What are the symptoms of food allergies?
Affected dogs have cutaneous (skin) and/or digestive symptoms:
- itching, especially on the ears, feet, face, armpits, groins, under the tail and on the rump;
- infections in both ears that come back often;
- bacterial skin infections ;
- vomiting ;
- diarrhea and/or gas.
Secondary lesions such as crusts, scabs, pimples often appear due to bacterial infections and trauma that the dog inflicts on himself.
Are there breeds more often affected than others?
Indeed, some breeds have food allergies more often than others. This is the case for :
Food allergies appear at what age?
Food allergies can appear at any age. However, dogs younger than 6 months or older than 6 years are more often affected.
What is a food allergy?
A food allergy is an abnormal reaction to an ingredient normally found in food. This ingredient that makes the dog react is called an allergen. It is almost always an animal or vegetable protein.
What are the ingredients or foods that cause food allergies?
The ingredients recognized as causing allergies most often are as follows, in decreasing order :
- Dairy products
- Chicken eggs
The elimination diet trial: what is this test?
The first diagnostic step to take requires an elimination diet trial. It consists of providing the dog with food that contains a minimum of potentially allergenic ingredients for approximately 2 to 3 months. The goal is to check whether the symptoms disappear or not. Skin symptoms usually go away within the first two weeks. Digestive signs can take more than 6 weeks to disappear.
This test is the only reliable method for diagnosing a food allergy. The dog absolutely must not eat anything else. This includes non-hypoallergenic treats, chewable bones and strips, table scraps, dietary supplements, toothpaste and flavored medications, etc.
What kinds of food should be used for the test?
The test should be done with hypoallergenic food. One of these 3 kinds :
- Hydrolyzed proteins (e.g. Hill's® Prescription Diet® z/d™, Royal Canin® Hypoallergenic HP™, Purina® HA Hydrolyzed™)
- Novel protein (e.g. Hill's® Prescription Diet® d/d™, Royal Canin® Hypoallergenic™)
- Home cooked
Hydrolyzed proteins are proteins that are cut into very small pieces. The immune system does not recognize them because they are too small. Therefore, it does not react to them. This type of food is ideal for testing.
Novel protein foods generally contain a single protein and a single source of carbohydrates (sugar). The limited number of ingredients reduces the risk of the dog reacting to it. This type of food is not ideal for testing because the immune system can start to react to the intact proteins.
Hypoallergenic homemade diet recipes exist. It is essential to follow them to the letter for the results to be reliable. It must also be ensured that no food allergen contaminates them during their preparation, which can be difficult to do.
How is a food allergy confirmed or excluded? With provocation
Provocation consists of reintroducing the old diet after the test is over and to observe if the symptoms reappear or not. These can manifest up to two weeks later. This step confirms or excludes the diagnosis of food allergy.
We can try to identify which food allergens the dog reacts to after causing symptoms to return. Here's how:
- Repeat the avoidance diet until the itching and lesions have completely disappeared.
- Add one ingredientat a time to the diet and watch for the symptoms to come back in the next 2 weeks.
- Do the same with the other ingredients.
With hypoallergenic food
The dog should eat a complete and balanced hypoallergenic food for the rest of his life. This therefore excludes hypoallergenic foods prepared at home because they are nutritionally deficient. Dogs that eat a novel protein food can become allergic to it. You must therefore be attentive to the return of symptoms with this kind of food.
Drugs that control allergies fall into 2 categories. On the one hand, there are anti-inflammatory drugs (e.g. prednisone) which reduce inflammation. On the other hand, there are antipruritics (e.g. oclacitinib) which relieve itching by preventing the stimulation of nerve fibers present in the skin.
With over the counter products
A variety of excellent skin products are available on our shelves. They are used in addition to hypoallergenic foods and medications to control symptoms and to treat secondary infections.
These products include:
Food allergies are part of a long list of different causes of itching. It is important to follow the requisite steps to identify the right cause or causes.
Is your dog scratching a lot? Get an appointment in one of our establishments to have him examined by a veterinarian.
Text put online on April 28th 2020.