An allergy is a condition of unusual sensitivity to a substance or substances usually protein in nature which is perceived by the body as foreign. Signs of allergies in dogs may manifest as itching and in some cases diarrhea. Food allergies account for only about 5 to 10 percent of all allergic reactions in dogs. Diagnosis of a food allergy is a demanding diagnostic process requiring strict dietary management to make sure no allergy-triggering food is ingested by your dog.
Because the signs of food allergy resemble those of other canine allergies – and because effective treatment depends on pinpointing the allergy-causing ingredient – diagnosing food allergies is challenging for both owners and veterinarians. If your dog has an immediate adverse reaction to a diet change, the reaction is probably not an allergy because it takes more than one exposure to a food ingredient to incite an allergic reaction. That’s why dogs that have been eating the same food for months or years with no problem can develop a food allergy.
The most common sign of food allergy is inflamed, itchy skin, usually around a dog’s feet, face, ears, armpits, and groin. The scratching and biting can lead to secondary bacterial skin infections and ear canal infections.
Some food-allergic dogs experience vomiting and diarrhea instead of – or along with – skin problems. Over the last 10 years in our practice, with the advent of endoscopy ( a fiber optic tube placed down into the stomach and intestine of animals), we have diagnosed food allergy as a component of vomiting and diarrhea. It is now felt, that food allergy is the primary component in certain cases of inflammatory bowel disease. By simply changing the diet to a hypoallergenic diet , which we will discuss later, and the intermittent use of corticosteroids, we have successfully treated this disease.
If you bring your dog to the animal hospital with a complaint of itching or digestive distress, your veterinarian will first rule out more common causes of these signs. The rule-out process might include a physical examination and laboratory tests for flea allergy dermatitis, the most common cause of allergic skin disease of dogs, inhalant allergies, seasonal reactions to pollen, mold spores, and dust mites, and food caused digestive intolerance, an acute adverse reaction to food that does not involve the immune system.
If the food allergy remains a suspect, your veterinarian will then help you try to pinpoint what might be causing your dog’s problems. Most food-allergic dogs are hypersensitive to only one or two ingredients, with beef and dairy proteins topping the culprit list. Ingredients that may also cause problems – but not as often – include grains, pork, chicken, eggs, and fish. Allergies to food additives including preservatives may also be a cause but are rare.
To definitely diagnose food allergies, most veterinarians recommend a trial with an elimination diet – a diet that contains a protein and carbohydrate source the dog has never been exposed to.
To start with, feed the elimination diet for a period of up to 16 weeks and monitor your dog’s response. Signs should abate if your dog is indeed food-allergic. Keep in mind that it’s difficult to find elimination diets in spite of the plethora of grocery- and pet-store offerings because most such foods contain similar ingredients. Even the so-called “hypoallergenic” lamb-and-rice diets are unsuitable as elimination diets for many dogs because they’re so popular the main ingredients are no longer truly novel. Consequently, to carry out a valid elimination-diet trial, you may have to either buy a therapeutic diet from your veterinarian (which contains “exotic” ingredients such as rabbit, venison, and potato) or some of the newer “novel protein” diets that contain a totally and nutritionally sound newly formulated protein or prepare a home-cooked diet. Some of the manufacturers are working diligently to develop these new hypoallergenic diets.
Unfortunately in an attempt to capitalize on the use of lamb as a health food, food manufacturers and retailers sold a bill of goods to caring dog owners. It really is no more nutritious than any other form of meat or poultry. This particular product was used purely as an “elimination” diet by veterinary dermatologists to diagnose food allergies. As a result, we as a profession lost a readily available source of food for allergy testing. Now we are using rabbits, and venison (deer) as a source of hypoallergenic foods.
To get conclusive results from the trial, your dog should ingest nothing but the elimination diet and water. That means no treats, rawhide, or chewable medications. Following this strict regimen can be difficult, especially for those living in multidog households.
If signs are resolved after an elimination-diet trial, you can assume something in your pet’s diet is causing the allergy. But to be certain, some veterinarians recommend reintroducing the original diet. A recurrence of signs within 7 to 14 days confirms food allergy.
There is no cure for food allergies. Managing a food allergy means simply avoiding the causative ingredient or ingredients. Medications (such as antihistamines and corticosteroids) that reduce itching caused by other types of allergies usually don’t work on food-induced itching.
Long-term avoidance is simply a matter of keeping your dog on the elimination diet you used to diagnose the allergy. Unfortunately, however, some dogs become allergic to ingredients in the elimination diet over time. If this happens to your dog, you’ll need to find another nutritionally balanced diet that contains “new” proteins and carbohydrates.
Although diagnosing and managing food allergies is challenging, remember – most dogs are not food-allergic. So don’t automatically think food if your pet has skin or digestive problems.
Whether you’re diagnosing a canine food allergy for the first time or managing an ongoing case, you’ll need to find an elimination diet that contains a protein and carbohydrate source your dog has never eaten before. Often, the choice boils down to either a commercial therapeutic diet from your veterinarian or home-prepared food. Each has its pros and cons.
Dry or canned commercial diets are convenient, nutritionally balanced, and palatable. However, studies show that a small percentage of food-allergic dogs react adversely to commercial elimination diets that contain the some basic ingredients as homemade diets that do not cause a reaction. Experts surmise that manufacturing processes may increase the allergenic properties of certain ingredients.
Two-ingredient homemade diets (such as chicken and rice) are acceptable for the duration of a diagnostic food trial, but they are not nutritionally complete. Concocting a nutritionally balanced homemade diet for long-term feeding requires the aid of a veterinary nutritionist, a lot of time and expense, and the addition of nutritional supplements that may themselves contain allergy-provoking proteins. Thus, many veterinarians recommend starting with a commercial elimination diet and resorting to a home-cooked approach only if your dog doesn’t respond favorably to the commercial food.
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