog has previously been ingesting, and even treats need to be closely monitored. Evidence for microbiome changes in dogs with food sensitivities has not been well studied. Indeed, a true IgE allergy to food products has not been definitively proven1.  

All of these conditions can lead to opportunistic infection with colonizing bacteria such as Staphylococcus pseudintermedius, which is present in higher numbers in dogs with atopy2. Dogs with atopic dermatitis have distinctly less biodiversity in their skin microbiome than dogs without chronic skin disease, even when the atopic dog was not experiencing an active allergic episode,2,3,4. 

Topical treatment with a commercially available chlorhexidine and miconazole shampoo resulted in a mildly increased diversity in microorganism population, but showed no difference between atopic and clinically normal dogs3. Often in veterinary dermatology, dogs with atopic dermatitis show improvement with similar medicated shampoos. This may be due to other soothing ingredients as well as reducing the prevalence of secondary infections which can drastically worsen clinical signs.  

Online Veterinary Dermatology Certificates: The Way to Better Canine Dermatology 

Understanding the microbiome only takes a veterinarian so far – canine dermatology is a complex and intricate field of study. Free online veterinary CE can provide what appears to be some simple ideas to manage the allergic dog, but a simple solution to a problem so complex rarely works. A comprehensive education in veterinary dermatology, such as a certificate program, offers an in-depth exploration of the many components that affect a dog’s skin and gives you the skills and confidence you need to treat these patients.  

Improve Veterinary Education provides an excellent certificate course to explore the intricacies of veterinary dermatology, and a greater understanding of how the environment, the microbiome, and the skin of the dog interact to produce the diseases often encountered in canine dermatology. This online veterinary certificate program leads to an internationally recognized qualification, which can help a veterinarian distinguish themselves in the complicated field of veterinary dermatology.  

Find out more about the online veterinary dermatology certificate to gain confidence and springboard your career in canine dermatology today!  

Works Cited

Bourguignon, Elisa & Matos, Luciana & Ferreira, Tássia & Favarato, Evandro. (2012). Dermatology in Dogs and Cats. 10.5772/53660. 

Rodrigues Hoffmann A, Patterson AP, Diesel A, Lawhon SD, Ly HJ, Elkins Stephenson C, Mansell J, Steiner JM, Dowd SE, Olivry T, Suchodolski JS. The skin microbiome in healthy and allergic dogs. PLoS One. 2014 Jan 8;9(1):e83197. doi: 10.1371/journal.pone.0083197. PMID: 24421875; PMCID: PMC3885435. 

 Suttiwee Chermprapai, Thomas H.A. Ederveen, Femke Broere, Els M. Broens, Yvette M. Schlotter, Saskia van Schalkwijk, Jos Boekhorst, Sacha A.F.T. van Hijum, Victor P.M.G. Rutten. The bacterial and fungal microbiome of the skin of healthy dogs and dogs with atopic dermatitis and the impact of topical antimicrobial therapy, an exploratory study. Veterinary Microbiology 229. 2019. https://doi.org/10.1016/j.vetmic.2018.12.022 

Whittle, M.J., Castillo-Fernandez, J., Amos, G.C.A. et al. Metagenomic characterisation of canine skin reveals a core healthy skin microbiome. Sci Rep 14, 20104 (2024). https://doi.org/10.1038/s41598-024-63999-5 

Author: Lisa Coder, MS, DVM