Anyone who has seen a dog continually scratching and chewing on itself probably has seen a dog with allergies. Whether caused by airborne inhalants, fleas or ingredients in food, allergies cause discomfort that can range from simple irritation to severe secondary bacterial infections. The definitive cause of allergies is difficult, but not impossible, to diagnose. A veterinarian’s initial evaluation will include taking a thorough history from the dog’s owner about the dog’s health and symptoms, including when they started, whether they are sporadic or always present and whether they are progressively getting worse or staying about the same. The vet will also conduct a physical examination, paying particular attention to carefully assessing the dog’s skin and ears.
The most common cause of allergic reactions in dogs is also the most common cause of allergic reactions in people: seasonal hypersensitivity to something in the air or environment, like pollen, a particular weed or some crop being harvested in the area. Seasonal allergies usually can be diagnosed based on when the symptoms show up and the extent of the dog’s access and exposure to the environmental allergen. Flea bite allergies are also extremely common in dogs and are usually fairly easily diagnosed based on physical evidence of flea bites and flea infestation.
If an allergic reaction lasts for quite a while or occurs randomly rather than seasonally, it probably is caused by something other than a seasonal allergen. Advanced tests are available to help identify specific allergens. A veterinary dermatologist can discuss these tests with the dog’s owner in greater detail. Allergy testing is expensive, somewhat invasive and can be a bit painful. A less invasive way to diagnose the cause of a dog’s allergies is to systematically remove suspected allergens from its environment or diet and then slowly reintroduce them one at a time, evaluating whether the problem subsides or recurs. Fabrics, carpet fibers, dust mites, cleansers and detergents, household items made of rubber or plastic and even excessive dust can induce allergic reactions, so they should be considered in these cases.
If food allergies are suspected (and they are quite common in domestic dogs), the dog’s veterinarian probably will recommend what is known as an “elimination diet.” This means putting the dog on a bland diet with very few ingredients – typically just rice and chicken for starters. The owner will observe her dog for any adverse signs of reacting to those simple ingredients and, if none are present, will then gradually add other foods to the dog’s diet, one at a time. The owner must keep a close watch on how her dog reacts to each new ingredient to determine which food items he is allergic to. Once those are identified, the dog’s diet can be restructured.
It is extremely helpful to determine the source of an allergic reaction before a treatment protocol is established. Simply treating the affected area may help relieve the dog’s symptoms temporarily. However, the underlying cause of the allergic reaction probably will remain in the dog’s diet or environment and undoubtedly will cause additional uncomfortable symptoms in the future, if it is not identified and removed or managed.