Association Between Serum Vitamin D, Inflammatory Biomarkers, and Clinical Severity in Dogs with Chronic Dermatological Diseases

Abstract

Introduction: Chronic dermatological diseases are common in dogs and are often linked to persistent inflammation, immune dysregulation, and reduced quality of life. Vitamin D has important immunomodulatory and anti-inflammatory properties. This study aimed to investigate the association between serum vitamin D levels, inflammatory biomarkers, and clinical severity in dogs with chronic dermatological diseases.
Materials and methods: This case-control study included 30 dogs with chronic dermatological diseases and 30 clinically healthy dogs as controls, conducted between March 2025 and May 2026. The mean age of dogs was 4 years (1.8-7.5 years), and the mean body weight was 19.1 kg (8.5-30.5 kg). Of the 15 male dogs, 10 were neutered, and of the 15 female dogs, 12 were spayed. The clinical severity of dermatological diseases was assessed by the Canine atopic dermatitis extent and severity index, 4th iteration, and the Pruritus visual analog scale. Blood samples were collected on day 1 from all dogs for serum Vitamin D, C-reactive protein (CRP), and interleukin-6 (IL-6) measurements. Complete blood counts were obtained, and the neutrophil-to-lymphocyte ratio (NLR) was calculated on day 1. At the end of the study period, dogs affected by dermatological diseases and healthy dogs were compared for serum vitamin D levels and inflammatory biomarkers.
Results: Dogs with chronic dermatological diseases had significantly lower serum vitamin D levels and higher CRP (12.4 mg/L), IL-6 (42.6 pg/mL), and NLR (4.8) than controls. Lower vitamin D status in dogs with chronic dermatological diseases correlated with higher clinical disease severity and higher pruritus scores. Vitamin D concentrations negatively correlated with CRP, IL-6, and NLR, whereas CRP and IL-6 positively correlated with clinical severity in dogs with chronic dermatological diseases. The current results indicated that lower serum vitamin D levels were significantly associated with more severe dermatological manifestations after adjusting for age, body weight, sex, and neuter status.
Conclusion: The current results demonstrated that decreased serum vitamin D levels were associated with increased systemic inflammation and increased clinical severity in dogs with chronic dermatologic diseases. Thus, serum vitamin D levels and inflammatory biomarkers can serve as an adjunctive indicator of disease severity in dogs.