Though many different conditions can affect the skin of both dogs and cats, the three most common causes of skin disease in both species are flea allergy, atopy and food allergy.
Diagnosing Skin Allergies Related to Food in Dog and Cats
In order to treat the itchiness and discomfort that accompanies skin allergies in dog and cats, it is necessary to treat the underlying allergy. In the case of food allergies, the only accurate means of diagnosing the allergy is to perform a food trial in which food products to which the dog or cat may have developed an allergy are eliminated from the diet.
- A food elimination diet is successful if the dog or cat becomes less pruritic (itchy) during the course of the food trial. This is step one in the food elimination trial and provides some evidence that the dog or cat's skin issues were food related.
- Ideally, once the pruritis has resolved the pet is challenged by returning to the previous diet. If the pruritis and other skin allergy symptoms return, it is considered additional evidence that the food is responsible for the skin allergy.
- Finally, the dog or cat is again returned to the elimination diet. If the response to the diet is positive and the skin allergy symptoms resolve, the food elimination trial has been successful in documenting a food allergy.
These steps seem logical in theory. In practice, many pet owners choose not to re-challenge their dog or cat with a food to which the pet is potentially allergic. In many cases, the food trial never goes beyond step one and the elimination diet is simply continued for the dog or cat rather than risking that the pet will become uncomfortable again as a result of returning to the original allergy-causing diet.
Performing a Food Elimination Trial for a Dog or Cat with Suspected Food Allergies
Being able to properly perform the food elimination trial is imperative to determining whether a pet is suffering from a food allergy. Dietary trial is the only means of diagnosis for pets with skin allergies related to foods.
- A thorough dietary history for the pet should be recorded, if possible. It is important to avoid any food items, particularly protein and carbohydrate sources, which the dog or cat has eaten in the past. Knowing what ingredients have been consumed in the past will aid in choosing a proper diet for the food elimination trial.
- A proper food must be chosen for the elimination diet. Ideally, this food will consist of a protein source and, possibly, a carbohydrate source that the pet has never previously been fed. Potential protein sources include duck, salmon, fish, kangaroo, rabbit and venison. Beef and poultry should be avoided. Potential carbohydrate sources include potato, sweet potato, oats, peas and green beans. Corn should be avoided. These diets are known as novel protein diets.
- Elimination diets may consist of commercially available pet foods and there are many prescription diets available that are adequate. Alternatively, diets may be home-cooked. It should be noted that if home-cooked diets are continued long-term, the diet should be balanced with the help of a veterinary nutrition expert.
- An alternative to commercially available novel protein diets are hydrolyzed diets. These commercially prepared diets contain proteins which have been broken down into segments small enough to be undetectable as allergens by the canine or feline immune system. Your pet's veterinarian can help you determine whether these diets are a suitable substitute for a novel protein diet.
- Food elimination trials should continue for a period of 6-8 weeks before being discontinued. While some dogs and cats may show a positive response sooner, others may not show improvement until near the end of the trial period.
- When performing a food elimination trial, it is important that no other food products be offered to the dog or cat. Treats, toys and flavored medications must be eliminated. This includes rawhide chews, dental treats and other forms of treats and chews. Also included are flavored monthly heartworm preventive medications, which may be replaced with unflavored oral alternatives or topical products.
Evaluating the Response of an Allergic Dog or Cat to a Food Elimination Trial
A positive response to a food elimination trial is a reduction and eventual resolution of symptoms associated with skin allergies.
If a positive response is not noted within the time frame of the dietary trial, the diagnosis of food allergy should be re-evaluated. In some cases, another food trial with a different type of diet may be warranted. In others, it may be necessary to consider other causes of skin disease, including other forms of allergies as well as other types of skin disease.
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