Definition and etiology of canine Atopic Dermatitis

What is the pathogenesis of canine Atopic Dermatitis?

cAD was first defined as a clinical dermatitis hypersensitivity linked to an inherited tendency to produce immunoglobulin E in response to environmental allergens. Currently, it's considered to be more like a T-cell mediated hypersensitivity, characterized by a complex inflammatory process sometimes associated with IgE. So it's now considered to be more of a complex clinical syndrome than a clinical disease, where the skin serves as the primary entry point for allergens.

How often is cAD diagnosed compared to Adverse Food Reactions (AFR)?

cAD is one of the most common inflammatory skin diseases in dogs, with a prevalence of up to 20% of pruritic skin diseases. Cutaneous AFR represents 1 to 2% of skin diseases and is present in 9 to 15% of dogs with cAD.

In your experience, which dogs are more prone to developing this problem?

Several breeds appear to be predisposed to cAD, with variations in lesion locations among these breeds. Lifestyle is also a factor, as dogs living in apartments seem to be more prone to this disease due to reactions to house dust mites. The mean age for the onset of cAD is about 2 years, but there appears to be a correlation between age and breed, with French Bulldogs and Shar-Peis being affected earlier, for instance.

What clinical signs do we see in dogs with cAD?

cAD is a clinical syndrome characterized by pruritus and erythema, most frequently located on the face, paws, ventral abdomen, inguinal region, axillae, tarsus, carpus, and external ear canal. When pruritus becomes chronic, secondary skin lesions can develop, including alopecia, crusting, and lichenification. However, subtle variations may occur among certain breeds.

What are your top tips to assess whether a dog is suffering from this condition?
The process is structured, following a step-by-step approach:
1. Collection of medical history
2. Exclusion of the other differentials that fit the clinical pattern
4. Application of Favrot's criteria
5. Implementation of a food elimination diet and challenge trial

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