Just cutting the chicken won’t cut it! Tips and tricks on how to perform successful diet trials

 

Performing an elimination diet trial is a crucial step in the diagnostic workup of pets with non-seasonal pruritus. One of the most common comments we hear from owners of allergic pets is their desire to ‘get to the root cause’ of their pet’s itching, but this cannot be done without a proper diet trial.

Introduction: 

• Getting to the "root cause" 
• Essential to allergic pet's work-up 
• Daily basis comment from clients: want to get to root cause of pet's itching rather then continuing symptomatic management 

Ultimately in order to get to the root cause of a pet's itching, we have to do a diet trial. There is really no way to get to the root cause and identify whether or not we're dealing with food allergies, environmental allergies or a combination of both, unless we actually do a proper diet trial

What is a  food allergy? 

Immunologic Trigger: Adverse food reaction that triggers the immune system to a food item

•  Not dose dependent meaning pet's that are allergic to something in their food really don't need a lot to trigger significant symptoms
• Common clinical sign in cats and dogs: Pruritus = Itching

Pathogenesis 

•  Type 1= IgE or Immediate hypersensitivity 
• Classic anaphylactic-type: Rapid onset of symptoms within minutes to a few hours of ingestion 
• Clinical signs (sometimes combined, sometimes individually) :
• Dyspnea (difficulty or labored breathing), 
• Urticaria (hives)
• Angioedema, 
• Flushing (Itchy skin, Digestive Issues, Eye Allergies, Skin Irritation) 
• Pruritus and erythema (itching and redness)
• Vomiting/diarrhea 
• Pallor and shock (Non-Regenerative anemia and blood pressure drop)
• In patients that have IgE- mediated hypersensitivity food allergies 
• Those food items that pass through the gut they are presented to the immune system and instead of activating more of a T regulatory cell pathway they activate the T helper 2 cell branch of the immune system which ultimately leads to the development of B cells and plasma cells and allergen-specific IgE antibodies, which end up on the surface of mast cells that are then ready to activate when they cross-linked by that food allergy in the future leading to rapid histamine release and the clinical symptoms that are those that we associate with anaphylactic reactions in animals due to the activity on the portal vein we see more gastrointestinal-type symptoms like vomiting, diarrhea and eventually if untreated potentially shock. 

•  Type IV= Cell- mediated or delayed hypersensitivity (Most seen in pets)

○ Second pathway for food allergies : Slower/delayed onset of symptoms after a few days or weeks of ingesting allergen

○ More consistent with clinical picture in cats and dogs-  Ishida et al.2004:

                        Type IV hypersensitivity in 82% of dogs with FA

• In Patients that have cell mediated/delayed hypersensitivity 
  The immune system still has to be activated so instead of developing tolerant type T regulatory cells the T helper 2 branch of the immune system is activated here as well but rather than specifically formulating IgE antibodies to those foods, it releases more of the inflammatory Cytokines  (interleukins 4,6,13, 31) all of those typically associated with atopic dermatitis- type clinical symptoms. 

• In non-food related patients When food passes through the gut the immune system will present these food items to the immune system and that should trigger a T regulatory cell pathway to secrete sort of, anti-inflammatory or tolerant-type cytokines, like interleukin-10 and TGF-beta
  
  
  so that when that food is eaten in future, the body recognizes it as something that it tolerates. 

Food Allergy Clinical signs 

○ Clinical signs Type I

•  Dyspnea (difficulty or labored breathing) 
• Urticaria (hives), Angioedema ( swelling, particularly in the face and respiratory system
• Symptoms include red, raised bumps in the fatty layer under the skin, causing discomfort) , Flushing (Itchy skin, Digestive Issues, Eye Allergies, Skin Irritation), Pruritus' and erythema - itching and redness, 

In a study over 20 years old it was thought that over 80% of dogs have Type IV more delayed hypersensitivity reaction. Clinical signs: 

Type IV Secondary infections 

Secondary infections are very common in pets with allergies. These can include bacterial infections or Malassezia dermatitis, as well as recurrent ear infections. Up to 25% of pets with food allergies may present with recurrent ear infections, and in some cases, this may be the only clinical sign observed. These infections are usually bilateral, although some patients may present with unilateral otitis.

Hot spots are another common finding, particularly in Golden Retrievers. Less commonly, dogs may show classic anaphylactic or IgE-mediated reactions such as hives and facial swelling.

More rarely, a variety of immune-mediated diseases have been linked to food allergies as a trigger: 

•  Symmetric lupoid onychodystrophy (SLO)
• Perianal fistulas
• Pemphigus
• Erythema multiforme. 

