Food Allergies in Dogs

Definition of Food Allergies

Food allergies, also referred to as food hypersensitivities or adverse food reactions, are abnormal immune responses to something in a dog’s diet. Some common causes of food allergies in dogs are beef, pork, fish, lamb, chicken, dairy products, grains, potatoes, eggs, soy products and a variety of different dietary supplements. 

Poorly digestible proteins also can cause food allergies. When the immune system senses that something is foreign, it remembers the offending substance and tries to get rid of it every time it comes into contact with it. Dogs with food allergies are very itchy. They scratch, have raised skin bumps and lose their hair. Some vomit and develop diarrhea. 

Food allergies typically show up in young dogs less than one year of age. Fortunately, they usually are manageable. Treatment requires plenty of time, money, dedication and patience on the part of the dog’s owner.

Causes and Prevention of Food Allergies in Dogs

Causes of Canine Food Allergies

Canine allergies of any sort, including allergies to ingredients in food, are caused by an abnormally strong response by the immune system to something that the dog has come into contact with more than once, either by ingestion (eating it), touch, smell or inhalation. The things that trigger allergic reactions are called allergens.

In a nutshell, when the immune system perceives something as being foreign and therefore potentially dangerous, it initiates a cascade of events on a cellular level designed to identify and get rid of the intruder. Certain immune cells develop a finely-tuned memory of the foreign substance. 

When the dog comes into contact with that substance a second time, the memory cells are primed to react faster than they did the first time. Subsequent exposures to the allergen make the immune system’s reaction increasingly sensitive, specific and swift. This is why allergies are also referred to as hypersensitivity reactions.
Different allergens can trigger different allergic reactions in different dogs. Any of the components of dog food, whether commercial or homemade, canned or in kibble form, can cause an allergic reaction. 

Some of the food products that commonly cause allergies in domestic dogs are beef, pork, fish, lamb, chicken, milk and dairy products, wheat and grains, potatoes, eggs, soy products and a variety of different dietary supplements. Poorly digestible dietary proteins are also common causes of canine food allergies. 

It can take a long time and a great deal of patience to identify the precise food ingredient or ingredients that are causing the symptoms in a dog with food allergies. Nonetheless, the process is worthwhile and almost always successful. The most effective way to determine the cause of a dog’s allergic reaction to something in its diet is to put it on what is called an “elimination diet.” This involves taking away the dog’s access to any food products other than one or two specific bland ingredients, such as boiled rice and chicken, and then gradually introducing other ingredients to the diet one at a time. 

Over the course of the elimination diet, the owner and veterinarian will track the dog’s reaction, if any, to each new ingredient. Hopefully, the ingredient or ingredients that were causing the allergic reaction will eventually be identified. 
Preventing Food Allergies
Once specific food allergens are identified, the dog’s owner will need to carefully manage the dog’s diet, to be sure that those offending ingredients are not included in its food. Fortunately, there are a number of high-quality commercial diets that contain novel protein sources, such as venison, bison, rabbit, duck, and salmon.

These often work very well for dogs with allergies to the more common components of commercial canine kibbles, which usually are chicken, beef or lamb. Tasty kibbles with one or more novel proteins are becoming increasingly available at retail pet food outlets. They can really help dogs that are suffering from food allergies regain and maintain their good quality of life.

Diagnosing Food Allergies in Dogs

Initial Evaluation
Dogs with food allergies usually are taken to a veterinary clinic with a history of intense licking, scratching and biting at random areas of their skin. They also often have visible skin sores, redness, and patchy hair loss. These signs are fairly non-specific and are more commonly caused by flea bite hypersensitivity or by some sort of inhalant allergic reaction, similar to seasonal hay fever.

The veterinarian will take a detailed history from the dog’s owner, paying particular attention to when the symptoms started, what the dog is fed and whether there have been any recent dietary changes. She will perform a thorough physical examination, keeping a lookout for any evidence of fleas or other external parasites.

Diagnostic Procedures

If the veterinarian doesn’t find fleas, flea dirt (flea fecal material) or any other obvious source of the dog’s discomfort, she may suspect that the dog is allergic to something it is eating or coming into contact within its immediate living environment. 

If the facts point to a food allergy, the doctor may recommend an elimination diet, which is the best way to identify the exact food ingredient or ingredients that trigger a dog’s food allergy. Any ingredient in commercial or homemade diets can cause an allergic reaction, depending on the particular dog’s immunological make-up. 

Feeding an elimination diet can be frustrating, and it can take a long time to figure out exactly what the dog is allergic to. The elimination diet protocol involves taking all commercial foods away from the dog and feeding it only one or two simple, identifiable ingredients at first – usually starting with boiled rice and chicken made from grocery store human-quality ingredients. 

