June 2021

In this VETgirl online veterinary continuing education blog, sponsored by Blue Buffalo. Please note the opinions in this blog are the expressed opinion of the author, and not directly endorsed by VETgirl.

Veterinary therapeutic elimination diets—so, what’s the bottom line for usage?

By Alice Jeromin, RPh, DVM, DACVD

We’re all busy in the veterinary community so I thought I would offer up some concise reasons of when and why I use a veterinary therapeutic elimination diet (VTED). Important points will be made with the least amount of verbiage!

Choosing a Veterinary Therapeutic Elimination Diet
Obviously, a VTED is my choice in determining if a dog or cat has a food allergy. 33% of dogs with food allergy have clinical signs before 1 year of age and by 3 years of age, 83% of dogs with food allergy show clinical signs. Dog breeds such as Retrievers, German Shepherds, and West Highland Terriers account for 40% of affected dogs with other breeds predominating including Rhodesian Ridgebacks, Boxers, Pugs, and Shar Pei’s. Cats may start a bit later at age 3.5-4.5 years of age and Siamese or Siamese crosses may be predisposed. Options for diagnosis include feeding an elimination diet, either a veterinary therapeutic novel protein diet or hydrolyzed diet. Both have shown equal efficacy in the diagnosis and management of food allergy. Selection of a novel protein diet is based on a good dietary history-what has the pet eaten before as far as diet and treats? Does the owner even know? This point is vital if choosing a veterinary therapeutic novel protein diet. If the pet has eaten, for example, an over-the-counter (OTC) limited ingredient venison diet, then venison is eliminated as a choice for the VTED as the pet has already been exposed to this protein. If the dietary history is unknown, then a veterinary therapeutic hydrolyzed protein diet is the better option. Table 1. shows veterinary exclusive hydrolyzed protein diets and the initial source of protein for each product. The proteins are cleaved to be made smaller and hence, less allergenic. Palatability and diarrhea are said to be potential issues, but clinically these are rarely experienced. Diets need to be fed for 8 weeks for both dogs and cats in order to make a diagnosis. If the pet improves, then challenging with the former diet can either signify food allergy or food-induced atopic dermatitis (to follow).

Golden retriever beach

Image by Katrin B. from Pixabay

Signs of Food Allergy and Associated Conditions
Clinical signs of food allergy in dogs are varied (previously they were described as involving “ears and rears” but I disagree) and may include otitis (25-50% and may be unilateral only), erythema, excoriation, recurrent pyoderma-yeast or bacteria, pruritus, and/or gastrointestinal signs. Cats (who don’t like to do anything by-the-book!), may present with alopecia, pruritus, otitis, seborrhea, miliary dermatitis, or eosinophilic granuloma complex (EGC) lesions. Dermatologic clinical signs of food allergy may look like anything! Unfortunately, there is not ‘one’ particular clinical sign signifying food allergy so keep food allergy in mind when seeing ANY clinical signs of a nonseasonal allergic dermatitis.

One out of 5 dogs and cats presenting with pruritic skin disease have food allergy as an underlying issue. Cats seem to present most often with vomiting (among other clinical signs) and dogs can have various GI clinical signs to include gastritis, small bowel diarrhea, and colitis. Up to 29% of cats with inflammatory bowel disease may respond to a VTED. Food-induced atopic dermatitis occurs when the atopic dog (not much research on this in cats yet) flares upon eating something that causes the body to think it is the same thing that aggravates him/her as their atopy allergen. Evidence in humans and now in dogs suggests that certain foods may trigger symptoms of atopy. Potential causes of this include food-inhalant interaction where some foods appear the same as inhalants to the body. Examples include cedar/tomatoes in dogs, house dust mite/shellfish in people and many others. A former study of nonseasonal affected house dust mite allergic dogs when kept on Prescription Diet Z/D diet for a year, 36/123 experienced very few flareups but when challenged with their regular diet, 50/123 flared. A good reason to have our atopic patients on an elimination diet as the less flareups, the better! If we can reduce atopy flareups with diet, then systemic medications can either be avoided or minimized. And the less drugs, the less potential adverse effects or drug interactions!

