Elimination diet for dogs and cats - Comprehensive guide

An elimination diet is a temporary, strictly controlled feeding trial used to determine whether a pet's (dog or cat) symptoms are caused by a food allergy[1]. In practice, during an elimination diet, the pet is fed only one new food for several weeks, with all previous foods and treats excluded. If the pet's skin or gastrointestinal symptoms improve during the trial and return when the old food is reintroduced, it can be concluded that the symptoms were caused by the food[2][3]. The only reliable way to confirm a food allergy is precisely the elimination diet, followed by a controlled challenge with the original food[4].

The elimination diet is recommended when, for example, food allergies are suspected behind recurring skin or gastrointestinal problems. However, before starting the diet, it is important to treat other possible ailments, such as ear or skin infections, because a dietary change does not cure infections caused by bacteria or yeast[5][6]. External parasites (such as fleas) and environmental allergens must also be controlled so they do not interfere with the results of the food trial. A veterinarian can assess the pet's condition and guide the implementation of the diet, as the elimination diet requires commitment and precision from the owner.

Note: The elimination diet is not suitable for all situations. It is avoided in growing puppies, pregnant, or very weak individuals, as a monotonous diet can cause nutritional deficiencies in them[7]. If necessary, a veterinarian can tailor an elimination diet for a growing pet, but usually allergy tests are scheduled outside of growth or pregnancy periods.

Pet allergies can be roughly divided into environmentally caused atopic tendencies (e.g., pollens, dust mites, molds) and food allergies. Atopy (i.e., atopic dermatitis) is clearly more common in dogs – it is estimated that about 10–15% of dogs suffer from atopy caused by environmental allergens[8]. Food allergies are rarer: literature reviews have found that only about 1–2% of dogs and less than 1% of cats seen by veterinarians have true food allergies[9]. On the other hand, among pets that do have chronic skin symptoms (itching, rash, etc.), a fairly large proportion ultimately turn out to be reactive to food: various studies show that even 9–40% of dogs and 12–21% of cats with long-term itching were food allergic[9]. This means that food plays a role in the disease of many pets with skin problems, even though purely food-induced allergies are quite rare in the overall population.

What causes allergies? Allergy is an overreaction of the immune system to a substance that should normally be harmless. Hereditary predisposition plays a major role – certain breeds, such as Labrador Retrievers, German Shepherds, French Bulldogs, and Westie Terriers, have a high incidence of both atopic skin disease and food hypersensitivities[10]. Environmental factors, weakening of the skin's protective barrier, and repeated exposure to allergens (such as certain pollens or proteins commonly found in the diet) can trigger symptoms. Cats can also develop atopy and food allergies, although there is less research on the mechanisms of feline atopy[11]. It is essential to understand that allergies are chronic conditions – they do not heal on their own, but symptoms can be managed by avoiding allergens and, if necessary, with medication. In the treatment of food allergies, foods that provoke symptoms are avoided, and the first step is to determine the offending substance through an elimination diet.

Symptoms: The most typical symptom of food allergy in a pet is severe itching and related skin symptoms. In dogs, food allergy often causes a similar itchy skin problem as atopy: the dog may scratch and lick itself, especially the paws, ears, muzzle, belly, and rear end, and redness, pimples, hair loss, or inflammations develop on the skin[12]. Recurrent outer ear infections are a common sign of chronic allergy in dogs (caused by both food and environment)[13]. In cats, food-related itching often manifests as scratching of the head and neck area and general skin irritation; they may also lick their coat excessively, leading to broken hairs or bald patches[14]. In both cats and dogs, allergic skin symptoms can sometimes appear as various skin reactions, such as hives, swelling (angioedema), or hot spot dermatitis, but these are less common in food allergy[15].

Many pets with food allergies also exhibit gastrointestinal symptoms alongside skin problems. The most common are chronic or intermittent diarrhea, loose stools, increased need to defecate (more than ~3 times a day), flatulence, and sometimes vomiting[16]. In some pets, the only symptoms may be related to the intestines – for example, a cat may vomit frequently or a dog may have ongoing digestive issues without significant skin symptoms. For this reason, it is important to consider all symptoms: itching alone or diarrhea alone does not rule out food allergy. Allergies can also exacerbate each other's effects; for example, about 30% of food-allergic pets also have atopy[17], which can make symptoms more severe and diverse.

