Allergies can affect both humans and animals. In general, most allergies are caused by environmental factors like pollen and grasses, insect bites, medications, or by certain foods. In dogs, environmental allergies are very common. Food allergies may occur on their own or concurrently with other allergies.
What Are Food Allergies in Dogs?
Allergies occur when the body's immune system identifies a substance as an invasive threat to the body that must be attacked. The immune response causes inflammation in the body.
Food allergies tend to occur suddenly in dogs after prolonged exposure to a specific ingredient in the dog food, often a protein. Most dogs that develop food allergies have been eating the same food for a long time.
Signs of Food Allergies in Dogs
Dogs with food allergies typically experience skin issues like itching, redness, rashes, raw spots, flaking, crusty lesions, and hair loss. Many dogs with food allergies will have chronic ear infections as well. Gastrointestinal problems like vomiting and diarrhea may or may not occur along with skin issues. Less commonly, GI problems may occur on their own, but this may be considered a food intolerance rather than an allergy.
Food allergies will typically first develop in puppies under six months of age or adults over age five.
Diagnosing Food Allergies in Dogs
Before diagnosing a dog with food allergies, the vet will first rule out other causes for skin problems. A full physical examination will be conducted and your vet will look for specific signs that point to food allergies.
First, the dog must be flea-free to ensure that the skin problems are not related to flea bites. This requires the use of effective flea control methods all year long. Your vet can help you find the right product for your dog.
Next, your vet may want to rule out environmental allergies by treating with antihistamine and anti-itch medications. If there are signs of skin or ear infection, your vet will likely treat your dog with antibiotics, and/or topical ear medications.
How to Treat Food Allergies in Dogs
The first step to treating a food allergy in dogs is discovering what ingredient is causing the allergic reaction. The only way to do this is by feeding a special diet to your dog over about eight to 12 weeks. Although blood testing and skin swabs for allergies are available at some labs, most veterinarians agree that these tests are not accurate enough to correctly identify food allergies in dogs.
Food Trials and Elimination Diets for Dogs
The purpose of a food trial for canine food allergies is to eliminate as many potential allergens as possible from the diet. It generally involves feeding a novel protein (something new to the dog that has never been fed before) or a diet made with hydrolyzed protein.
Your vet can help you choose a high-quality diet made with specific limited ingredients. The protein in the diet should come from one source and be either hydrolyzed or novel (a protein your dog has never eaten).
Novel Protein Diets for Dogs
These are generally composed of one uncommon protein source (like venison, kangaroo, duck, or rabbit) and one carbohydrate source along with necessary vitamins, minerals, and nutrients necessary to make the dog food complete and balanced. It's important to let your vet help you select a diet that can be trusted to only contain the listed ingredients. Special veterinary diets are often preferred over store-bought diets because they have been developed with food allergies in mind. Veterinarians trust that these diets are pure. Some commercial limited ingredient diets will contain traces of other ingredients due to cross-contamination at the processing facility.
Hydrolyzed Protein Diets for Dogs
These use proteins that have been broken down in such a way that the immune system will not recognize them as the same ingredient. For example, a dog with a chicken allergy may do well on a diet made with hydrolyzed protein.
Once a dog food has been chosen, your veterinarian will instruct you on how to conduct a proper food trial for your dog.
Food Trials Must be Strict
The most important rule of a food trial is to feed ONLY the limited ingredient diet for the time period recommended by your vet (usually eight to 12 weeks). Do not feed ANY other foods or treats unless they are made of the same exact ingredients.
Be sure everyone in your home is aware of this rule. In most cases, it's best to feed all dogs in the home the same food or separate them while eating. Make sure any other foods (like cat food and human food) are kept completely out of reach.
You may notice your dog's skin problems begin improving early in the trial period. Report these results to your vet, but do not stop or alter the food trial unless instructed to do so by your vet.
At the end of the recommended trial period, your vet will assess the outcome. If your dog showed an improvement, the vet may recommend feeding the old diet for a week or two to see if it causes signs to recur. Or, the vet may simply recommend gradually adding additional protein ingredients (one at a time for a week or two each) to your dog's diet to watch for a reaction. This can help you determine what foods your dog can and cannot tolerate.
Some dogs will need to remain on special diets for life due to food allergies. However, you may find that your dog is only allergic to one or two proteins and can eat all others without reactions. Again, work closely with your vet to choose the right dog food and manage your dog's allergies. Be sure to visit the vet for routine wellness exams every six to 12 months, or as recommended by your vet.