Dog Allergies: Common, Commonly Misdiagnosed, or Both?

by Jennifer Coates, DVM

Watching an itchy pet scratch to the point of self-mutilation is an agonizing and all-too-common experience for dog owners.

The veterinary visits that usually (and should!) follow often result in a diagnosis of allergies.

While allergies are extremely common in dogs, owners should be aware that this very fact can sometimes lead vets to diagnose an allergy when something else is to blame for a dog’s symptoms.

First, an overview of allergies.

Dogs can be allergic to almost anything in their environment:  ingredients in food, flea bites, pollen, mold spores, dust mites, etc.  The topic of food allergy has been elegantly discussed by Dr. Schaible so I won’t go into it here, other than to say that every dog with non-seasonal itchiness needs to be assessed for a food allergy.

The importance of flea allergies also cannot be overstated.  

A flea allergic dog can be driven to desperation by the bites of only one or two fleas. Owners often give their dogs a once-over, don’t see any fleas, and discount the little buggers as a cause for their pet’s itching.

But, EVERY itchy dog needs to be on an effective flea preventative medication all year long.  

The good news is that many of these products also kill other parasites that cause itching in dogs (e.g., Sarcoptes mites, lice, etc.) so owners get a lot of bang for their buck.

Back to what most people think of as typical allergies – the pollens, molds, etc.  

These are often called inhalant allergies, but this is a bit of a misnomer. Unlike people who typically develop runny and itchy eyes, sneezing, etc. after inhaling allergens, the cells responsible for these reactions occur primarily in a dog’s skin, which explains why dogs are itchy rather than sneezy when suffering from allergies.

The correct term for the genetic predisposition to this type of allergic reaction in dogs is “atopy.”

What does this mean for dog owners?

Perhaps most obviously, if your dog has chronic respiratory symptoms (e.g., a runny nose, sneezing, coughing, etc.) the most likely diagnosis is NOT allergies.  

If, however, your dog is itchy, atopy will be towards the top of a vet’s list of potential causes.  As tempting as it may be (especially in the middle of a busy day in the clinic or when faced with a client complaining about prices), a vet shouldn’t rush into an allergy diagnosis but, first, rule out some of the other common causes of itching including:

• a thorough physical exam looking for fleas, lice, and other obvious causes of a dog’s symptoms,
• a skin scraping for mange mites,
• a fungal culture to rule out ringworm,
• skin cytology to diagnose bacterial and fungal skin infections,
• and sometimes empirical treatment for some of the harder to diagnose “itchy” diseases (e.g., sarcoptic mange).  

Only after all this is a TENTATIVE diagnosis of atopy appropriate.

Why do I say “tentative?” Because all of the potential causes of canine itching have not yet been ruled out, and atopy is a diagnosis of exclusion.

Definitively diagnosing allergies and identifying a dog’s triggers can involve such things as skin biopsies and intradermal skin tests, and these advanced diagnostics are not called for in every case.  

It is appropriate to begin treating most dogs for allergies without these tests, as long as everyone understands that if the pet does not respond to treatment, the initial diagnosis should be reevaluated.

An allergic dog’s symptoms should quickly get MUCH better with aggressive treatment.  

This often consists of medications to control the allergic response (corticosteroids and cyclosporine are typical examples), weekly baths using an appropriate, medicated shampoo, and nutritional supplements like omega 3 fatty acids.

Keep in mind that your dog’s symptoms will probably recur if you stop treating him, but if you are concerned that he was misdiagnosed in the first place, talk to your veterinarian or seek a second opinion, ideally with a veterinary dermatologist.

***

Jennifer Coates, DVM graduated with honors from the Virginia-Maryland Regional College of Veterinary Medicine in 1999.  In the years since, she has practiced veterinary medicine in Virginia, Wyoming, and Colorado.  She is the author of several books about veterinary medicine and animal care, including the Dictionary of Veterinary Terms: Vet-speak Deciphered for the Non-veterinarian. 

Jennifer also writes short stories that focus on the strength and importance of the human-animal bond and freelance articles relating to a variety of animal care and veterinary topics.  Dr. Coates lives in Fort Collins, Colorado with her husband, daughter, and pets.

Related articles:
Why Is My Dog So Itchy? Top 5 Causes Of Itching In Dogs
Food Allergies in Dogs

Articles by Dr. Coates:
The Perplexities of Pancreatitis
The Other Side Of The Coin: The Cost Of Defensive Medicine
To Neuter Or Not To Neuter… That Is The Question
Don’t Forget the Physical Therapy
Common Misdiagnoses (Part 1)
Common Misdiagnoses (Part 2)
Picking the Right Dog to Breed
When Is It An Emergency?