The ACVD task force on canine atopic dermatitis (XV): fundamental concepts in clinical diagnosis.

The clinical signs of atopic dermatitis (AD) in man and in dogs are variable, and there is no single physical or historical feature that, if present, indicates the presence of AD. The initial diagnosis of AD is made clinically with the fulfillment of a combination of criteria that are strongly associated with the disease. Several schemes have been proposed in an attempt to define uniform clinical criteria for diagnosing canine AD, but no system is perfect. Once AD is considered as a possible diagnosis, other important differential diagnoses must be methodically eliminated from consideration. As a final step, once the clinician is certain that AD is probable, "allergy" tests may be conducted to provide additional evidence to "substantiate" the diagnosis. It is important to understand that allergy testing, in whatever form, is not appropriately used early in the patient evaluation as a screening test. Rather, it should be reserved, after a firm clinical diagnosis of AD has been made, to implement allergen avoidance schemes or to select allergens to be incorporated in immunotherapy formulations.