Definition of the Disorder
The term “allergy” is a general reference to a hypersensitivity reaction by the immune system to some “allergen”, which can be something in food, a grass or weed in the environment, flea saliva or dust mites, a chemical cleaner or other household product, or a number of other things. A more specific definition of “allergy” is an altered reaction to something (the allergen) following a second or subsequent exposure to it. The “allergen” is any substance that is capable of inducing an allergy or specific hypersensitivity. Virtually anything in the environment can be an allergen. The inciting contact with the allergen can be by physical contact, inhalation, injection or ingestion.
How Allergies Affect Dogs
Once a dog has been exposed to an allergen, subsequent exposure to the same substance will cause hypersensitivity (“allergic”) reactions. These can be local or system-wide and can occur immediately or be slow in onset. In dogs, the clinical signs of allergies most often appear as skin problems, ear infections or gastrointestinal upset. Most allergic reactions in dogs cause some degree of skin irritation; the skin becomes inflamed, itchy, irritated and red. Owners often report rashes, licking, scratching, biting, restlessness, pustules or bumps on the skin, “hot spots” where the skin becomes raw and infected, sneezing, red watery eyes and generalized lethargy. Dogs seem to be most commonly affected in the groin or flank area, on the paws, between the toes, in the ears, in the axial area (“armpits”) and under the neck. Secondary bacterial and yeast infections often occur, especially in the ears, accompanied by a foul, somewhat yeasty smell. Dogs with food allergies often have gastrointestinal disturbances in addition to skin irritation, such as burping, vomiting, diarrhea, flatulence (excessive production of intestinal gas), weight loss, hives and enlarged lymph nodes.
Causes of Allergies in Dogs
Most canine allergies are hypersensitivity reactions to flea or tick bites, contact or airborne inhalants or some ingredient in food. Allergies to fleas, which are extremely common in dogs, are caused by an immune reaction to flea saliva which leads to irritation and itchiness at the site of the bite, increasing the risk of bacterial infection and localized hair loss. Common contact and inhalant allergens include seasonal pollen, trees, bushes, grasses, weeds and flowers. These allergies, in dogs and people, are often called “hay fever.” Food allergies can be a reaction to essentially anything in a dog’s diet, but common food allergens include beef, dairy products, wheat, eggs, chicken, lamb and soy.
Preventing Allergies in Dogs
The best way to avoid allergic reactions in our dogs is to prevent contact with (or inhalation or ingestion of) whatever is causing the hypersensitivity. For example, flea bite allergies are best prevented by removing the allergen – fleas – from the dog’s environment. There are a number of good topical products to keep fleas off of our pets, including medicated collars and topical liquid treatments and preventatives, among others. To prevent hay fever, owners should keep their dogs away from whatever seasonal allergen is causing the problem. Food allergies can be prevented once the causative component of the dog’s diet is identified, which can be done through an elimination diet supervised by a veterinarian. Many commercial kibbles containing novel protein sources are available for dogs that are allergic to more common protein sources.
Special Notes
Canine allergies can be difficult, but not impossible, to diagnose and manage. Veterinarians can use a combination of a thorough medical history, physical examination, blood and/or skin tests and assessment of the dog’s response to treatment to identify and manage allergic reactions.