For dogs with these conditions, diet trials or investigating food allergies is considered a gold standard approach.

Symmetric Lupoid Onychodystrophy (SLO): A condition characterized by the rapid and painful loss of multiple toenails, often beginning with a single nail. The nails become brittle, misshapen, and may fall off, exposing the nail bed to infection. SLO is considered an autoimmune disease, where the immune system targets the nail growth area.

Early signs are often first noticed during grooming sessions observing: 

• Brittle or splitting nails, abnormal nail shapes, excessive nail breakage, or sensitivity when handling the paws. 
• Dogs may pull away, show discomfort, or have mild inflammation around the nail beds before more obvious nail loss occurs. 

These subtle changes can be an important early indicator, allowing for earlier veterinary evaluation and intervention.

Cutaneous signs in Dogs 

Signs of the classic kind of atopic food allergic patients 

- Redness and itching - Face = muzzle, lips, eyes, ears; armpits; groin, perianal area

- Flexural, elbows

Note: It's very similar to what we see in environmental allergies the chart below is to demonstrate how there is a lot of overlap between good allergy distribution patterns and environmental allergies.  

Just based on looking at  a dog or breed you can't tell whether or not that patient's going to have a food allergy or environmental allergies.

Cutaneous signs in Cats

Pruritus (itching) is one of the most common clinical signs associated with food allergies. In cats, over 90% of those with food allergies will exhibit itching and scratching. The face is the most commonly affected area, followed by the neck, caudoventral abdomen, and ears, although some cats may develop a more generalized distribution. Compared to dogs, the pattern in cats is much more variable and less predictable.

This has an important connection to grooming practices. Cats experiencing underlying pruritus are often mistakenly perceived as having poor coat quality, matting, or hygiene issues. As a result, they may be subjected to more frequent or unnecessary grooming interventions such as excessive brushing, shaving, or bathing.

However, these grooming practices can inadvertently worsen the condition. Over-grooming whether self-induced by the cat or externally through repeated grooming sessions can further irritate already inflamed skin, disrupt the skin barrier, and increase the risk of secondary infections. Cats with facial or ear pruritus may also become more sensitive to handling, making grooming stressful and  leading to defensive behavior.

The grooming process itself can also be highly stressful for cats, especially those already experiencing discomfort from itching. Cats are sensitive to handling, noise, restraint, and unfamiliar environments. When their skin is inflamed or painful, even gentle grooming can feel uncomfortable or threatening. This can lead to heightened anxiety, fear-based behaviors, and increased resistance during grooming sessions.

Stress is not just a behavioral concern it can also worsen dermatologic conditions. Increased stress may intensify itching and grooming behaviors, creating a cycle where the cat becomes more pruritic, more reactive to grooming, and more difficult to handle safely. In some cases, this can lead to overgrooming, self-trauma, or delayed healing.

Early signs are often subtle and may first be noticed during grooming. These include:

• Mild hair thinning
• Mild Dandruff
• Broken hairs
• Small scabs
• Redness
• Increased sensitivity in commonly affected areas like the face, neck, and abdomen. Rather than indicating a need for more grooming, these signs should raise suspicion of an underlying allergic condition.

Recognizing that pruritus not coat neglect is the root issue is critical. In these cases, reducing unnecessary grooming and recommending veterinary evaluation for possible food allergies or other dermatologic conditions is the most appropriate course of action.

4 different "reaction patterns" some cats will have just one, others will have a combination of several 

1. Eosinophilic granuloma complex

○ Is a clinical presentation of allergies = Not a disease

•  Rodent ulcers unilateral or bilateral 
• Symmetrical ulcers of the upper lip 
• Eosinophilic plaques - raised often ulcerated, itchy
• Secondarly effect leads to infection: commonly noted  but not limited to the caudal ventral abdomen
• True granulomas often seen in the mouth, the fat lip often along the caudal thighs, they can develop in other locations. 

2. Miliary Dermatitis 

 

• Little punctate, crusted papules can be anywhere on the body as well as self-induced

3. Self-Induced Alopecia/ hypotrichosis 

• Overgrooming leading to hair thinning or hair loss, depending on how long they have been licking. 

4. Head and Neck Pruritus 

• Which can be very intense leading to dramatic self -mutilation and injuries 

** Note similar to dogs all these four reaction patterns can be seen in food allergic cats  or in Feline Atopic Skin Syndrome (new term for environmental allergies, then flea allergy dermatitis). You can't just look at a cat and decide whether or not we're dealing with food allergies or environmental or flea allergies. 