Most common allergens: A pet can basically become allergic to any protein present in food. In dogs, the most typical food allergens according to studies are beef, dairy products, chicken, wheat, and lamb, and to some extent also soy, corn, egg, pork, fish, and rice[18][19]. The prevalence is partly explained by the fact that these ingredients have been very common raw materials in dog foods[20]. In cats, beef, fish, and chicken stand out as causes of food allergies[18]. Wheat, corn, dairy products, and lamb are also reported allergens in cats, although less frequently[21]. According to Finnish veterinarians, the most common causes of food allergy are precisely the frequently used proteins: “beef, dairy products, chicken, lamb, fish, eggs, corn, wheat, and soy”[22]. It is important to note that grain allergy is clearly rarer in pets than allergy to animal-based proteins[23]. Gluten sensitivity to grains is possible in dogs (in certain breeds such as the wheat terrier), but in the majority of food allergy cases, the culprit is some meat-based ingredient.

Usually, allergies develop to foods that the pet has eaten for a long time – the immune system takes time to become sensitized. Therefore, even a young animal can have an allergy to a familiar food, and the allergy may not necessarily appear immediately after starting a new food[24]. Typically, food allergies begin in young adulthood (about 1–4 years old), but food allergy can also first appear in very young puppies (<6 months) and elderly pets[24]. Unlike atopy, there is no particular gender predisposition in food allergies[25]. Some breeds (e.g., German Shepherd, labrador, westie) have food allergies more commonly than average[10], but allergies can occur in all breeds.

The goal of the elimination diet is to find a diet for the pet that does not cause allergic symptoms, and to confirm the diagnosis of food allergy with a challenge test. Below is a step-by-step process recommended by veterinarians for implementing an elimination diet for a dog or cat[26][27]. The plan should be made together with a veterinarian to ensure the pet receives all necessary nutrients during the trial. Remember, extreme precision is required during the diet: even a small amount of forbidden food can ruin the results of the trial[28].

Diet selection: In an elimination diet, the pet is switched to eating only one new food that it has never eaten before. There are three options: (1) Special complete feed containing only one novel animal protein (and one carbohydrate)[29], (2) special food in which proteins are broken down by hydrolysis into such small pieces that the body does not recognize them as allergens[30], or (3) homemade diet from one new meat and one new vegetable or grain source[31][7].

Veterinarians may recommend, for example, hypoallergenic ready-made foods available at veterinary clinics (such as Royal Canin Anallergenic/Hypoallergenic, Hill's z/d)[30] or limited ingredient single-protein foods (such as venison-potato-based diets)[32]. However, many owners prefer to use natural foods, in which case a good option is homemade food or a high-quality single-protein complete diet from a novel protein source. The most important thing is that the chosen diet is completely new to the pet (allergens to which the pet is already sensitized must not be included)[7] and preferably a complete diet from which the animal receives all the necessary nutrients even in the long term[29].

As an example of natural and easy elimination diet food options, the Mr.Bones Dry BARF complete foods found in Muotitassu's selection can be mentioned, each containing only one animal protein source and a clearly limited composition. These air-dried foods are available in several flavor options such as: wild reindeer, turkey, mouflon, beef, chicken, and Iberico pig (wild boar) – all recipes contain 90% meat and 0% grain or artificial additives. The single-protein, limited content facilitates allergen management. Note: Always check the product description to ensure that no ingredient previously fed to the pet has been added to the food (e.g., some game-based foods may contain small amounts of beef raw materials, such as rumen, to improve flavor[35]). If necessary, you can confirm this with us.

Once a suitable diet food has been selected, proceed as follows:

