Dog News

Allergies in Dogs

by Shawn Finch, DVM

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Joy the Puppy Scratching an Itch

The most common sign of allergies in dog is itchiness.

Pretty simple, huh?


If your dog itches, he or she could have any one of countless conditions, including allergies…to just about anything.  Allergies cause itchiness, but itchiness does not invariably signal an allergy problem.

My Dog Does Itch! Now What?

Work with your veterinary team to rule out non-allergy causes of itching.

Get rid of allergy complicators. Often allergic conditions will cause secondary conditions, most often otitis (ear inflammation) and dermatitis (skin inflammation), which also need to be treated while the allergies are being diagnosed and treated.

Keep your dog comfortable. I do not want to be one of those Ask-your-doctor-if-WonderDrug-is-right-for-you types, but I will say that your veterinary team has all sorts of options available to relieve your dog’s itchiness, including steroids, antihistamines, immune modulators, omega 3 fatty acids, shampoos, conditioners and sprays.

Downsides to symptomatic treatment (treating the symptoms instead of the underlying cause):

  • Some medications will interfere with some diagnostic tests.
  • Masking symptoms may make allergy diagnosis and treatment more difficult.
  • All medications have potential side effects.  Long term use increases risks.  (Yeah steroids, I am looking at you!)

Whenever possible, identifying and dealing with the allergy itself, through direct treatment or avoidance, is ideal.

Bringing Order Out of Chaos – Allergy Diagnosis and Treatment

Dogs are generally allergic to one of three things:  fleas, environmental allergens or food protein.

Flea Allergies

If you and your veterinarian suspect allergies, start your pet on a flea preventative/treatment if one is not already in place.  Whereas most dogs need a pretty impressive number of fleas on board to cause discomfort, a dog who is allergic to fleas becomes almost unbearably itchy after even a single flea bite.  You may not even see any fleas. If signs abate with flea prophylaxis, look no further!  You and your veterinary team have just diagnosed and treated allergies in such a way that your dog never has to suffer from allergies again!  VERY rare scenario in the world of pet allergies!

Environmental Allergies

Environmental allergies are diagnosed with serum testing or intradermal skin testing.  Either can be tailored to specific allergens in your pet’s environment.  Usually complete allergen avoidance is not possible (“You may come in contact with these pollens, but not those…”), and immunotherapy based on test results is initiated.

Very small doses of the offending allergens are prepared in injectable form.  The veterinary team administers the treatment in a decreasing dose and increasing interval over a span of several months.  Pet owners can take over treatment if they are comfortable doing so.  Most dogs experience some relief, and some are completely freed of allergy symptoms with immunotherapy.  Downsides include the long course of treatment and the unpredictability regarding which dogs will respond and to what degree.

Food Allergies

The only accurate way to diagnose food allergies is with a strict, several week long food trial.  Choices of food for the trial include:

  • Novel protein prescription diet (a diet containing a single protein, which hopefully your pet has not been exposed to in the past, for example, Royal Canin Venison and Potato diet)
  • Hydrolyzed protein prescription diet (a diet in which proteins in the food are “hydrolyzed” – broken down enough to not be recognized by the immune system, for example, Science Diet z/d)
  • Limited ingredient homemade diet concocted by you and your veterinary team

Generally food trials will be between six and twelve weeks long.  The biggest drawback to a food trial is that NO other foods may be given during this time.  Easy for me to say, very difficult to do in Real Life!

If improvement of symptoms is seen, the food trial is complete, and a diagnosis of food allergy is achieved.  Next, simple proteins (chicken, beef, etc.) are introduced back into the diet one at a time.  If signs reappear, not only do we have a food allergy diagnosis, we also have a specific diagnosis.  From that point forward, treatment consists of avoiding any food and treats containing the offending allergen(s).


Allergies are rarely completely cured, but can almost always be controlled.  Achieving allergy diagnosis and optimal treatment will take time, sometimes several months or even a few years of cycles through the seasons.  Our goal is comfort. If your dog is usually not itchy and almost never has major skin or ear issues secondary to allergies, we have succeeded.