Does Your Dog Really Need Lamb, Bison, and Other 'Hypoallergenic' Dog Food Proteins?
By Jennifer Coates, DVM
In order to identify what is the best dog food for dogs with food allergies you must first understand what are food allergies and what causes them.
Many different terms are used to describe abnormal reactions to food. The terms “allergy” and “hypersensitivity” describe an immunologic reaction to food allergens and requires previous exposure to the allergen to bring about symptoms. In contrast, a food “intolerance” does not involve the immune system and can occur with the first exposure to a certain food. Both reactions produce similar symptoms and may be difficult to tell apart without veterinary guidance.
In fact, according to Dr. Adam Patterson, clinical assistant professor and Chief of Dermatology at the Texas A&M College of Veterinary Medicine & Biomedical Sciences Small Animal Clinic, “Food allergies in dogs present themselves quite differently than food allergies in humans. For instance, a person who is allergic to shellfish may experience throat swelling and possibly a critical or fatal reaction, but in dogs, the allergy is expressed through the skin and seen most often as itch.”
What are the Common Signs of Food Allergies in Dogs?
Symptoms of food allergies in dogs vary, but the most common complaint is non-seasonal itching that may involve the whole body or be focused on the ears and feet. Chronic or recurrent ear and skin infections are also typical. Some dogs may even develop vomiting, diarrhea, or excessive gassiness. Symptoms often begin when dogs are young (before one year of age), but may develop at any time.
What Causes Food Allergies in Dogs?
Dogs with food allergies are typically allergic to proteins, which come from animal or plant-based ingredients of the diet. The proteins are broken down into molecules that the immune system misidentifies as a potential threat. Beef, dairy, wheat, and chicken are the most common culprits of food allergies in dogs. The development of food allergies, however, takes time. So the dog may have been eating the offending ingredients for quite a long time before symptoms develop.
How is a Food Allergy Diagnosed in Dogs?
A food trial using a hypoallergenic dog food is the only reliable way to diagnose food allergies in dogs. There are two ways to do this – using a novel protein source or hydrolyzed protein.
A “novel” protein source is one that is completely new to the dog, thereby reducing the chance of an immune response. In addition, the diet should contain a novel, single source of carbohydrates since plants also contain protein. Hypoallergenic dog food options include venison and potato, duck and pea, salmon and potato or even kangaroo, as long as the dog hasn’t been exposed to these ingredients in the past. Lamb used to be considered hypoallergenic but is now in so many commercial dog foods that it is no longer novel.
Hydrolyzed diets are made when intact animal proteins are broken down into very small molecules that the immune system should not be able to recognize as allergens, virtually eliminating the possibility of an adverse food reaction. Starch or rice are typically used as carbohydrate sources because they are very infrequently associated with allergic reactions.
Whatever type of hypoallergenic dog food is used, it should be fed for a minimum of 8-10 weeks to adequately assess the dog’s response. Most dogs experience at least a partial improvement in their food allergy symptoms within the first 4-6 weeks, but several dog breeds (including Labrador Retrievers and Cocker Spaniels) may require a longer period of time to respond. It is important to feed only the hypoallergenic dog food, avoiding all other foods, treats and even flavored medications such as chewable heartworm preventives, antibiotics, and pain relievers.
Once the food allergy has been diagnosed using a hypoallergenic dog food, a challenge should be performed to confirm the diagnosis. When the original diet is fed, the symptoms should return within two weeks. Following confirmation of the food allergy, single source ingredients (e.g., slices of chicken or a sprinkling of wheat) may be added to the hypoallergenic dog food to determine exactly which ingredients must be avoided in the future.
What is the Best Food for Dogs with Allergies?
It is important to work with a veterinarian to determine the best food for dogs with allergies. Novel protein and hydrolyzed diets that are available by prescription only are superior to those that can be bought over the counter because the latter often contain trace amounts (or more) of common allergens, even if they are not listed on the label. Randomly eliminating ingredients from your dog's diet without the input of a veterinary nutritionist is also a bad idea, as it can result in nutritional imbalances and is unlikely to identify the underlying problem.
Save yourself the worry and speak with your veterinarian if you suspect that your dog has a food allergy.
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Patterson, A. Itchy Dogs: Is Food the Problem? Texas A&M University, Veterinary Medicine and Biomedical Sciences. Accessed February 3, 2014.
Thomas, R.C. Food Allergy in Dogs & Cats. Presented at the 2005 Western Veterinary Conference, Las Vegas, NV.