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

## TL;DR

This study evaluates blood markers in dogs with allergic skin disease, finding that allergen-specific IgE testing is more useful than eosinophil counts for diagnosis.

## Contribution

The study is one of the first in Korea to simultaneously assess eosinophils, IgE, and cytokines in canine atopic dermatitis.

## Key findings

- Eosinophil counts showed no significant difference between dogs with atopic dermatitis and healthy controls.
- Allergen-specific IgE levels were significantly elevated for several allergens, including house dust mites and certain pollens and dietary ingredients.
- Th2-related cytokines showed trends but lacked statistical significance in dogs with atopic dermatitis.

## Abstract

Canine atopic dermatitis (AD) is a common allergic skin disease that often causes itching and discomfort in dogs, leading to reduced quality of life. To better understand the usefulness of blood-based tests in dogs with AD, we examined eosinophil counts, serum allergen-specific immunoglobulin E (IgE), and several cytokines related to allergy and immune regulation. Ninety-three dogs were enrolled, including 65 diagnosed with AD and 28 healthy controls. We found that eosinophil counts were not significantly different between affected and healthy dogs, suggesting limited diagnostic value. However, allergen-specific IgE testing showed higher levels and sensitization rates to several common environmental and food allergens, particularly house dust and storage mites, pollens, and certain dietary ingredients. Cytokine levels showed some trends but were not significantly different. Our results indicate that allergen-specific IgE testing can provide meaningful information for diagnosis and management of AD in dogs.

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 Dermatophagoides pteronyssinus, Acarus siro, Tyrophagus putrescentiae, alder/birch, hazel, oak, cladosporium, and selected dietary antigens (pea, soybean, pumpkin, apple) (p < 0.05). Sensitization rates were also higher for Acarus siro, Tyrophagus putrescentiae, oak, and sheep sorrel (p < 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.