1. Transition to new food: Change the pet's food gradually to the selected elimination diet food, preferably within a few days[36]. A sudden change in diet can itself cause digestive disorders, so a gradual transition helps avoid unnecessary symptoms. When the pet is completely on the new food, the start day of the elimination diet is recorded. (If the pet has had medication courses for skin or ear infections, the official start date of the diet is counted only when the skin has been treated and medications stopped[6].)
2. Diet phase – strict elimination for 8–12 weeks: Feed the pet only the selected elimination diet food for at least 8 weeks (in some cases 10–12 weeks if the symptom is only skin itching)[37][26]. Nothing else may be given to eat during this time. Pay attention to the actions of the whole family and environment: the pet must not secretly eat, for example, another dog's food, food scraps dropped on the floor, or pieces given by people. Put treats, chew bones, snacks, and supplements on hold – if necessary, you can reward the pet by giving small amounts of its diet food as a treat[38]. Also, for example, pills or vitamins that contain chicken liver or similar as a flavoring must be avoided[28]. The pet may only drink water (no milk or any added flavors)[39]. The idea of the strict diet is that the pet's body cleanses itself of previous allergens and any allergy symptoms can calm down. During the diet, it is advisable to keep a symptom diary – record the pet's skin condition, intensity of itching, ear condition, stool quality, etc. weekly so you can notice if progress occurs. Often, for example, skin itching begins to ease around 4–6 weeks, and after about 8 weeks the majority of food-allergic pets have responded positively to the diet[9]. If the symptom was only stomach upset, recovery may happen faster (in 2–3 weeks)[40]. Do not stop the diet prematurely, even if symptoms ease – it is important to complete the trial for at least the recommended time to ensure reliable results.
3. Exposure phase – return to the original food: Once the elimination diet has lasted long enough and the pet's symptoms have clearly improved, it is time to test for the presence of allergy. Veterinarians recommend performing a re-exposure: return the pet's original diet (i.e., the food/treats the pet ate before the diet) back to normal feeding[41]. Then observe whether the symptoms return. In allergic pets, symptoms typically recur within a few days of starting exposure, but in some cases it may take even 1–2 weeks before itching or other symptoms worsen again[42]. Record what and when the pet received during the exposure phase, and whether symptoms appeared. If no change occurs within a couple of weeks, the original food probably did not cause the symptoms and the diet trial is then negative (i.e., no food allergy is found at least with the tested diet).
4. Evaluation of results: If the pet's symptoms return during exposure, it confirms that it was a food allergy or hypersensitivity[42][43]. In this case, return to the elimination diet food and wait again for the symptoms to subside (this can take from a couple of weeks to a month)[44]. If, on the other hand, the symptoms did not return during exposure, the pet did not react allergically to the original food. In this case, it is worth considering other causes: many skin problems are caused, for example, by atopy or another food that was not tested. If the animal showed symptoms during the diet as much as before, food allergy is unlikely – it is advisable to consult a veterinarian about further investigations or a different type of elimination diet using another food[45][46].
5. Identification of the allergen: The above-described steps determine whether the pet has a food allergy or not. If the allergy is confirmed, the next question is to which substance the pet is allergic. Some owners do not find it necessary to precisely identify the culprit ingredient, but instead feed their pet only the diet that clearly suits it in the future (if it is a complete food, this can be done safely over a long period[47]). However, it is often useful to identify the allergen to allow more variety in the diet. This is practically done by food ingredient trials: the safe food used during the elimination diet is returned as the base, and one test ingredient is added at a time for about two weeks[48][49]. For example, start with proteins – give the pet, for instance, chicken alongside the elimination food for two weeks and observe if symptoms appear. If not, chicken is probably not the cause of the allergy; then try the next ingredient. If symptoms occur, a probable allergen has been found, and its trial is immediately stopped and the pet is returned to the safe food to wait for symptom relief before trying the next ingredient. By testing step by step, it is possible over time to map which meat, grain, and other ingredients the pet tolerates and which cause the allergy. The result helps to compose a permanent diet for the pet either from commercial hypoallergenic foods or homemade food with suitable recipes[50][51].

• Plan ahead and stay consistent. Finding a suitable elimination diet food may require effort. Discuss options with your veterinarian and choose a food that you can obtain sufficiently for the entire duration of the diet. Once the diet begins, strictly adhere to the rules – even a single “cheat snack” can cause symptoms in an allergic dog for weeks, undermining the reliability of the trial. Inform all family members about the importance of the diet so that no one feeds the pet secretly with other food.
• Keep a symptom diary. Record your pet's condition weekly (skin condition, degree of itching, hair loss, ear cleanliness, stool quality, vomiting, etc.). This way, you can objectively assess whether the elimination diet is helpful. Many pets need 6–8 weeks to recover from allergy symptoms[27], so be patient – quick results are not always visible. The diary is also useful for the veterinarian when reviewing the results.
• Treat accompanying problems. If your pet has itchy rashes, secondary bacterial or fungal infections, or for example an ear infection, it will likely need medication to treat these at the start of the diet. Allergic skin healing speeds up when infections are treated regardless of the condition. At the beginning of an elimination diet, the veterinarian often prescribes medications or medicated shampoos to relieve itching so that the pet feels better – these can usually be discontinued towards the end of the diet when it is seen whether the diet alone helps[52]. Similarly, parasite treatments (fleas, intestinal worms) should be kept up to date.
• Choose treats and chew bones correctly. During the diet, avoid all foods not included in the diet[28]. Offer your dog chew toys such as nylon or rubber toys instead of real bones. If you want to give treats, you can usually use the diet food itself: many animals like kibble or air-dried meat pieces as a treat when offered by hand. You can also use 100% dried meat of the same protein (without additives) – for example, if the diet is only venison, you can give small pieces of dried venison as a reward to keep the line. Mr.Bones treats offer good options of the same protein, so you can assemble a less restrictive set: Dry BARF food, treats, and snacks. Ask us for help if needed.
• Monitor your pet's weight and overall condition. An elimination diet can cause changes in your pet's weight, especially if the diet changes completely. Weigh your pet regularly and assess whether its ideal weight has been maintained – adjust the amount of food as needed under the guidance of a veterinarian. Also ensure that the diet food is complete nutrition (contains essential nutrients in the correct proportions). For example, in home-cooked and raw diets, it is important to add the necessary vitamins and trace elements according to a recipe prepared by an expert, so that a long elimination diet does not lead to deficiencies[31]. High-quality ready complete nutrition (such as veterinarians' hypoallergenic foods or high-quality single-protein dried BARF) is balanced and safe even as a several-month course.