Age of Onset

Review paper done in 2019: Age onset has a huge variation anywhere from puppy and kitten hood, all the way up to senior years and anywhere in between. 

Mean Age of Onset:

Dogs: Typically 2–3 years of age, however, up to 40% of dogs with food allergies will develop symptoms before one year of age.

Cats: Typically 3–5 years of age, with approximately 25% showing signs before one year of age.

This differs from environmental allergies, where about 75% of dogs and cats will begin showing clinical signs between one and three years of age.

Clinical Relevance to Grooming Observations:

Because food allergies can present at a much younger age than many pet professional or owners expect, early clinical signs are often subtle and easily dismissed especially in pets under 2–3 years old. There is a common assumption that young animals are “too young” to have allergies, which can delay recognition or be misdiagnosed as environmental (Season, Grooming products ect).

In grooming settings, these early signs may include: 

• Mild itching
• Slight coat thinning
• Dandruff
• Hot spots
• Small areas of hair breakage
• Intermittent ear debris
• Subtle skin irritation.

 In cats, this may appear as overgrooming in localized areas like the face, neck, or abdomen. In dogs, it may include early ear issues or paw licking.

Because these signs are mild and the pet is young, they are often misattributed to normal shedding, grooming sensitivity, behavior, or minor coat issues rather than an emerging allergic condition. This can lead to increased or unnecessary grooming interventions, which may further irritate the skin or increase stress, particularly in cats.

Recognizing that food allergies frequently begin before the “expected” age range is key. Early detection of these subtle grooming-related changes allows for timely veterinary referral, helping prevent progression to more severe pruritus, secondary infections, and chronic skin disease.

Food vs Environmental Allergies 

• Age of onset can potentially increase your suspicion of food allergies but ultimately cannot be used conclusively for diagnosis. So if you have a cat or a dog that develops symptoms really young or potentially older outside that classic one to three years of age, food allergies is more suspicious but not conclusive for diagnosis. 

• Identifying the "root cause" cannot be done without investigating food allergies first. So we do know the root cause which is Allergies the question is whether those allergies are food-related or environmental or a combination of both. The first  step needed to determine the long-term treatment plan needed for these pets, because Food allergies and environmental allergies are treated very differently.

Food Allergies:

Food allergies are a lifelong condition, meaning affected pets will require ongoing management throughout their lives. However, with an appropriate diet  such as a properly selected elimination diet, or a balanced hypoallergenic formula clinical signs can often be well controlled or even completely resolved. With consistent feeding of the correct diet and avoidance of trigger ingredients, many pets experience significant improvement in pruritus, skin health, and overall comfort without the need for continuous medication.

Environmental Allergies 

These pets will rely on some form of medication lifelong  to manage their symptoms. 

Trying to figure out that root cause whether or not we are dealing with food, environmental, or both is really important step at the beginning. Trying to figure out that root cause whether or not we are dealing with food, environmental, or both is really important step at the beginning.  Typically diagnosed based on clinical history, age of onset, pattern of symptoms, and by ruling out other causes. Intradermal skin testing or serum allergy testing may be used to help identify specific environmental triggers.

Combination cases (both food and environmental) are common, especially when symptoms are only partially controlled with one approach.

Diagnostic Tests for food Allergies

Most commonly being performed, done by reputable labs (IDEXX, ANTEC), unfortunately they are as accurate as flipping a coin and they are not inexpensive. 

Why they are considered unreliable is because the vast majority of dogs and cats it's not a true IgE mediated, food allergy, so there probably are some IgE antibodies here and there and those that have really acute hive-like reactions this might be more helpful, though even that hasn't really been shown: 

False positives are common in our healthy and environmentally allergic dogs, and false negatives are common in pets with food allergies. Even when you submit blood from the same pet multiple times it is very common to get different results each time. 

Don't bother doing serum allergy testing for food. 

For environmental allergies definitely do

 keep in mind still not a diagnostic test. Still food must be ruled out first then use the environmental allergy test to figure out what environmental allergens that pet's allergic to, as opposed to making that primary diagnosis of environmental allergies. 

Picture: The listed studies highlight: Two separate groups of dermatologists that submitted to two separate tests; either saliva from dogs with allergies, saliva from healthy dogs, then tap water, as far as hair they submitted hair from healthy dogs, hair from allergic dogs, and then hair from stuffed animals and there were no significant differences in results they got back from these allergy tests. Not only are they unreliable it is questionable what tests they are even running to try to come up with your stuffed toy being allergic to chicken or beef. 

