Food ‘Allergy’ and Food ‘Sensitivity‘ Basics

“Dog Scratching” by anankkml

Many of our pets suffer from food allergies, food insensitivities, or food intolerance.  Signs of these conditions can range from an immediate reaction like hives or difficulty breathing to delayed reactions, such as chronic gastrointestinal problems (irritable bowel, excess gas), itchiness, and chronic skin, ear, and foot infections. Recognizing that these conditions are related to your pet’s diet, identifying the food(s) to which your pet is reacting, and eliminating the offending food can be challenging, but help is available!

Food allergies and food sensitivities (or intolerance) are two very different things, with sensitivities being far more common. In fact, it is actually uncommon for pets to exhibit true food allergies. Symptoms of food allergy appear almost immediately after the offending food is eaten. An example is peanut allergy, in which individuals allergic to peanuts experience an immediate reaction, which may range from rashes, hives, swollen eyes or lips, to a more serious reaction, such as difficulty breathing and reduced blood pressure (anaphylactic shock).  Allergic reactions are associated with elevations in specific body proteins or immunoglobulins (Ig), called IgE and IgG.

Dog scratching

In contrast, food sensitivity often results in chronic conditions, most often affecting the skin and gastrointestinal tract. Food sensitivity may not be evident the first time the offending food is eaten. It may take months or years before it is seen. Food sensitivity reactions are associated with elevations in IgA and IgM.

The difference in the immunoglobulins affected can be used to differentiate between food allergy and food sensitivity and to identify the specific food to which the pet is reacting.

Dr. Jean Dodds has developed a method, called NutriScan, to identify food allergies and sensitivities in dogs and cats (available at NutriScan tests the 24 most commonly ingested foods in cats and dogs using saliva. Foods tested are: beef, corn, wheat, soy, cow’s milk, lamb, venison/deer, chicken, turkey, white fish, pork, duck, chicken eggs, barley, millet, oatmeal, salmon, rabbit, rice, quinoa, potato, peanut/peanut butter, sweet potato, and lentil.

Dr. Dodds suggests that NutriScan testing be done at puberty or older, however dogs with clinical symptoms suggestive of food sensitivity may be tested as young as 6 months. Dr. Dodds and her team review the results of the Nutriscan test and recommend which food(s), if any, your dog should avoid.  Following elimination of the offending food, improvement can take from days to several weeks, as each case is individual. Ideally, dogs with suspected or established food sensitivities should be retested every 12 to 24 months to make sure new sensitivities have not developed.

While it may seem simple, eliminating the food to which your dog is sensitive can actually be quite challenging. I’ll use chicken as an example, but the following applies to any protein. Your chicken-sensitive pet may react not only to eating chicken but to eating another protein source that was fed chicken prior to being made into pet food. In fact, many commercial dog foods formulated to be fed to dogs with food intolerance have been found to contain proteins that are not listed on the label. In a study evaluating the content of 12 canine limited-ingredient dog foods, ten contained at least one protein from sources not listed on the label! (Source, Ricci et al. Identification of undeclared sources of animal origin in canine dry foods used in dietary elimination trials. J An Physiol An Nutr. 2013;97 (suppl 1):32-28.) Numerous other studies also document discrepancies between the labeled content and actual content of dog and cat food (for more information see: This means that a dog or cat food that does not list chicken on the label may actually contain chicken! It is no surprise then that chicken sensitive pets fed this food would continue to demonstrate signs of sensitivity!

This can make managing dogs with food sensitivities challenging, as it can be nearly impossible to be certain you are eliminating the offending food. For that reason, we suggest that dogs who do not respond to a commercial elimination diet (i.e., a commercial diet whose label does not list the food to which there is sensitivity) be fed a homemade diet consisting of a novel protein so that the content can be better controlled.

We have one final important point to share. It is not uncommon for me to hear someone say their pet is ‘allergic to poultry.’ Interestingly, using NutriScan testing, Dr. Dodds has shown that pets sensitive to one type of poultry are not necessarily sensitive to all types of poultry. So, for example, if your dog is sensitive to chicken, he or she may not be sensitive to duck. Therefore, it may not be wise to make assumptions about classes of foods to which your pet is sensitive, but instead to test to confirm specific foods that should be avoided.

More information is available at Dr. Jean Dodd’s Pet Health Resource Blog. and


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