Investigating allergy and atopy issues requires patience, but a successful elimination diet can bring significant relief to the pet's life. If the elimination diet confirms a food allergy, it is important to avoid identified allergens in the pet's diet going forward. Fortunately, there are now many options available for allergic pets: there are hypoallergenic specialty foods, natural foods based on novel proteins, and various protein sources (including rarer ones such as game, insects, horse protein, etc.) from which a safe diet can be composed. Discuss your pet's long-term nutrition with a veterinarian – the goal is that despite the allergy, the dog or cat remains symptom-free and receives a varied diet. And even if your own pet is not allergic to food, remember that variety in feeding is beneficial: it reduces the risk of sensitization to a single protein and also makes implementing possible future elimination diets easier if the pet is accustomed to eating several different proteins. As allergies become more common, it is important to take the pet's symptoms seriously and seek help – this way, together with the pet, the path leading to a healthier, itch-free daily life can be found.

Sources:

Kaarinan Veterinary Clinic: Home care instructions elimination diet – dog and cat[1][54][7][32][45]

FirstVet: Dog elimination diet and its implementation[29][40][41][44][48]

Merck Veterinary Manual: Cutaneous Food Allergy in Animals[9][18][10]

Clinical & Translational Allergy (2018): Atopic dermatitis in cats and dogs[8]

Evidensia Veterinary Clinics: Dog food allergy[22]

Muotitassu (Mr.Bones Dry BARF product descriptions)[33][34]

Muotitassu (Mr.Bones 100% venison treat)[53]

[1] [5] [6] [7] [27] [32] [36] [37] [45] [46] [49] [50] [51] [54] Home care instructions for elimination diet – dog and cat - Kaarinan Veterinary Clinic Ltd

https://kaarinanell.fi/ajankohtaista/ohje/kotihoito-ohjeeliminaatiodieetti-koira-ja-kissa-2/

[2] [3] [26] [28] [29] [30] [31] [38] [39] [40] [41] [42] [43] [44] [47] [48] Dog elimination diet and its implementation | FirstVet

https://firstvet.com/fi/artikkeleita/kuinka-toteuttaa-eliminaatiodieetti-koiralle

[4] [9] [10] [12] [13] [15] [16] [18] [19] [20] [21] [24] [25] Cutaneous Food Allergy in Animals - Integumentary System - Merck Veterinary Manual

https://www.merckvetmanual.com/integumentary-system/food-allergy/cutaneous-food-allergy-in-animals

[8] [11] [14] Atopic dermatitis in cats and dogs: a difficult disease for animals and owners | Clinical and Translational Allergy | Full Text

https://ctajournal.biomedcentral.com/articles/10.1186/s13601-018-0228-5

[17] Dog Food Allergies vs Seasonal Allergies - Princess Animal Hospital

https://www.princessanimalhospital.com/resources/blog/september-2020/dog-food-allergies-vs-seasonal-allergies

[22] Dog food allergy - Evidensia Veterinary Clinics

https://evidensia.fi/hoitovinkit/koiran-ruoka-aineallergia/

[23] Does my dog have a food allergy? Symptoms and common allergies ...

https://saraderm.fi/onko-koirallani-ruoka-aineallergia-oireet-ja-yleisemmat-allergian-aiheuttajat/

[33] [34]  Dry BARF Iberico pork – grain-free complete nutrition for dogs - Muotitassu

https://muotitassu.fi/collections/uutuudet/products/mr-bones-dry-barf-iberian-sika-koiralle

[35]  Dry BARF wild venison – grain-free complete nutrition for dogs - Muotitassu

https://muotitassu.fi/collections/uutuudet/products/mr-bones-barf-villi-peura

[52] Five tips for a successful elimination diet for dogs - Aures skin

https://www.aureselainlaakarit.fi/viisi-vinkkia-koiran-eliminaatiodieetin-onnistumiseen/

[53]  Mr.Bones – Muotitassu