A very common one, these are available directly to consumers. All owners can google food allergy tests online and they will be hit with a huge selection of hair and or saliva tests that will apparently tell whether your pet is allergic to certain food items. 

They produce beautiful panels of red items, orange items, green items things to avoid that are ok but unfortunately they are also very unreliable. 

Certainly something done for environmental allergies but unfortunately for food allergies they are also not very reliable.  In  lab setting with beagles they did have some reasonably accurate results, but when that was extrapolated to clinical practice with dogs from all different breeds from different backgrounds and different diets, unfortunately false positives and false negatives, are very common. So we can't rely on these either.   

Picture: The idea is your grinding up different ingredients that you want to test for and make a bit of a paste out of them and then put them in contact directly with a pet's skin and then wrap them up and send them home and have them come back in 48 hrs and look and see where they have developed reactions on their skin. 

Final result demonstrated pretty reasonably good for negative predictability. So if a dog did have a negative result = No reaction to that ingredient, highly likely that they were not allergic to that item.  If they had a positive result or they developed a little red bump or hive that did NOT mean they were actually allergic to that food, but rather the result could be potentially be helpful into guiding what ingredients to use for diet trial elimination. If whatever you patch test resulted negative, it is likely going to be a safe ingredient to trial for keeping in the diet. However it doesn't get you out of actually doing the diet elimination trial. 

They are not very user friendly, creating the little troughs where you grind up all the different ingredients, making the pastes, sending clients on their way for 48 hrs and then coming back isn't very easy to do, especially sort of in a referral setting where owners are often driving several hours for their appointment then coming back two days later isn't ideal. On top of that it doesn't get them out of doing a diet trial.  

Picture:In 2004 a study found that it was about 94% accurate when compared to food trials and challenges. So if it said that they were positive for reaction and then you challenge them with that food there was about 94% accuracy and they would get the right one.

It had 100% positive predictive value= if you were positive dog likely has or does have a food  allergy  and 93% negative predictive value. 

How this test works: A blood sample's drawn and then spun down to get polymorphic blood nuclear cells, which are then incubated with the food item of choice for six days and given a radioactive tag and then you watch and see what percentage of lymphocytes are activated. This test looks for the lymphocyte mediated response. 

Issue: it is a difficult test to perform, because that spinning down has to happen within hours of collecting blood, which is not really very easy to do in a clinical setting where we are collecting blood from patients and then sending it out overnight to the lab to get tested the following day.  

Accuracy rate of 84% meaning - It as accurate in 84 % of cases to identify the correct food allergen, not just they where positive. Note it still has to be taken with a grain of salt and consider in coworking with elimination diet trials. 

Elimination Diet Trial

Over-the-counter diet trials can be challenging and often frustrating, as they must be done very strictly with 100% compliance to be effective. Any variation in the diet intentional or accidental can interfere with results and make the trial unreliable.One major concern with over-the-counter diets is ingredient variability. Some products may contain trace ingredients not clearly listed on the label or may be subject to cross-contamination during manufacturing. This makes them a less reliable choice for true elimination diet trials.Strict monitoring is essential during a diet trial. Pet owners must carefully track every ingredient the pet consumes, including the primary diet, treats, table scraps, flavored medications, and supplements. Even small exposures to an allergen such as a single treat or flavored chew can invalidate the entire trial.

It’s also important to confirm whether the owner is feeding anything “on the side.” Many pets continue to receive treats, dental chews, or human food without realizing the impact this has on the trial. These extras are one of the most common reasons diet trials fail.

The idea of home-cooked diets, is picking a single total novel protein mixed with a novel carbohydrate. The problem is  they are nutritionally  inadequate for long term feeding and growth. Studies have shown that compliance is very poor for these as well, due to the work required to cook these diets. 

Prescription diets  either novel protein or hydrolyzed protein makes it easier to process the elimination trial as  they are structured to be limited in ingredients as well as nutritionally adequate. 

For a diet trial to be successful, the pet must consume only the prescribed diet with no additional foods or flavorings for the full duration of the trial. Consistency and careful ingredient control are key to accurately determining whether a food allergy is present.

Picture: This common review paper is from the early 2000s and some even from the 90s and these certainly are the most common ingredients we use to feed pets. 

For a food allergy to develop, the pet must first be sensitized. This means the immune system has been previously exposed to a specific protein and has mounted a response. This can occur through:

• Type I hypersensitivity, involving antigen-specific IgE antibodies 

• Cell-mediated responses, where T-helper cells proliferate and release inflammatory mediators upon re-exposure 

Because of this, a pet cannot be allergic to a protein it has never encountered before. 

