Food Elimination Trial
By Katie Simon
Cutaneous adverse food reactions (CAFR) are the third most common cause of allergy related problems in dogs. The most common allergy skin problem is atopy, followed by flea allergy dermatitis. In order to adequately diagnose a dog with CAFR, a proper food trial must be completed and owner compliance must be maintained. Although the exact cause of CAFR is not completely understood, there are many contributing factors. Failure of oral tolerance is regulated by gut associated lymphoid tissue, abnormal development of this tissue can cause an intolerance. Also to be considered is immunological food reactions. Food specific IgE antibodies on mast cells bind to the food antigen causing mast cell degranulation and release of inflammatory mediators. There may also be toxic food reactions that are dose related and due to toxins or histamine release.
Clinical signs associated with CAFR include gastrointestinal upset (vomiting, diarrhea, flatulence), non-seasonal pruritus (itching), otitis externa, popular dermatitis, and signs of self-trauma. Pruritus is mainly seen on the face, ears, feet, ventrum and perianal dermatitis. Lack of response to steroid therapy can also indicate CAFR. There is no increased risk related to age, breed or gender. Animals that have food allergies may also have allergies to environmental pollutants, inhalants, or other contact allergies. The most common foods that cause allergies are beef, dairy, chicken (including eggs), lamb, fish, corn, wheat, and soy products.
Dietary elimination trials are the only way to accurately diagnosis a food allergy. While the trial itself is straight forward, the actual process can be difficult for owner’s to complete. This consists of feeding the patient a prescription diet with novel protein and novel carbohydrates for at least 8 weeks. A novel protein is one that the patient has never had before, for example, venison, kangaroo, rabbit, etc. Hydrolyzed proteins can also be used. These contain proteins and carbohydrates that are broken down into small enough molecular sizes that are less likely to trigger an allergic response. Science Diet, Royal Canin and Purina all offer hypoallergenic and hydrolyzed protein diets that can be used for a food trial. Home-cooked diets can also be used, however, these are labor intensively and need to be formulated with a nutritionist. In order to ensure the patient is only receiving the food being given, every animal in the house should be given the same food and all bowls should be thoroughly washed. Absolutely no human food can be given during the first 8 weeks. If eliminating treats is not an option, there are hypoallergenic treats that can be used, but only these will suffice.
Along with changing the diet, the use of heartworm, flea and tick preventative will also have to be changed. Many of the oral preventatives contain animal by-products that could affect the food trial. Proheart and Advantage multi are approved for food trials, therefore, use of them will help yield more accurate results. After 8 weeks, if there is a reduction of symptoms, we begin challenging the diet with individual protein sources one at a time. If the symptoms return then we have found our culprit. If the animal remains symptom free, we add another protein back. Owners should start with about one tablespoon when adding protein and carbohydrate sources back to the feeding trial. Adjustments will need to be made based on size of the animal.
If it is determined that the animal does not have a food allergy, the best option is to do an allergy test to determine what environmental factors might be causing the problems. A food trial must be done first due to the fact that food allergens are not diagnosed with the allergy test. Treatment is based on avoidance. Once it is determined which protein is the inciting cause, the patient will need to have that specific product permanently eliminated from the diet.
Your veterinarian will be able to provide more information about whether your pet may benefit from a food trial.
Gunter, Juli. “Canine Cutaneous Adverse Food Reaction.” Starkville, MS. Mississippi State University College of Veterinary Medicine. September 2016. Lecture.
Lenox, DVM, DACVN, Gulf Coast Veterinary Specialists & Lenox Veterinary Nutrition Consulting, Houston, Texas, Catherine. "Food Trials." Food Trials. Clinician's Brief, 4 Oct. 2013. Web. 10 Oct. 2016.
Raditic, Donna. "Food Allergy Trials in Dogs." Food Allergy Trials in Dogs - VeterinaryPartner.com - a VIN Company! VIN, 15 June 2016. Web. 10 Oct. 2016.
"Understanding and Managing Your Child's Food Allergies." Choice Reviews Online 44.09 (2007): n. pag. Rocky Mountain Veterinary Dermatology, Inc. Web. 10 Oct. 2016.