Is your dog scratching, biting, licking, rubbing his skin, or rolling on the ground? 

Allergic skin disease can cause significant discomfort to companion animals and is a common reason for dog owners to seek care for their pets. The cause of the itchy problem will most commonly be due to: 

• ectoparasites (usually a flea allergy); 

• food allergy; 

• bacterial infection, or 

• an environmental allergen, such as tree and grass pollens, moulds and dust mites. This condition is known as atopy.

Diagnosis

Because of the complexity of allergic skin disease, it can take several steps to reach a diagnosis and, unfortunately, in the case of atopy, these patients may need lifelong management of the condition.  

To confirm a diagnosis, your vet will need to take a detailed history of seasonal patterns, the pruritus level (how itchy), parasite prevention treatments, response to past treatments and any diet-related changes. 

They will also do some tests, such as skin smears and scrapes, skin biopsies, flea combing, and ear cytology.  

Unfortunately, blood and skin tests do not differentiate atopy from food allergy, so diagnosing atopy can be a time consuming and frustrating process, as it usually involves excluding other causes.  

Atopy can be more seasonal, while food allergy patients may also have some gastrointestinal signs. However, the best way to determine if the allergy is food-related is to run a feeding trial whereby your dog is exclusively fed a prescription protein diet. Those that respond well to this are then ‘challenged’ with their original food to confirm a diagnosis of food allergy dermatitis. 
 
If the dog is on an effective ectoparasite control and a food allergy has not been demonstrated to be involved, then atopic dermatitis is the most likely cause of the itchy condition.