Food trials for allergies and sensitivities
The food trial is a diagnostic test, just like a blood test or skin scraping. The difference between a food trial and other tests is that it is carried out over a longer period of time, and in your own home. You, the owner, are responsible for making sure that the test is carried out properly so that the results are as useful as possible.
In a nutshell, we will put your pet on a new diet, which must be strictly adhered to for a period of 10-12 weeks. During the trial he is to get NO other food. (More about this later.)
We are doing this food trial because food allergy or food intolerance is a possible diagnosis. The goal of the food trial is to "clean up" the system, stop the input of any possible food allergens, and allow antibodies made to previous allergens to wane. Ultimately we hope that this also clears up the dermatitis and itching or gastroenteritis.
The key to this process is to stop feeding any ingredients that the pet has had before, and put them on something truly novel. And when I say any ingredients, I mean any. If a pet has had chicken, beef, wheat, corn, lamb, rice, venison, fish, potatoes, turkey or whatever, at any time in its life, we have to eliminate those ingredients. With some pets this can be quite difficult, especially dogs who have been fed a laundry list of foods previously.
The food selected for a food trial may contain novel ingredients or may contain hydrolyzed proteins. In the "novel ingredients" category there are specific dry (kibble) diets that have unusual protein sources, usually a single type, that are not commonly available in store-brand pet foods. Examples of this might be kangaroo and oats, or venison and green peas, or a vegetarian food. These diets are only useful if the animal has never had those ingredients before.
Another novel ingredient food that we have had good success with is a cooked fresh diet made by Rayne Clinical Nutrition. They started as a local company (Burnaby) and have developed these diets with veterinary nutritionists, so we know that they are balanced. They consisted of a single meat source (rabbit, kangaroo, pork) and a single carbohydrate source. They are very palatable (what animal doesn't like cooked meat?) and come frozen in individual trays.
In the hydrolyzed protein category are prescription dry foods. These diets are made from proteins that have been broken down (hydrolyzed) into small segments that the body cannot recognize as being allergens. The base protein is usually chicken or soy, but because the protein is hydrolyzed they should (in theory) be hypoallergenic even to pets with chicken or soy allergies.
The choice of diet depends on your pet's previous diet history, including maintenance diet, snacks, chews, and people food. In some animals, especially dogs who are fed table scraps, it is easiest to go right to a hypoallergenic food or a two-ingredient fresh food rather than trying to determine which obscure ingredient might be safe to feed.
Cats might do better on a home-cooked trial with controlled ingredients, or on one of the Rayne Clinical Nutrition diets. They are more finicky eaters than dogs, in general, and are much easier to prepare homemade food for simply because they don't eat as much.
If a commercial hypoallergenic diet is fed, keep in mind that most cats do better on the canned formulations than dry. We don't know why this is, but it is a phenomenon noted by many veterinary dermatologists.
A vegetarian diet is never, ever a good idea for cats; they are obligate carnivores and will develop serious nutritional deficiencies if they do not get meat.
The important thing in an elimination food trial is to do it once, do it right so that there is no question as to whether it was helpful, and then to return to an appropriate commercial diet. This commercial diet may or may not be what your pet was eating before we started the food trial.
In order to maximize the information that the food trial gives us, and to make all of the effort worthwhile, you will need to follow a few simple rules.
1. Introduce the diet gradually over a 7 day period to avoid an abrupt food change that might cause diarrhea. Mix in the new diet ¼ new to ¾ old for two days, then ½ and ½ for a few days, then mostly new, then completely on to the new diet.
2. Nothing is to pass your pet's lips except the recommended food.
3. All treats, flavored medications or vitamin supplements must we withheld.
4. The feeding dish should be glass, ceramic or stainless steel (not plastic).
5. Do not feed homemade diets long term without discussing mineral and vitamin supplementation.
6. Make a note of the amount of itching and skin lesions that you see at the beginning. Assess how often you are seeing scratching, how red the ears are, how many spots there are on the abdomen. Every two weeks reassess the skin and the amount of itching.
7. Stay on the diet at least 8 weeks. We usually recommend a 10-12 week trial before deciding that it is not working. If it is helping, you may see improvement earlier. Keep in mind that it will take at least 6 weeks for the body to be cleared of previous allergens and for antibody levels to start to decrease, so don't give up if you have been feeding for a month and don't see improvement. Tough it out.
8. Outdoor pets should be confined during the course of the trial to prevent them from getting other foods. This is particularly important for those dogs and cats that tend to roam the neighborhood begging from neighbors or raiding garbage cans.
9. Glucocorticoids (Vanectyl-P or prednisone) may be needed for humane reasons early in the dietary trial to control intense itching and skin lesions. The food trial must be continued 2-3 weeks beyond the effects of the drugs.
10. Secondary infections with yeast or bacteria should be treated while the food trial is being started. This includes ear infections.