This is the basis for using novel protein diets in elimination trials.

For example: If a pet has never been exposed to chicken such as when a breeder has intentionally avoided it then chicken is unlikely to be the cause of an allergic response. In this case, a chicken-based diet could actually be an appropriate option for a diet trial.

This highlights why diet history is critical. A complete and accurate record of everything the pet has consumed kibble, treats, table food, supplements, and flavored products is essential to selecting an appropriate diet.

There are two main approaches:

• Novel protein diets: selecting ingredients the pet has never been exposed to 

• Limited ingredient diets: using a small number of controlled ingredients, sometimes overlapping with previous exposures, to monitor reactions 

Protein selection is key, as proteins are the primary triggers of food allergies and are typically the last components systematically challenged during a structured trial.

Ingredient exposure goes beyond just the diet. Many topical products and supplements can also contribute to skin reactions or complicate the clinical picture. Ingredients such as oatmeal, brewer’s yeast, raw food components, fish oils, glycerin, egg, wheat, plant-based ingredients, vegetables, fruits, spices,  tapioca,  chicken vs chicken meal vs chicken-by- product,  can influence differently how the immunity responds depending on the dog it can sooth, trigger, or masking underlying issues.

For example:

• Certain fruits, vegetables, or plant-based ingredients (including herbal extracts and spices) may act as hidden exposure sources or irritants in sensitive pets

•  Oatmeal-based shampoos may soothe some pets but can be problematic in others with sensitivities 

• Oils and glycerin-based products can alter the skin barrier, sometimes improving or sometimes worsening conditions depending on the pet 

• Brewer’s yeast and certain proteins (like egg or fish) may contribute to flare-ups in sensitized animals 

If a pet’s skin condition fluctuates despite grooming changes or worsens after certain products this may indicate an underlying allergy rather than a grooming issue. Understanding both dietary intake and topical exposure is essential for identifying triggers and supporting a successful allergy management plan.

Picking the diet Novel Protein

Picture: Most common novel proteins would be the ones noted above. 

The problem with novel protein diet is that it's becoming increasingly difficult to source, a lot of pets have had a whole slew of ingredients because owners have been trying to find something that works on top of treats, in addition to table foods. 

Egg? Pork? oatmeal? vegetables? spices? plant-based? Because a lot of diets do have these ingredients in them along with other variations it becomes difficult to pinpoint what caused what and which ingredient causes IgE reactivity vs Delayed hypersensitivity, vs Seasonal - environmental allergy. 

Performatrin diets

have multiple proteins: Beef, pork and multiple plant-based ingredients, in addition to spices, certainly common diets that pets are fed.

Acana 

have multiple proteins: Duck and fish and multiple plant-based ingredients, in addition to flavoured supplements and probiotic and spice another common diet fed.

 

Ingredients

Turkey, Rice, Corn Protein Meal, Chicken By-Product Meal, Animal Fat Preserved with Mixed-Tocopherols, Soy Protein Isolate, Poultry By-Product Meal, Fish Meal, Soybean Meal, Wheat Flour, Dried Egg Product, Natural Flavor, Dried Chicory Root, Gelatin, Fish Oil, L-Lysine Monohydrochloride, Salt, Phosphoric Acid, Potassium Chloride, Choline Chloride, Vitamins [Vitamin E Supplement, Niacin (Vitamin B-3), Vitamin A Supplement, Calcium Pantothenate (Vitamin B-5), Thiamine Mononitrate (Vitamin B-1), Riboflavin Supplement (Vitamin B-2), Vitamin B-12 Supplement, Pyridoxine Hydrochloride (Vitamin B-6), Folic Acid (Vitamin B-9), Vitamin D-3 Supplement, Biotin (Vitamin B-7), Menadione Sodium Bisulfite Complex (Vitamin K)], Magnesium Sulfate, Minerals [Zinc Sulfate, Ferrous Sulfate, Manganese Sulfate, Copper Sulfate, Calcium Iodate, Sodium Selenite], Dried Colostrum, Taurine, L-Ascorbyl-2-Polyphosphate (Vitamin C). D862922

e.g. The Purina Essential Care kind of  kitten or adult ones actually do have multiple proteins Turkey, fish, chicken-by-product meal, plant-based products, and dairy 

You really need the diet history to see whether or not that would potentially be an option for novel protein for a pet. 

