Getting to the root of nutritional allergies

It is important to set the expectation that both cAFR and atopy are life-long medical problems to be managed

It is very common for pet owners to believe their itchy pet has a ‘food allergy.’ While cutaneous adverse food reactions (cAFR) are certainly not rare, when it comes to pruritic pets, atopic dermatitis (AD) is actually more prevalent than cAFR.
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It is very common for pet owners to believe their itchy pet has a “food allergy.” While cutaneous adverse food reactions (cAFR) are certainly not rare, when it comes to pruritic pets, atopic dermatitis (AD) is actually more prevalent than cAFR.1 Sadly, however, a physical exam is insufficient to distinguish atopic disease from a food-associated dermatopathy.

Adding further complexity, an estimated 30 percent of dogs and cats with food allergy have other dermatologic comorbidities, including atopic dermatitis.1,2 Given clinical signs of AD are indistinguishable from those of a true food allergy, one way or the other, an elimination diet trial will be a part of the diagnostic process. That said, nutrition can be used to help manage the clinical signs in both cAFR and AD.

Unfortunately, even without knowing the underlying cause of a pet’s pruritis, many owners may have already tried changing the animal’s diet in an effort to alleviate the clinical signs—in some cases, more than once prior to seeking advice from their veterinarian. This, of course, can serve to make the diagnostic process even more difficult, as data shows over-the-counter (OTC), limited-ingredient diets have a high possibility of undeclared ingredients, which may have, unknowingly, exposed a pet to a protein to which they may have a food allergy.3,4,5 This fact has created concern within the veterinary community even when using a veterinary-prescribed diet for an elimination diet trial. The good news, however, is evidence also shows prescription veterinary diets intended for use in an elimination diet trial are highly unlikely to contain undeclared proteins.5,6,7

Pre-trial research

Before starting any elimination diet trial, it is essential to obtain an extensive and thorough diet history. This is necessary for setting pet owners up for success, as well as making the veterinary team confident in the trial’s results.

To help streamline the process and gather more information, it is best to send a diet history form to the client in advance of an appointment for an itchy pet or other dermatological complaint. This is recommended even in cases where a pet’s owner has previously filled one out, as an updated form can provide an up-to-date snapshot of the patient’s history. Consider suggesting the owner also take pictures of any treats, foods, medications, or supplements they are currently giving to their pet. These images can be attached to a medical record and used to help further explore what, exactly, may ‘touch the lips’ of an itchy pet on any given day.

Veterinary prescribed diets

Many clients are skeptical of a veterinarian’s recommendation of a specific prescription diet. This may be because they feel they are simply being asked to purchase a more costly diet and do not see the value in this additional spend.

Part of effective client communication is to understand what preconceived notions a pet owner may have, then use the opportunity to educate them about the different levels of quality controls involved in the manufacturing of diets intended for use during an elimination diet trial (as well as those of OTC commercial diets, which are not intended for the same use). Dietary conversations are particularly difficult, as these talks often also relate to the human’s own personal values around nutrition. Nonetheless, pet owners, generally, want their veterinary team to provide dietary recommendations.8

Setting expectations

These communication strategies will also be needed to evaluate and confirm the pet owner’s readiness (and likelihood of adherence to) the nutritional recommendations prior to commencing on a journey of stringent dietary elimination.

As with all dermatological cases, open and honest communication and setting expectations is imperative to maximize success. These shared understandings between a client and the veterinary team are a key factor in helping a pet owner to accept they are taking on the challenge of a diagnostic test, which will take at least eight weeks to complete.9

Indeed, an eight-week-long diagnostic test is not a small ask of our pet caretakers. Making a comparison to another lengthy diagnostic test which the pet owner may be familiar with can help to make it an easier recommendation to ‘swallow.’ For example, ask the owner if they have known anyone who has needed to wear a Holter monitor for extended cardiac testing. This comparison helps in setting the expectation of diagnostic tests whereby the results are not immediately apparent or available.

Another important client discussion involves reassurance the limited diet and stringent rules for the subsequent eight weeks are not necessarily a ‘life-sentence’ for them or their pet. At the end of the strict elimination diet trial, the veterinary team can help to find ways to make the daily feeding routine a bit more flexible again.

Added flexibility may be necessary from a veterinary side, too. For some pet owners, asking for a shorter time commitment to start (four weeks, for example) may seem more attainable to them and give you time to eliminate some of the immediate discomfort of their pet. If the client starts to see improvements within these four weeks, they will be much more willing to continue the trial.

Finally, it is important to clearly define for the pet owner what, exactly, the veterinary team considers a positive test compared to a negative one. If the client expects the skin disease to be completely resolved, but the veterinarian is aiming for a 50 percent improvement, these mismatched expectations can lead to a frustrated pet owner.