The owner will have to watch his dog carefully to see whether its symptoms improve on this diet. If they do, he will be instructed to add only one additional item to its meals, maybe beef, lamb or corn. If the itchiness still doesn’t recur, then the dog isn’t allergic to any of those ingredients. One by one, additional foods will be added to its meals, until the itching, scratching and other symptoms return and the culprit is identified.
Dogs can be allergic to more than one component of their diet. The owner must be religious about keeping his dog away from table scraps and access to any other ingestible items during an elimination diet. All treats should be withheld. 

The foods fed during this process should not contain food coloring, preservatives, fancy flavorings or other processed additives. They should be pure ingredients so that the dog’s owner and veterinarian can accurately pinpoint which part of the diet triggers the allergy. 

Usually, the allergen is meat or some other protein source, although corn or other items can also cause hypersensitivity reactions. Once it is identified, the allergen should be removed from the dog’s diet, and its symptoms should quickly resolve. 

Fortunately, there is an increasing number of commercially-available kibbles that contain novel protein sources, such as venison, buffalo, rabbit, and duck. Owners of dogs with food allergies have a wide selection of dog foods to choose from and rarely will need to feed a homemade diet to enhance their dogs’ quality of life.

Symptoms of Food Allergies in Dogs 

Effects of Food Allergies – From the Dog’s Point of View

Food allergies, like most other allergies, cause animals to feel just plain lousy. The nature and extent of symptoms will vary between affected animals. A dog that is allergic to something in its diet almost always will show signs of having itchy skin. It will scratch, lick and bite at random areas of its body in what unfortunately will be an unsuccessful attempt to relieve its discomfort. 
Dogs with food allergies may also become nauseated and develop mild to severe gastrointestinal symptoms. If a dog is allergic to one of the primary ingredients in its food, or if it has multiple food allergies, its symptoms probably will be more serious than those symptoms of dogs that are allergic to only one minor component of their diet.

Symptoms of Food Allergies – What the Owner Sees

Food allergies are one of the most frustrating of all medical conditions for dog owners to deal with, particularly because it can take a very long time to isolate the offending food ingredient(s). Owners of dogs with food allergies typically start to see signs of a problem after their dogs have been eating a particular diet for several months.


Unlike the signs of food intolerance, the signs of food allergies usually do not come on suddenly. They develop fairly slowly and become progressively worse over time. Sometimes, food hypersensitivity symptoms don’t show up for a few years. Owners of dogs with food allergies may notice one or more of the following symptoms or signs in their pets:
  • Scratching, licking and/or biting at random areas of skin and coat
  • Hair loss
  • Skin sores/wounds; raw and oozing; self-inflicted in response to itchiness/pruritus
  • Skin redness
  • Raised skin bumps; pustules; hives
  • Skin Rashes
  • Redness and moist rashes inside the ear flaps
  • Nausea
  • Vomiting
  • Diarrhea
Skin reactions from food allergies tend to show up most frequently on a dog’s face, between its toes, on its groin and flank areas, behind the front legs (in the armpits or “axial” areas) and on or inside of the ears. In severe cases, dogs may develop hives, which are raised red bumps and pustules. 
When a food allergy affects a dog’s digestive tract, it may experience unexplained vomiting and diarrhea and may have more frequent bowel movements than normal. Whatever their exact symptoms, dogs that are allergic to something in their diet will be uncomfortable at best. Over time, they may become severely distressed, distraught or depressed as a result of their condition.


Treatment and Prognosis for Food Allergies in Dogs 

Goals of Treating Canine Food Allergies

The goals of treating a dog with food allergies are to identify and remove the offending components from the dog’s daily diet and to treat any secondary bacterial skin infections that may have happened as a result of the licking, scratching and biting that usually accompany this frustrating medical condition. 
Fortunately, food allergies are not especially difficult to treat. However, it can take a great deal of time and patience on the part of the owner to figure out which items in his dog’s diet are causing it to suffer from an allergic reaction.
Treatment Options for Dogs with Food Allergies
Dogs with food allergies can benefit from a number of different topical and oral treatments to help relieve the itchiness and discomfort that usually accompany this condition. First, however, the food ingredient or ingredients that are causing the allergic reaction need to be identified and removed from the dog’s diet. Once that is done, antibiotics can be administered to treat any secondary bacterial skin infections that may be present. 
Topical and/or oral antihistamines can help to relieve the itchiness associated with food allergies and can reduce the accompanying self-trauma from scratching and biting. Corticosteroids may be appropriate in some circumstances to reduce inflammation, although they can mask other symptoms and make it more difficult to determine a dog’s actual response dietary changes. The dog’s owner should discuss the possible side effects of any treatment with his dog’s veterinarian.
Prognosis
The outlook for a dog with food allergies is good to excellent, as long as the dietary ingredients that the dog is allergic to are accurately identified and removed from its daily meals. Owners have to be diligent and patient during the elimination diet process, and must not give their dogs access to any treats or foods other than those few pure dietary ingredients that they are supposed to be eating. Any variations can taint the diagnostic and treatment results and force the owner to restart the whole lengthy process.
Food Allergies in Dogs Food Allergies in Dogs Reviewed by DogRedLine on January 21, 2019 Rating: 5

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