Picture above:  All the proteins on the left are major allergens in chicken for dogs, and then looking at the similarities of these in salmon and white fish. Yellow being partially cross reactive and red being fully cross reactive. 

They are all partially or fully cross reactive . While in an in vitro setting there is cross reactivity between IgEs we don't know if you actually fed a  dog with a chicken allergy, a duck diet or turkey diet, whether or not they would react. 

Certainly some people will use these as novel proteins. Because of that potential cross-reactivity  we don't want to have any wish washiness to our diet trials o we can truly see if they are or are not food allergic. 

Concept of Cross Reactivity- Major food allergens in pets have been well identified, with chicken, beef, fish, and egg being among the most common triggers. These proteins are not only frequent in pet diets, but they are also molecularly similar to proteins found in other food sources, which can contribute to cross-reactivity.

It is important to note that when we discuss allergens in this context, we are primarily dissecting the protein components of foods, as proteins are the main triggers of immune responses. However, cross-reactivity is not limited to animal proteins. Pets can also develop sensitivities to:

Plant-based ingredients: vegetables, fruits, legumes, grains, and plant-derived additives

Dairy components: lactose, milk proteins, colostrum

Supplemental or functional ingredients: probiotics, brewer’s yeast, algae (e.g., kelp)

Furthermore, environmental allergens such as pollen, dust mites, mold, and fleas can contribute to or exacerbate reactions in sensitive pets, overlapping with food-related sensitivities 

Understanding that cross-reactivity exists across animal proteins, plant-derived ingredients, and environmental factors is essential when selecting diets, planning elimination trials, or interpreting recurring skin and ear issues. 

By focusing on both the type of protein and potential cross-reactive ingredients, we can more effectively identify triggers and design a diet or management plan that truly addresses the pet’s underlying sensitivities.

In a recent study there was a lot of  homology between proteins in chicken and fish. 

It's better to avoid duck , turkey based for dogs in pets that have had chicken.  Avoid venison, Bison or lamb, beef liver for dog's that have had beef based diets. 

Other option is to avoid that cross-reactivity of trying to find something novel when a dog has literally had every protein available.  Is to go with a hydrolyzed protein. Behind these is that the most common food allergens are between 15 and 40 kilodaltons. In hydrolyzed diets the molecular weight is much smaller less than  5 kilodaltons, so if it is small enough you can't actually cross-link on IgE and then leading histamine release.  

If there is no IgE crosslinking on the surface of mast cells then histamine is not released and we don't get the IgE-mediated type allergic reaction. 

Which The non- IgE mediated allergy (delayed) is the most common in pets. So even though less than 5 Kilodalton's is what we need to prevent IgE gross-linking  peptides of less than 0.5 are able to induce T lymphocyte mediated reactions. 

A 2020 In vitro study: They looked at Hill's ZD and Royal Canin Anallergenic to see if they would induce lymphocyte responses and luckily they found that it was only really enough in 2% of the blood that was tested that would be a threshold that we would consider positive for a food allergy.  Likely hydrolyzed diets are going to be safe, but there are a couple of studies that have shown that if you feed a dog a protein that they are allergic to even in a hydrolyzed form they may still react. 

A much older study had about 20% of dogs that had a sap soy allergy react to Purina HA vegetarian, then more recent study, a colony of chicken allergic dogs where fed Hills ZD and 40% of them reacted or flared up, in  that same group they were fed Royal Canin Anallergenic, which is much more extensively hydrolyzed than ZD so the proteins are in fact really small down to the amino acid level, those dogs did not react to Royal Canin Anallergenic- something to be said that our hydrolyzed diets are not hydrolyzed enough for dogs that have allergies to that specific protein.  For that reason hydrolyzed chicken based or hydrolyzed fish for dog's that have had fish before, tend to stick more with hydrolyzed soy cause that's a less common ingredient that pets will have had in their previous diets.

Veterinary Technician pointed out:  She was trying to find a food for a cat and looking through different ingredients and found most of the kitten ones she was looking at - general wellness ones- did have soy meaning most kittens will be already exposed to soy from an early age. This highlights the importance of looking through your diet history not only for novel proteins but for hydrolyzed proteins as well. 

Duration of the Trial

Requires a lot of commitment but worth it long term. About 50% of dogs and cats are going to improve around that three to four week mark which means that the other 50% do need more time.  So it should hit 80% to 85% at the five to six week mark and then 90 to 95 at the eight week mark. ** It is recommended to do the full 8 weeks in order to make sure nothing is missed. 

Important step during diet trail: Patients need to be treated while they're on their diet trial. 

