Evaluation of Total Eosinophil Counts, Serum Allergen-Specific IgE and Related Cytokines in Dogs with Atopic Dermatitis

Canine atopic dermatitis (AD) is a chronic allergic skin disease in which various immunological markers have been investigated. While peripheral eosinophil counts, serum allergen-specific immunoglobulin E (IgE), and cytokines have each been evaluated in allergic disorders, their simultaneous assessment in dogs with AD has rarely been reported in Korea. This study aimed to evaluate the diagnostic and clinical utility of these parameters in affected dogs. A total of 93 dogs were included between August 2019 and February 2020, comprising 65 dogs diagnosed with AD and 28 healthy controls. Clinical information, peripheral blood eosinophil counts and ratios, serum allergen-specific IgE using a multiple allergen panel (60 allergens), and cytokines related to T helper 2 (Th2) and T regulatory (Treg) cells (IL-4, IL-13, IL-31, TGF-β1) were analyzed. The mean age of AD dogs was 6.34 ± 3.99 years, with a predominance of small breeds and males. Eosinophil counts and ratios showed no significant difference between groups. In contrast, allergen-specific IgE levels were significantly elevated for several allergens, including <i>Dermatophagoides pteronyssinus</i>, <i>Acarus siro</i>, <i>Tyrophagus putrescentiae</i>, alder/birch, hazel, oak, cladosporium, and selected dietary antigens (pea, soybean, pumpkin, apple) (<i>p</i> < 0.05). Sensitization rates were also higher for <i>Acarus siro, Tyrophagus putrescentiae</i>, oak, and sheep sorrel (<i>p</i> < 0.05). Th2-related cytokines tended to increase and TGF-β1 tended to decrease in AD dogs, though without statistical significance. These findings indicate that peripheral eosinophil counts have limited diagnostic value, whereas allergen-specific IgE testing provides clinically useful information for the diagnosis and management of canine AD. Further research stratifying disease stages and assessing local tissue cytokine expression is warranted.