Atopic Dermatitis in Dogs: A Clinical Syndrome by Many Triggers
Much progress has been done in the past decades on our understanding of this complex syndrome. Currently, the term canine AD is used to define a clinical disease that is associated with characteristic clinical signs and the presence of allergen specific IgE . Based on the clinical experience of a variable clinical response when targeted treatments are used, it is increasingly clear that different pathways may achieve clinical signs of AD. Thus, AD is not to be viewed as a single entity, but more as the descriptive term for a clinical syndrome.
Currently, in veterinary medicine, the term AD is frequently used as synonymous as environmental allergic skin disease and the presence of allergen-specific IgE are considered one of the criteria for clinical diagnosis of AD. The term atopic-like dermatitis (or intrinsic AD) is reserved for dogs that have clinical signs of AD, but no detectable allergen-specific IgE. It is unclear whether this presentation represents the early stage of AD or a different subtype of this syndrome. Clinically, the classic atopic dogs and the atopic-like dog are indistinguishable, creating a potential additional challenge for the clinician in terms of therapy. Currently, we do not know if this subtype of dogs are less responsive to drugs used for the management of pruritus, but we do know that they are not amenable to allergen-specific immunotherapy since we cannot demonstrate an allergenic trigger for their disease.
In the past, in veterinary medicine, the term AD was used when the allergic trigger was environmental allergens. Currently, we have increased awareness that food driven skin disease may look indistinguishable from the one triggered by pollen or other environmental allergens. Thus, the traditional separation between “food allergy” and AD is no longer an appropriate one. AD is a clinical diagnosis and does not refer to the nature of the allergenic trigger. It is also important to point out that food-induced dermatitis may manifest in a multitude of ways and that AD is only one of the possible manifestations. Others may include, but are not limited to, urticarial plaques or vasculitis.