Case Study: 

Figure shows: A westie who's owner had fed 3 or four different diet trials by the time he was taken to dermatology evidence based clinician, prior it was not getting better.They where adamant that food allergies was not possible, clinician asked them if pet always  looked like that when they did the diet trials and the owner responded she had never seen her dog  not look like this since her allergies started. 

Findings

- Bilateral Otitis 

- Malassezia Dermatitis

- Superficial pyoderma

It would be impossible to ask a diet to treat all these stacked up infections.  Infections need to be cleared to see whether or not the diet's will work or not. Infections need to be treated based on cytology, treat the itch and inflammation which is being experienced and then try to prevent secondary complicated factors like fleas or mites by using ectoparasite prevention. 

NNew guidelines include: Treat all surface and superficial pyoderma with topical therapy alone: Chlorhexidine based shampoos, mousses, wipes, sprays, potentially antimicrobial ointments on individual lesions - Isoderm, Mupirocin etc. 

To treat an active infection something needs to be used consistently and daily. However if the level is at preventative care then one to three times a week situation. 

If there is Malassezia dermatitis you need to use something that has 3% or higher chlorhexidine vs bacteria 2% is in fine.  Or use a combo shampoo or 2% chlorhex wirh 2% miconazole then recheck every 2 to 3 weeks to make sure these infections are resolved. 

The systemic antimicrobial therapy is acceptable and the SKAG guidelines as far as empirical antibiotics: If infections are not resolved with topical therapy alone or if topical therapy is not feasible on top of  pet size complications-  a Newfie needing a bath every single day for three weeks is a big ask

Dogs: 

More inflamed dogs with interdigital nodules (highly inflammatory) - 6 weeks tapering course of prednisone, prednisolone, dexamethasone  for the duration of the diet trial. 

Cytopoint during diet trails: Not the first go to due to variations of duration. Some dogs get six weeks, some get 4 weeks so you might need to repeat trial, after the first trail wears off due to variation of duration. For easier process you may need 12 weeks of trial and Cyto combo to be able to see if it works. 

Cats: 

6 week tapering course of steroids. Atopica will take four to 6 weeks before it works which is the only on-label medication for cats which have environmental allergies. 

Recurrent ear infections as part of their manifestation allergy medications won't have anti-inflammatory so it will not prevent ear infections from happening.  So add in a topical steroid. Go to is Cortavance or Cortotic due to it's more potent activity. Mild cases Burrows and Pro-Otic HC which are hydrocortisone 1% for small dogs 1/4 ml twice a week, bigger dogs or medium dogs half a mil twice a week. 

One chew of the Bravecto which has hydrolyzed pork used at the beginning of the diet trial lasts 12 weeks is probably fine the rest is going to be topical. 

Coming to the end is evaluating whether or not it was successful. Westie in the picture: 12 weeks after the diet trial, off steroids 4 - 6 weeks. No medications and is doing great, confirming she was food allergic. Goal is 50% or greater clinical signs. In an extremely sensitive dog such as the one above is pretty obvious for dogs minimally affected it can be harder therefore the itch scale is helpful to guide owners towards to be more observant on degree of pet itch at the beginning and see if it drops.

Evaluation of success

Getting  50% or greater response, next step is to go to that dietary challenge. Either not food allergic and basically diagnosed environmental allergies, poor compliance from owner, or you picked the wrong diet. 

Food allergies still suspected due to pet developing symptoms at 3 months of age, they have a lot of gastrointestinal signs, try another. Infections are still present so cytology again super important to make sure infections are gone, those could be causing a false negative result. 

Once a pet has completed an elimination diet trial, the next critical step is the reintroduction phase, often called the diet challenge. This helps confirm whether the pet truly has a food allergy.

1. Reintroduce the previous diet and all treats the pet was receiving prior to the trial. This includes flavored medications, supplements, table scraps, and any other food items.
2. Observe for flare-ups:
   • If a flare occurs within approximately 14 days, this supports a diagnosis of food allergy, and the next step is to conduct individual ingredient challenges to identify the specific allergens.
   • If no flare occurs within 14 days, it suggests the pet is not food allergic. Improvement during the diet trial may have been due to:
     • Removal of a treat or ingredient that was a trigger
     • Resolution of concurrent diet-related issues
     • Seasonal environmental factors (e.g., not allergy season)
3. Incorporate grooming observations:
   • Subtle signs noticed during grooming—such as mild redness, broken hairs, flaky skin, or early overgrooming—can provide additional context during both the elimination and challenge phases.
   • Groomers’ records of changes in skin or coat condition can help correlate flare-ups with specific diets or exposures.
4. Complement with diagnostics if needed:
   • Veterinary diagnostics such as skin cytology, ear cytology, or intradermal/serum allergy testing can help rule out secondary infections or environmental allergies.
   • Monitoring for recurrent ear infections, hot spots, or changes in nail health (e.g., early signs of SLO) may indicate underlying inflammatory or immune-mediated issues that are independent of diet.

