How to conduct a hypoallergenic diet trial
Pets with suspected food allergy are best tested with diet trials but blood tests can also be helpful. Even the allergy labs caution against over interpretation of food allergy test results as they can be unreliable. The list of the allergens tested (pollens, wool, flea saliva, etc.) are more reliable results. My rule of thumb is treat high reacting food designations as probably believable but a non reacting ingredient as always suspect until proven ok by a diet trial.
What is a diet trial? It is a strictly controlled limited antigen (protein in the ingredients) diet fed to the pet (yes, cats have food allergies too). Fun fact- 80% of these trials are done wrong the first time! Hence this article. Why does this happen?
1. It takes too dang long to explain! (Hence this article again) Ask questions if you don’t understand something.
2. Pet owner just randomly switched the diet.
3. People think “diet” only means canned or dry pet food and give all kinds or additional items they consider “not dog food” such as rawhide, pig ears, dog biscuits, cheetos, and popcorn.
4. Failure of the person doing the trial to get the rest of the household to follow the plan. Hint: Bold threats help!
5. Leaving food items not on the trial within reach such as the other dog or cat’s food lying around. These must be inaccessible to the trial pet. Another hint you usually can feed all the dogs the trial diet.
6. Leaving the pet outdoors where he may be contacting food or other allergens. This can be neighbors giving the pet treats or even backyard fruits. Pick up other pet’s poo, it can contain allergens too!
7. Too many concurrent allergens in addition to the food allergens. This is where the allergy test helps a lot.
8. Concurrent diseases such as secondary bacterial or yeast infections must be treated or the pet will continue to be itchy, flaky, and stinky even if the allergy is handled by the new diet. And don’t forget the flea control!
Okay, okay but how is this trial done properly?
1. Doctor suspects a food allergy because:
A.) The pet has itchy skin especially the feet and often ear infections when it is under a year of age.
B.) If a new diet or treat was started a few days or weeks before the signs appeared.
2. Find out what the pet has been eating and identify all of the protein containing ingredients in them (see previous article on how to do this).
3. Make a list of all of these called the “suspect list” and/or get allergy testing with the food panel to sort out the bad ones.
4. Choose a diet that has no suspect items and also have only one to three (usually 2) new proteins in it.
-Pets under 1 year of age may still be sensitizing to new proteins. Choose a hydrolyzed diet from the vet.
-Hydrolyzed diets can’t stimulate allergies and are used for pets under 1 year of age and also for older pets that the owner hasn’t a clue as to what they have eaten in the past or they seemingly have eaten everything known to man prior to heir first birthday.
More succinctly, a novel (never eaten it before) limited ingredient diet or hydrolyzed diet.
*You can get properly formulated “homemade” diet specially made for unusual ingredient requirements or for picky appetites.
5. Find hypoallergenic treats because if you don’t, someone will give your pet contraband!
A. Commercial hydrolyzed treats. (mostly from the vet)
B. Non-protein items
-Marshmallows (pure carbohydrates)
- Potato or corn starch “bones” if you can find them.
Do not feed pure fats as treats because they are notorious for inciting pancreatitis.
C. Additional novel protein. This means you are certain your dog has never eaten this as a puppy.
-Commercial delicacies- duck, quail, goose
-Wild game- pheasants, barracuda, elk
-sweet potato fries
In the U.S.A., beef , dairy, chicken, wheat, corn, and soybeans are the most common commercial ingredients so always avoid these in trial diets unless you know for a fact there is no exposure to these as a puppy/kitten. (Do you know what the breeder fed the litter? Me neither!)
How long of a trial?
- Usually 2 – 4 months (buy enough for concurrent pollen allergy pass.)
- If a pet has only a food allergy (no pollens, house dust mites, etc.) they will be cleared up within 3 weeks.
-If the pet clears up re-feed the suspect diet. If itchy, flaky, stinky skin returns, you are reasonably certain that a food allergy is present. This can occur with just a couple of meals or in a week.
-If itching, return to the trial diet before significant skin or ear problems develop.
-If not itching, consider that a non food allergen disappeared during the food trial. Get an allergy test if not already done.
Stay on the trial diet forever or find a new diet.
A. Find the individual allergens by sequential addition to the trial diet. For example- add chicken meat daily for a week. No itching= chicken on the okay list. Put corn meal on the trail diet daily= itching in 2 days= put corn on the forbidden list. And so on until you know what is okay and was isn’t. Then find an appropriate diet.
B. Take a chance and buy a diet with none of the suspect ingredients in it and wait for the itch. If no itch, you win! If they itch, give away the food and take another shot.
C. Compromise and buy a commercial novel diet- duck & potato, etc.
-Dog gets along great for 6 months and starts itching again- pet owner thinks the diet “quit working”. Not! Either contraband was ingested or it is that time of year for his pollen allergy, got fleas, mites, etc. See the vet, don’t go off of a diet that has worked for months!
-Dog food company changed the ingredients and didn’t personally call you about it. Keep old pet food ingredient labels and be suspicious if the bad skin or ear infection started after you brought a new bag home.
-Got the wrong bag- OOPS!
- Had a party and didn’t separate Popeye the Pug from guests. Barbeques are too tempting.
-Chewable medicines – Vets hate when the beef/pork chewable vitamin, heartworm, flea/tick, and joint meds are allergens for your pet. Get non flavored products.
-The obvious, to misquote Freud “Sometimes an ear infection is just an ear infection. ” Don’t chew out the family and find out it was a foxtail seed in the pet’s ear causing the infection. (again see the vet first.)
- Multiple allergens persistent in the environment! Another subject for the next article.
-William I. Wiatt D.V.M.