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.