Food allergy may play a role in several systemic diseases such as epilepsy, lupoid onychodystrophy, vasculitis, erythema multiforme, and immune mediated diseases such as pemphigus foliaceus. Since most of these involve long term medications with potential adverse effects, it makes sense that if a diet can help in any of these diseases…why not add a VTED? A 1993 study by Dr. Ed Rosser claimed 10% of food allergic dogs presented with seizures. Most veterinary dermatologists include a veterinary therapeutic hypoallergenic diet as part of their treatment plan in lupoid onychodystrophy.

Avoiding Contaminants
There are several studies to support that serum testing (IgG, IgE), saliva or hair testing, or skin testing are not reliable in the diagnosis of food allergy. VTED fed for 8 weeks along with a re-challenge of the pet’s former diet is the current best method for diagnosis of food allergy. Owners trying to avoid certain ingredients most commonly targeted in food allergy (dogs-beef, chicken, wheat, dairy/cats-chicken, beef, fish) unfortunately cannot rely on OTC food labels to correctly identify what is contained in the food. One study indicated 83% of pet food labels did not correspond correctly with what was actually in the food. This, among other reasons such as better quality control, nutritional research, and improved fatty acid content, is why veterinary therapeutic elimination diets (and veterinary therapeutic diets (VTD) in general) are recommended. Food manufacturers such as Blue Buffalo (HF, NP), Royal Canin (Ultamino), and Rayne (kangaroo, rabbit) perform ELISA testing to be sure their therapeutic elimination diet products do not contain protein contaminants. If choosing an elimination diet for long-term use in a young dog, be cognizant of those approved for growth (See Table 2). Royal Canin Vegetarian (RCV) was helpful in 3 food allergic dogs when animal protein could not be tolerated. Raw diets have been found to be contaminated with other proteins- raw diets for dogs were found 78% of the time to be contaminated with lamb protein and raw diets for cats 56% of the time were contaminated with turkey. Allowing owners to feed their own formulated cooked diet is not acceptable as 95% of owner generated cooked diet recipes were found to be deficient in nutrients. If a cooked elimination diet is desired, www.balanceit.com or several universities such as The Ohio State University and Tufts University have nutrition departments willing to help formulate recipes.

Bottom Line
So, the good news is that VTEDs are certainly the way to go when diagnosing food allergy…and they may also help in atopy, lupoid onychodystrophy, and immune mediated diseases. There is not one food that “fits” every pet and sometimes several diets (especially in cats!) need to be tried before you find one that is successful. Consulting with the owner and explaining that this is not a quick process is essential. I find that owners that are themselves food allergic or have food allergic children tend to understand the process and how “one little piece of cheese” really DOES HURT!

Learn more about BLUE Veterinary Therapeutic Elimination Diets HERE:


VETgirl Blue Buffalo Veterinary Therapeutic Hydrolyzed Diets and Protein Sources chart

VETgirl Blue Buffalo Veterinary Therapeutic Elimination Diets Approved for Growth in Dogs or Cats chart

  • BLUE Natural Veterinary Diet, HF Hydrolyzed for Food Intolerance and NP Novel Protein are registered trademarks of Blue Buffalo
  • Prescription Diet and z/d are registered trademarks of Hill’s Pet Nutrition
  • ProPlan Veterinary Diets, HA Hydrolyzed are registered trademarks of Société Des Products Nestlé S.A
  • Rayne Clinical Nutrition and Rabbit-MAINT are registered trademarks of Rayne Clinical Nutrition
  • Royal Canin, Hydrolyzed Protein Adult HP, Ultamino, Selected Protein PD, Selected Protein PR, Selected Protein PV and Royal Canin Vegetarian are registered trademarks of Mars

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