How itchy is your dog, really?

By Jon Plant, DVM, DACVD

Scratching, biting, chewing, rubbing, and excessive licking can all be signs of itch in dogs. A number of methods have been developed to try to quantify itching, but these are most useful in research settings.  One method is to take videos of kenneled dogs then track all itching behavior seen over a period of time.  Another idea that I have published research itchy-dogon is the use of sophisticated motion sensors attached to dogs’ collars. The most widely used method is to ask the dog’s guardian to rate the level of itch severity on a linear scale.

Why might measuring itch be important, you ask? I think of it like this: would you start a weight loss program without knowing how much you weigh? Excessive itching has a negative impact on dogs’ quality of life.  Surprisingly, most veterinary medical record standards do not require us to record itch severity. A meaningful measure of itch severity that you could share with your veterinarian would be a great step forward in helping pet owners help their itchy dogs.

Food allergy in dogs

This month I will discuss food allergy in dogs.  This first installment will describe how frequently food allergy is diagnosed in dogs with itchy skin.  In coming weeks, I will cover the clinical signs of food allergy, diagnosing food allergy, and feeding home prepared and/or raw diets versus commercial diets.

Food allergy, also known as food hypersensitivity or adverse food reaction, can result in skin or gastrointestinal conditions, or both in the same dog.  An allergy is an exaggerated immune response to a substance that most dogs tolerate without problem.  Food allergy may develop for the first time during puppyhood, or as an adult.  Most often they are young adults when signs first begin. Dogs may have eaten a food ingredient for years before developing an allergy to it.

The global pet food industry is a big, competitive business. It is expected to exceed $50 billion by 2015.  It is not surprising that more than 500 new foods are introduced every year to try and capture a share of the market.  Nor is it surprising that they are able to shape consumers’ perception of a condition like food allergy with their large marketing budgets.  According to an FDA web site “this [hypoallergenic] marketing niche was detrimental in two respects. The true nature and incidence of food allergies was clearly overemphasized and misrepresented.”

Walking through the aisles at your local pet store, you would think that every other dog must have a food allergy.  Claims like “hypoallergenic” and “natural” are found on nearly every bag or can of food.   What do these terms mean?  A food can be labeled “natural” if its ingredients are from animal or plant origin, or are mined.  They can still be labeled natural if ingredients are extracted, hydrolyzed, or fermented.  They may also contain synthetic nutrients and still be labeled as natural.

The true prevalence of food allergy in dogs is unknown, but it is almost certainly lower than many pet food companies would have you believe.  Based on a variety of studies, estimates of the prevalence of food allergy range from 9% to 36% of dogs with allergic skin disease. This probably translates to about 1-3% of all dogs.  Atopic dermatitis due to environmental allergens is much more common.  The majority of itchy dogs do not respond to strict diet changes, although it can be an important diagnostic step to take.  In the coming weeks, I’ll discuss the signs of food allergy and how to make an accurate diagnosis.