Not all itchy skin and scratching is due to allergies and unfortunately there is no test that actually diagnoses allergy in pets.

Rather, your vet will perform an allergy work-up that will exclude all other possible causes and interpret your pet's health history.

In order to diagnose allergy, your vet will use a process of elimination to exclude other causes of your pet's symptoms. There are other things that can cause symptoms similar to allergy, such as fleas, scabies, infections, drug reactions etc, as well as other diseases not related to allergy.

Step 1: Rule out fleas 

Step 2: Rule out other parasites 

Step 3: Rule out infection 

Step 4: Rule out food allergy 

Step 5: Look at history & clinical signs

Fleas and flea allergy can cause similar symptoms to skin allergy including itching and infection, therefore it is important to ensure fleas are not the cause of your pet's allergy-like symptoms. 

Eliminating fleas as a possible cause is fairly easy simply by ensuring your pet's flea treatments are done regularly.

If fleas have been ruled out, your vet can perform some tests to rule out other parasites such as demodex and other mites.

If one of the symptoms your pet is suffering from is a skin +/or ear infection, your vet will treat this with appropriate treatment. 

If the infection recurs, then it is likely to be associated with an underlying allergy.

If the allergy symptoms remain after excluding or treating other causes so far, the next step is to exclude the possibility of food allergy. 

The only way to prove food allergy is by doing a food trial, whereby you feed your pet a novel diet for a minimum of 8 weeks. Your vet may choose to run a test that can help identify which ingredients may be appropriate for a food trial. It is important to remember though that this does does not prove what food your pet is allergic to. 

For more detailed information of food allergy, food allergy testing and diet trials:

After all previous steps have been taken, by looking at your pet's health history eg when did the symptoms start, how severe are they, when do they occur and location of symptoms etc, your vet will conclusively be able to diagnose allergy.

Once the allergy work-up has been conducted, your vet can run an allergy test to help determine the allergens that your pet is sensitive to. 

Visit our section on allergy testing to read more on what this involves.