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Allergies in Pets


Allergies are a common cause of skin and ear conditions in dogs. People with allergies usually have “hay fever” (watery eyes, runny nose, and sneezing) or asthma. However, in dogs the skin is the target organ, whether the allergen is eaten, breathed in, or in direct contact with the skin.

Allergies are managed rather than cured, which can make the treatment of allergic skin disease very frustrating. Allergies in animals, as in people, take time and effort to manage. Allergies often fluctuate with the seasons and other variations in the animal’s environment.

Allergic dogs will scratch, chew, lick their paws, rub their face, or have recurrent ear infections. The other areas most commonly affected are the armpits, lower legs, abdomen, and groin. This itchy behavior, or pruritus, can cause hair loss and reddening and thickening of the skin.


Types of Allergies, Diagnosis and Treatment

An allergy is an over-reaction of the body’s immune response to normally harmless substances.

For all types of allergies, it is very common to require a combination of treatments including medicated shampoos, corticosteroids, anti-histamines, and immunotherapy (“allergy shots”) and other immune-mediating medications. Here are the most common allergies in dogs:


Food allergy

Some humans have anaphylactic (life-threatening) reactions when they have food allergies. You likely know of someone who has to carry an epi-pen because they have a life-threatening allergy to peanuts or seafood. When dogs have food allergies they usually have chronic itchy skin or ears. With a food allergy the skin condition is usually year-round. If the skin worsens at certain times of the year it is likely that your dog also has some seasonal allergies which piggy-back on the food allergy causing a temporary worsening of symptoms.

Your dog can be allergic to the protein, carbohydrate, preservative, dye, or other substance in their food. The only method of diagnosing a food allergy is by placing your dog on a food trial: a carefully selected prescription or homemade hypoallergenic diet for 10 – 12 weeks. The diet contains only ingredients that your dog has never eaten before. If the allergy signs resolve, a food challenge is performed by feeding the former diet and watching for a return of the itching. If this occurs, a diagnosis of food allergy is confirmed. Over the counter diets may contain common food allergens, despite other label claims, and should not be used for food trials.

For food trials, as with other diet changes, a gradual transition to the new diet should occur over a few days. This will decrease the possibility of diarrhea or vomiting from a sudden diet change. Once your dog is fully on the new diet, it is imperative that the dog be fed only the hypoallergenic food and water and medications as applicable. If just one member of the family gives an occasional treat, the food trial will not be accurate.

In multi-pet households it can be difficult to feed one pet separately. For these situations a microchip automated food dispenser can be helpful.



Atopic dermatitis (Atopy) or Allergic Inhalant Dermatitis

Atopic dermatitis is a hereditary sensitivity to something that most animals would not be sensitive to such as pollen, grass, trees, house dust mites, and mold spores. Many breeds of dogs are affected as well as some mixed breeds. Even though the allergen enters via the respiratory system, a skin reaction occurs.

Diagnosis is made based on the results of intradermal skin testing or by blood testing. Evaluating the results of these tests lets you know what allergens to avoid and helps your veterinarian compile a list of allergens for a “vaccine” to decrease the pet’s sensitivity.


Secondary infections

Allergies are often the underlying cause of recurring skin and/or ear infections however because the skin is unhealthy, secondary bacterial and yeast infections can occur and complicate treatment and make your pet even itchier. Long-term treatment with antibiotics and anti-yeast medications is commonly required, along with medicated baths.


Flea allergy

Flea allergic dermatitis is the most common skin disease in dogs in most of the US and some provinces of Canada. In Alberta, fleas are not common so this possibility is least likely.


What about other animals?

Horses and cats can get asthma as well as inhalant dermatitis.  They can also get food allergies.

In horses, it can be difficult to tell the difference between allergies and reactions to insect bites.




BSAVA Manual of Canine and Feline Dermatology, 3rd ed. Gloucester: Wiley Blackwell 2012.

 Ihrke, P.J. 1995. Pruritis. In E.J. Ettinger and E.C. Feldman (eds.). Textbook of Veterinary Internal Medicine, pp. 214-219. W.B. Saunders Co., Toronto.

Scott, D.W., Miller, W.H., Griffin, C.E. 1995, Small Animal Dermatology. p. 500-518. W.B. Saunders Co., Toronto.

Wang J, Sampson HA: Food allergy: recent advances in pathophysiology and treatment. Allergy Asthma Immunol Res 2009 pp. 19-29