The combination of diet trial results, careful reintroduction, grooming observations, and diagnostics allows for a precise identification of food allergens. Pets that do not flare after the challenge likely improved due to removing incidental triggers or other factors, rather than having a true food allergy. This systematic approach ensures unnecessary restrictions or interventions are avoided and that management strategies are accurately tailored to the pet’s needs.

How quick to flare: Around half will start to flare by reintroducing their food. The fifth day then about 80-90 % at the seventh day. By day 14 you'll get over 90% of patients. While it takes 8 weeks for dogs and cats to get better on a food, a worsening is seen within the first week to two weeks.

Usual full two weeks is done particularly for cats. It's hard sometimes to see their flareups because it can take time for them to show symptoms if their heavy closet lickers so the 14 days is the cutoff as to whether or not they will flare. 

For long-term management of food allergies, individual dietary challenges are a key step. Once specific ingredients have been identified as safe or triggering, these results can be used to guide owners toward a diet that is both safe and practical for everyday feeding.

For example:

• If a pet does not react to a challenge with rice, and also shows no reaction to a challenge with fish, then a diet containing fish and rice is likely to be well tolerated for long-term feeding.
• It is important to consider all other ingredients in the diet formulation. Even if the primary protein and carbohydrate sources are safe, additives such as oils, plant proteins, probiotics, or flavorings could trigger reactions in some pets.

Long-term management is therefore a combination of:

1. Confirmed safe ingredients from elimination and individual challenges
2. Careful review of full ingredient lists for commercial diets
3. Owner education about avoiding accidental exposure to treats, table scraps, or flavored supplements

By tailoring the diet to the pet’s unique sensitivities, owners can maintain skin and coat health, reduce pruritus, and prevent secondary infections, while also feeding a diet that is palatable and practical for everyday use.

Issues with compliance as well as issues with wrong diet selection can attribute to almost 80% of misdiagnosis of ruling out food allergies. Inability to give treats with medication. Biggie is diet cost. 

 

 This is the way we will diagnose the food allergy and a way to potentially avoid a lifetime of symptomatic medications, treating flareup after flare-up antibiotics and ear medications, symptomatic medications like Apoquel and Cytopoint if a dog really doesn't need them because they have a food allergy.

The initial investment of two months into a prescription diet at the beginning can actually save you a ton of money, if it gets diagnosed. 

Performing diet trial over a holiday, you can wait until after the holiday and try then.

Dog's getting into things that they shouldn't do to best of abilities, accidents are going to happen, when they do take note of what was ingested and monitor for symptoms.  

Modern veterinary medicine acknowledge owner self-confidence - not feeling like they are capable of doing this, mostly seen in owner's lack of confidence in their pet's (a lot of owners don't think their dog or cat is going to eat the recommended food for eight weeks) 

**Note all hydrolyzed diets are 10% palatability guaranteed, if pet won't eat it just return and try the next one, then keep trying until one is found. 

When planning long-term management of food allergies, it’s important to consider owner preference, but only as long as it supports improvement in the pet’s condition rather than perpetuating unresolved issues.

Some owners may have strong beliefs for example: that certain breeds like Rottweilers or German Shepherds cannot do well on vegetarian or novel protein diets. While respecting these preferences is important, it should not prevent trying appropriate dietary options if the pet’s health requires it.

The goal is to balance:

• Owner compliance and willingness to feed a diet consistently
• Nutritional adequacy and safety for the pet
• Clinical outcomes, including reduced pruritus, healthier skin and coat, and prevention of secondary infections

In some cases, this may involve:

• Selecting alternative diets that align with the owner’s comfort level but are still free of identified allergens
• Informing owners about successful outcomes in pets on novel or limited-protein diets
• Reassessing ingredients and ensuring no hidden triggers in treats, supplements, or flavored medications

Ultimately, the priority is the pet’s well-being, and the diet must resolve the allergy issue rather than simply fit preconceived notions. Owners who understand this are more likely to comply and see meaningful, long-term improvements in their pets.

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This webcast is held in collaboration with the Canadian Academy of Veterinary Dermatology.