Update on the role of genetic factors, environmental factors and allergens in canine atopic dermatitis.

Background: Canine atopic dermatitis (cAD) is a common, complex and multifactorial disease involving, among others, genetic predisposition, environmental factors and allergic sensitisation.

Objective: This review summarises the current evidence on the role of genetic and environmental factors and allergic sensitisation in the pathogenesis of cAD since the last review by ICADA in 2015.

Materials and methods: Online citation databases and proceedings from international meetings on genetic factors, environmental factors and allergens relevant to cAD that had been published between 2015 and 2022 were reviewed.

Results: Despite intensive research efforts, the detailed genetic background predisposing to cAD and the effect of a wide range of environmental factors still need more clarification. Genome-wide association studies and investigations on genetic biomarkers, such as microRNAs, have provided some new information. Environmental factors appear to play a major role. Lifestyle, especially during puppyhood, appears to have an important impact on the developing immune system. Factors such as growing up in a rural environment, large size of family, contact with other animals, and a nonprocessed meat-based diet may reduce the risk for subsequent development of cAD. It appears that Toxocara canis infection may have a protective effect against Dermatophagoides farinae-induced cAD. House dust mites (D. farinae and D. pteronyssinus) remain the most common allergen group to which atopic dogs react. Currently, the major allergens related to D. farinae in dogs include Der f 2, Der f 15, Der f 18 and Zen 1.

Conclusions and clinical relevance: Canine atopic dermatitis remains a complex, genetically heterogeneous disease that is influenced by multiple environmental factors. Further, well-designed studies are necessary to shed more light on the role of genetics, environmental factors and major allergens in the pathogenesis of cAD.