Food Allergy
There can be two different syndromes associated with food allergy: a syndrome that affects the skin and a syndrome that affects the gastrointestinal tract. For simplicity, both syndromes will be covered here.
For either syndrome, there is a substance within the food that is causing the problem. For skin reactions, it is generally a specific protein or carbohydrate in the diet that is causing a hypersensitivity. Beef, chicken, lamb, corn, rice, and wheat along with eggs and dairy products are very commonly associated with this syndrome and can be found virtually in any commercial diet. These diets may not be "bad diets", but are bad for the particular pet.For gastrointestinal reactions, it can be associated with the ingredients above, but can also be due to additives, toxins within the food, or from spoiled diets.
Patients can show only one or both syndromes. They will scratch and chew excessively all over their body and routine antihistamines or steroids are not very effective at controlling the pruritus. The signs are year round as long as the pet stays on the same diet. This syndrome can be very difficult to differentiate from atopy as the signs can look the same.Pets can also have gas, diarrhea, anorexia, or vomiting. These signs can abate rapidly when the patient is not eating or when the diet has been changed inadvertently.
Fortunately, treatment is relatively easy and involves a dietary change. Unfortunately, it may take many dietary trials, especially with the skin reactions, to find an appropriate diet. For gastrointestinal signs only, sometimes just changing dietary brands with a different protein or carbohydrate from the current diet is all that is needed. With the skin reactions, a very restrictive prescription diet is usually needed. It is very imperative that the pet not receive ANYTHING orally for at least 8-12 weeks during the dietary trial to determine if the pet has a food allergy. Even some heartworm preventions have beef flavoring added. No treats, rawhides, or people food are allowed. These things can be added eventually after the trial is successful, but must be avoided during the initial period. After the pet is doing well, one ingredient at a time can be added to assess the patient’s reaction. Most animal will react within 3 days if that particular ingredient is the allergen. Once all the ingredients are identified, some commercial diets may be available that do not contain those allergens. If not, the patient will need to be on the prescription diet for life.
