Disclaimer: Contact your veterinarian if you have questions or concerns about your dog.
Allergies in dogs can have multiple causes. Environmental allergies (think pollen, dust, etc.) are very common, especially in the southeastern U.S. Fleas can also be very problematic in this area and just a single bite from a flea can trigger severe symptoms that can last for weeks in allergic dogs. Another type of allergies in dogs is food allergies. Food allergies are reportedly less common than environmental and flea allergies, but the true incidence is not known. Further clouding the issue is that dogs with one type of allergy (environmental, for example) often have other allergies too. This means that even if you fix one of the causes of their allergies, the symptoms may not COMPLETELY go away. I will focus on food allergies for this post.
Food allergies cause symptoms including itching, licking/chewing feet, rubbing the face/muzzle, anal gland issues, and can be a significant cause of ear infections. These symptoms are typically year-round, which is the first clue that a dog may have food allergies, though environmental allergies can cause symptoms year-round too. Gastrointestinal symptoms, such as vomiting and diarrhea CAN occur, but are not the main signs that occur. Many people mistakenly think that “grains” are the main cause of food allergies in dogs. This is almost never the case (not “grains” as a general group anyway). There are certainly dogs that are allergic to a particular grain or a few grains; however, most dogs are allergic to the common proteins in pet food. The most commonly reported are beef, soy, and chicken, but dogs can be allergic to any protein in their food.
Diagnosing a food allergy can be a challenge. There are blood tests that claim to be able to diagnose food allergies; however, they are not considered by many veterinary dermatologists to be accurate. Unfortunately, the only way to definitively diagnose a food allergy in a dog is to do a “food trial”, otherwise known as a “dietary elimination trial.”
Food trials entail changing a dog’s food to a protein and carbohydrate that he or she, ideally, has never been exposed to or at the very least has not been eating recently. This means if a dog was eating a food that had chicken and corn, or beef and rice, we would want to switch to a food that did not contain those ingredients (think rabbit, venison, turkey, salmon, etc.). However, one must really look at the ingredients on a food label, because some foods are labeled as a chicken recipe or a beef recipe and also contain other protein sources such as fish, turkey, etc. The food should be selected with the assistance of your veterinarian. Once a food is selected, you must only feed THAT food with treats only being allowed to contain those ingredients as well. This is where many people fail at food trails. If other foods/treats are fed, the food trial will often not work. Food trials usually take 6-8 weeks to fully evaluate response. The response may not be complete resolution of symptoms because, as I stated above, many dogs have multiple types of allergies.
If a positive response (reduction/elimination of symptoms) is achieved with a food trial, many people simply stick with the food that fixed the problem and just assume that their dog is allergic to something in the old food. That’s understandable. But to PROVE that a dog is allergic to a certain ingredient (and to determine which ingredient is the issue), you need to do a “challenge” and “recovery.” The “challenge” part entails feeding ingredients from a previous food or feeding the previous food for a few days to a few weeks and observing to see if signs of allergies return. If they do, you then switch back to the food that was used for the food trial and “recover” them. This process confirms food allergies and can allow you to switch to a different food from the one used on the trial (if desired).
I have recent personal experience with this whole process because my Owen, who has allergies, showed signs suggestive that some of his allergies were food related (anal gland issues, ear issues, muzzle/face rubbing, excessive paw chewing/licking). I did a food trial; his symptoms improved; and I have challenged him with the ingredient that I thought was likely the problem. I am now at the “recovery” stage and have confirmed that Owen is allergic to fish (in addition to his already known wheat allergy). Owen’s allergy symptoms did not FULLY go away on a food trial, but I know that he also has environmental allergies, so I wasn’t surprised about that.
As always, contact your veterinarian if you have any concerns about your dog.