New Food Allergies in Dogs

Changes in the diet that you feed your dog may uncover hidden allergies or cause new allergies to develop. Canines who develop allergies to foods experience severe inflammation and itching on the skin as well as chronic conditions such as ear infections, gas, and wheezing. An allergy is the response of the immune system to a perceived threat, in this case, an ingredient in the diet of the dog. In order to reliably determine which allergen is affecting your pet, an elimination diet may be recommended. This can be time-consuming, but is the most efficient way to deduce which ingredient is causing the reaction.

A food allergy is an over-reaction of your dog's immune system to an unwelcome protein that is present in an ingredient of their diet.

New allergies to food in canines can develop at any age, but the majority of food allergies don’t appear until they are at least three years old. Skin reactions are often centered around the face and groin, as well as under the front legs, or between the toes.

• Bald patches
• Chronic ear infections
• Chronic gas
• Chronically inflamed feet
• Coughing 
• Diarrhea
• Face rubbing
• Head shaking
• Hives
• Obsessive licking
• Paw biting
• Poor puppy or adolescent growth 
• Skin infections
• Skin rashes
• Vomiting
• Wheezing

Types

There are many reasons to change your dog’s diet, including the development of allergies to the previous food. Aging, the development of disorders like diabetes, and vitamin deficiencies are all conditions that would warrant a good, hard look at the diet your pet is currently on. There are many different dietary options available on the market today that can be beneficial to dogs who are prone to allergy. Many dog food manufacturers have options for dogs with special dietary needs, including breed specific formulations, formulas designed for easier digestion, and recipes with limited ingredients to reduce or prevent allergic reactions.

Allergies are due to an abnormally vigorous defensive response to a protein that the immune system considers to be an invasive substance. It is estimated that around 60-70% of the canine immune system cells actually reside in the digestive system. The process of digestion breaks down our foods into the smallest possible parts, known as amino acids. These amino acids are then absorbed by specialized white blood cells called enterocytes. When proteins are not properly broken down during digestion, these enterocytes see them as intruders and attack. Over time the response of these cells becomes more aggressive, and symptoms intensify. When a new food is introduced, it can instigate the formation of new allergies in sensitive individuals

Although any food can become an allergen, some ingredients are more likely to generate a reaction than others. Common trigger foods for canines can include:

• Beef
• Chicken
• Corn
• Dairy products
• Eggs
• Fish
• Lamb 
• Soy
• Wheat

Your veterinarian will want a thorough history for your pet, including diet, and any previously diagnosed disorders. This history, combined with the symptoms that are exhibited will prompt your veterinarian to collect skin scrapings from any affected areas for cutaneous cytology. Cutaneous cytology is the microscopic evaluation of the skin cells to look for problems like mites, yeast infections, or other signs of disease. The lack of an observable cause on the skin cells may indicate that an allergy is to blame. In order to confirm a food allergy, a switch elimination diet is usually implemented. An elimination diet usually involves changing the dog's food to either a reduced ingredient commercial food or a diet of unseasoned human food.  Novel ingredients are the most useful for an elimination diet, meaning that the proteins and carbohydrates in the replacement food should be completely new to the dog. In the case of allergies that have developed shortly after a change in food, each of the ingredients from both the current diet and the diet immediately preceding it should be avoided, in case the allergy is a delayed reaction to the previous food. In many cases it may be the entire food family that your pet is reacting to, so switching from a chicken diet to a mammalian source such as rabbit may have better results than switching to another avian species like duck. If the symptoms are caused by an allergy, a properly implemented elimination diet will cause them to cease and often times a complete switch to a dog food that is allergy friendly is helpful. 

Allergies to foods are not curable, but symptoms usually cease if the allergen is removed from the animal’s diet. Once the symptoms have ceased, additional ingredients will be slowly added into the diet until the particular allergen is identified. During this time, it is essential to ensure your dog does not ingest anything other than the food used for the elimination diet. A single treat with the allergen can cause the allergy to resurface. It can take several weeks for the elimination diet to reveal the allergen and during this time your pet may still experience the itchy and swollen skin. 

Use of treatments such as corticosteroids and antihistamines may make it harder to determine which ingredient in your dog’s diet is causing the reactions by masking allergic symptoms, so many veterinarians prefer to complete the elimination diet before applying these types of medications. Secondary skin infections are commonly seen with food allergies, and antibiotics may be prescribed to combat this problem. Once the allergen has been identified, the initial course of action is avoidance of the ingredient. Other supplements, such as Omega-3 oils and probiotics, may be recommended as well after the elimination diet is completed to support the immune system. This will assist your canine’s body to handle any accidental exposure to allergens and to prevent the cultivation of new allergies.

Any future exposure to the allergen can cause a relapse, so care must be taken in the type of treats and flavorings you offer your pet. Unfortunately, if your canine has had an allergic response to one type of food they are more likely to develop an allergy to the ingredients in the replacement diet over time as well. The approach to combat this situation varies within the veterinary profession, with some doctors advocating a steady rotation of three of four novel protein foods is optimal, while others maintain that your pet should remain on a single source of food.