Introduction

Canine atopy can be difficult to distinguish from flea bite allergies, sarcoptic mange (scabies), demodectic mange (demodicosis), food allergies and other skin and hair-loss disorders, making it somewhat difficult to diagnose. However, the dog’s history, physical examination results, location of affected skin areas (lesions) and possible seasonality of symptoms can all lead to a suspected diagnosis of atopic dermatitis. Further tests can definitively diagnose the disorder.

How Atopy is Diagnosed

A dog that presents with pruritis (itching and scratching) and other signs of skin discomfort and disease will go through a thorough physical examination, including a dermatologic examination, at the veterinary clinic. Additional diagnostic tools include deep skin scrapings, microscopic analysis of plucked hairs (trichography), bacterial and fungal cultures, skin fine needle aspirate or biopsy with corresponding cytologic and histopathic examination of the skin samples, and dietary modification. Flea allergies, food allergies and adverse reactions to other external parasites must be ruled out to definitively diagnose atopy, because these conditions can complicate the diagnostic and treatment decision-making process. Bacterial, fungal and other skin infections, as well as cancer and behavioral disorders, must also be ruled out.

The most reliable form of advanced confirmatory testing is intradermal skin testing, which is very similar to the process used to diagnose specific allergies in people.

This is the gold standard for diagnosing environmental hypersensitivities, and should only be conducted after oral or injectable drug therapy has been stopped for an appropriate period of time, ranging from weeks to months. The veterinarian will inject directly under the patient’s skin tiny amounts of substances known to commonly cause skin allergies in domestic dogs. After a certain period of time, she will evaluate the injection sites for any observable abnormal reactions. The process can be time consuming and costly. It can also be uncomfortable and even painful for the patient, as human patients can attest.

If intradermal testing is unavailable or impractical in a given case, there are several serum tests available to help the veterinarian identify possible causative allergens by identifying antibodies to those allergens in the dog’s blood. These tests are more convenient, less expensive and less risky than intradermal skin tests. They also are less reliable in terms of their results.

Special Notes

Canine atopic dermatitis is one of the most frequent and frustrating skin diseases in companion dogs, for the owner, the veterinary team and the pet. However, with time and patience, it usually can be manageable for all involved.