The Diagnosis of Dog Allergies
There are many conditions that can make a dog itch or have hair loss, including endocrine, autoimmune, infectious, and parasitic skin diseases. It takes some detective work to identify the cause. A veterinarian may be able to diagnose the problem or may refer your dog to a veterinary dermatologist, a specialist in treating skin conditions in animals.
If allergies are suspected, the first thing a veterinarian will usually ask is if the pet is on a flea-control product. Flea allergies are the most common type of allergies and the easiest to control. Dog owners have many options for flea control on dogs and in their environment.
Once flea allergies are ruled out and if the itch is non-seasonal, food allergies are checked next. Food allergies are not related to a season, while many atopic allergies start out as a seasonal problem. Dogs that develop atopic allergies usually show symptoms between 1 and 5 years of age, but food allergies can crop up at any time. They are high on the list of suspects when a dog first exhibits itchy skin at an age less than 6 months or over 5 years.
To test for food allergies, the dog is put on an “elimination diet” for at least 10 weeks, which means it is fed food that consists of a protein and carbohydrate that the dog has not eaten before, such as duck, venison, and potatoes. Veterinarians offer these special foods, and some may be found in retail stores. Or the owner may choose to feed the dog a homemade diet of foods recommended by the veterinarian.
If the dog’s itching subsides by at least half, the allergen is considered to be one or more food ingredients. To confirm this, the owner can reintroduce the old food to see if the symptoms return. To find the specific ingredients that trigger the allergy, the owner should feed the special diet again and add one ingredient at a time from the old diet for at least a week until the itching increases, indicating that the last added ingredient is an allergen. Or the owner may choose to stay with the special food to avoid causing the dog discomfort each time an allergic ingredient is fed.
While the dog is being tested for food allergies, it should not be given treats, chewable medications, table scraps, or rawhide toys that may contain an allergen.
To check for atopic and contact allergies, veterinary dermatologists use an intradermal allergy test, or skin reaction test. The dog is mildly sedated, a postcard-sized area on the side of the dog is shaved, and small amounts of potential allergens are injected into the skin on the shaved area. If the dog is allergic to a particular substance, the skin will become inflamed at the area of the injection.