Allergy examinations in dogs
The most common disease that causes skin and ear problems in dogs is allergy. Itching is the most common symtom of an allergy. The reason for the allergic symtoms may be food allergy or atopy, which means that the dog is allergic to something in the environment. Worldwide flea allergy is the most common allergy, but it is rarely a problem in Finnish dogs.
Ear inflammations is one of the most common symtoms in allergic dogs.
The allergy may cause eye symtoms such as itching and irritation around the eyes, conjunctivitis, discharge from the eyes and redness.
How is food allergy diagnosed?
Pet owners are often very aware of that food allergy may cause skin symtoms. Food allergy is, however, much more rare in dogs than atopy is. In the beginning of the allergy examination the veterinarian wants to sort out whether the symtoms are caused by the food that the pet is eating or something in the environment, such as dust mites.
All symtoms caused by foods is not allergy. Lactose intolerance in humans is a good example. All food allergic dogs don’t have symtoms from the gastrointestinal tract.
Food allergy can not be diagnosed with blood samples at the moment. The most common method to test for food allergies is an elimination diet trial, during which the dog eats food that it is probably not allergic. At the beginning of the trial itching and inflammation is treated with drugs and topical treatments. After the diet the dog’s symtoms are compared to the ones it had before the diet. If the dog is better off when it eats the elimination diet food, the provocation phase is started. In addition to diagnosing or outruling food allergy, we also want to find out what the dog can eat and what it should not be fed.
The most common allergy symtom is itching. When the dog’s paws are itching it licks them, and the licking can discolour the the paw hairs.
In addition to itching, another common symtoms of allergy is redness of the skin. Very many allergic dogs have inflammations in their paws. Allergy caused dermatitis may have yeast or bacteria.
How do we know if a dog has atopy?
Atopy is a clinical diagnosis. This means that the symtoms and the progression of disease are compared to the typical ones of atopy. There is no particular test, for example a gene test, to make a diagnosis. It is very important to go through the anamnesis when doing an allergy examination. This is why we book an hour for the first visit and recommend that the owner takes the patient history with them or sends it to us by e-mail before the visit.
Next other possible causes for the symtoms are ruled out, such as parasite diseases. Often an elimination diet trial is needed. To recognize bacteria or yeast infections samples are often taken from the skin or the ears.
There is often overgrowth of yeasts in samples from dogs with allergic dermatitis. Yeast is a normal inhabitant of the skin, but as a result of allergy the yeast can thrive a little too well and make the skin inflammation worse.
The skin barrier of an allergic dog is weaker and the skin therefore more prone to infections than in a normal dog. The dog in the picture has folliculitis caused by bacteria.
When do we make an allergy test?
There are no tests that can tell us that a dog has allergy. In allergy tests also healthy dogs may have positive results, so it is not possible to use tests to make an allergy diagnosis. Tests are usually used in order to choose allergens for an immunotherapy, not for diagnostics. The allergy test result can however support the allergy diagnosis.
Allergy tests can be made as skin tests or by taking a blood sample. Skin tests are not always available. With the blood sample, the dog’s allergen specific IgE antibodies can be revealed. The allergens of the test are chosen based on where the dog lives: here in northern Europe the most common allergens such as pollens, dust mites and storage mites are important.
Because of the itching the dog is scratching its skin and this may result in a hot spot (acute moist dermatitis). Hot spots are typically seen in dogs with a thick fur in the summer and often after swimming.
Allergy tests are used to choose the allergens for immunotherapy. Atopy can not be diagnosed with an allergy test.