Effects of underlying conditions on skin hydration and sebaceous gland activity in dogs with otitis externa

Otitis externa is a common inflammatory condition of the canine ear canal, often associated with underlying dermatological and endocrine disorders. This study aimed to investigate the effects of these conditions on skin hydration and sebaceous gland activity in dogs diagnosed with otitis externa. A total of 220 dogs, including 200 with otitis externa and 20 healthy controls, were examined. Dogs were categorized based on underlying conditions, including atopic dermatitis, hypothyroidism, Cushing’s disease, parasitic infestations, allergies, and a heterogeneous "other" group. Skin hydration and sebum levels were measured using non-invasive tools, and microbial cultures were analyzed from ear canal samples. Results revealed significantly higher hydration and sebaceous activity in dogs with Cushing’s disease and atopy, while hypothyroid dogs exhibited lower sebaceous output. A strong positive correlation (r = 0.787, p< 0.001) was observed between hydration and sebum levels, which were also associated with increased microbial colonization, particularly by Malassezia pachydermatis and Pseudomonas aeruginosa . These findings emphasize the importance of identifying patterns in skin physiology among predisposing conditions to improve prevention and targeted treatment of otitis externa. This study highlights the role of dermatological homeostasis in the pathogenesis of otitis externa and supports integrating skin hydration and lipid assessments into routine diagnostic and therapeutic protocols.