Putting things in motion

When running an elimination diet trial, there are three nutritional strategies which are generally considered: hydrolyzed diets, novel protein diets, and home-prepared diets.

At present, hydrolyzed diets are the gold standard for an elimination diet trial.7,10,11 While novel protein diets can be used during the elimination trial, the growing number of exotic and boutique diets in the OTC market combined with the risk of undeclared proteins in OTC diets makes these less-than-ideal options for the duration of the elimination trial.

Lastly, home-cooked diets, while not as common as they used to be, remain an option. This is particularly useful in cases where the pet owner prefers to cook for their pet or where there are complex medical needs unable to be adequately managed with available commercial diets formulated for use during an elimination diet trial. If a pet owner elects to feed a home-cooked diet, this should be done in-consultation with a Board-Certified Veterinary Nutritionist to ensure the diet is complete and balanced. (Listings for these professionals can be found at

Each of these strategies has pros and cons to be considered, and there are times when one option may be more ideal for a particular pet. Ultimately, the strategy chosen will need to work for the person(s) who are doing the heavy lifting of the trial—the pet owner(s).

Next steps

As clinical signs of atopic dermatitis are indistinguishable from those of a true food allergy, an elimination diet trial will, in one way or the other, be a part of the diagnostic process.
As clinical signs of atopic dermatitis are indistinguishable from those of a true food allergy, an elimination diet trial will, in one way or the other, be a part of the diagnostic process.

What happens at the end of the elimination diet trial? Does this pet need to stay on this same diet?

If the diagnostic test was positive and there was a 50 percent or greater level of improvement in the clinical signs, it is recommended the pet remain on their complete and balanced elimination diet. Next, ideally, you would begin challenging the pet with different proteins one at a time to see if you can determine the protein(s) this patient cannot tolerate. This is called a “provocation trial” and, at this time, is the only way to definitively diagnose an allergy to a specific protein.12,13,14 In general, more than 90 percent of dogs and cats will show evidence of a cutaneous skin flare within 14 and seven days, respectively, from the time of challenge to an offending protein.15

Once a provocation trial has been done for any protein of interest, novel or limited-ingredient diets are excellent options to use as a maintenance diet if the pet owner would like to have alternative food options. You may also consider transitioning the pet to a multi-function diet if there are medical comorbidities which need to be considered in addition to the cutaneous adverse food reaction.

Finally, if the elimination diet trial is negative and the pet is then diagnosed with atopy (which, as mentioned earlier, is a diagnosis of exclusion), nutrition still plays a role in the management of the atopic pet. Diets formulated to support atopic skin contain supplements which will support skin-barrier function and help decrease inflammation. For example, many of the atopy diets contain supplemental omega-3 and omega-6 essential fatty acids—often in amounts higher than you can easily provide as a supplement exogenously. An added benefit to using the diet for omega supplementation is the additional calories have already been accounted for in the recommended feeding guidelines. These intentional and quantified calories can help to maintain a healthy Body Condition Score (BCS) for the patient, as pet owners rarely consider fatty acid supplements contain calories.

There are several published studies showing efficacy of atopy diets, and, in some cases, a decreased need for medication when atopy diets are used as a part of the multi-modal management approach.16,17,18,19,20 Data also shows the more treatments a caregiver needs to administer to a pet, the lower the assessed quality of life (QoL) of the pet owner.21 This certainly affects the human-animal bond, and so any opportunity to minimize the number of therapeutic treatments the owner must administer will increase the QoL of both the pet and the person.

In short

To summarize, dietary interventions are a cornerstone of successful management of many dermatology cases. A rational and systematic approach to the diagnosis is more successful with a detailed diet history.

Constructive two-way communication and shared decision-making with the pet owner engenders commitment to a long and often difficult diagnostic process. There are several diet options for the elimination diet trial and, regardless of the eventual diagnosis, dietary interventions can help to support an abnormal skin barrier. Setting both short- and long-term goals and expectations with the pet owner will minimize frustration and improve quality of life for both the pet and the pet owner. It is also important to set the expectation that both cAFR and atopy are life-long medical problems to be managed; frequent and early follow-ups, however, will ultimately improve the medical outcome, as well as the financial burden.

Juanita Glencross-Winslow, DVM, is a scientific communications specialist with Royal Canin Canada. A life-long educator, she relishes teaching both pet-owners and veterinary professionals. Much like ‘the cat that came back,’ after several years working in a private small animal practice, she returned to her alma mater, the Atlantic Veterinary College, as a clinical faculty member. Dr. Glencross joined Industry in 2010 and Royal Canin in 2017.


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