When a dog scratches constantly, develops dermatitis or suffers recurring intestinal upsets, the cause is often on the plate. The elimination diet — also called the exclusion diet — is the main tool the vet uses to work out whether an allergy or food intolerance lies behind these symptoms, and to identify the ingredient responsible. Let's look at how it works, how long it lasts and why choosing a single protein makes all the difference.
Adverse reactions to food are more common than people think, and food is one of the main causes of allergies and food intolerances in dogs. The problem is that their symptoms resemble those of many other conditions, and there's no truly reliable blood test to diagnose them. The elimination diet remains, to this day, the reference method: simple in principle, but requiring method and discipline to give clear answers.
The elimination diet comes into play when food is suspected to be at the root of a chronic disorder. The typical signs of a food allergy or intolerance are:
These symptoms can have many different causes — parasites, environmental allergies, other skin diseases. That's why the first step is always to talk to the vet, who will rule out the other possibilities and decide whether and when to start an elimination diet. It's a process that should be set up and followed with a professional: this article is here to help you arrive prepared, not to replace the consultation.
The logic is as simple as it is strict: for a few weeks you feed the dog exclusively with a food containing ingredients it has never eaten before — or, at any rate, pared right back — and you observe whether the symptoms improve. The diet unfolds in two phases.
1. Elimination phase. Together with the vet, you choose a food based on a single protein source, ideally new to that dog (see below). For the whole duration of the phase — several weeks — the dog must eat only that: no other kibble, no different wet food, no treats, no table scraps, no "stolen" mouthfuls. Even a single break from the rule can skew the entire experiment. During this period you note the progress: as a rule, if the cause is dietary, the symptoms start to recede within the first few weeks.
2. Reintroduction (or challenge) phase. When the dog has clearly improved, you reintroduce the previous ingredients, one at a time, to see which one makes the symptoms return. If reintroducing a particular food brings back the itching or intestinal upsets, we've identified the culprit: that ingredient is to be avoided for good. This second phase is what turns the diet from mere relief into a genuine diagnosis.
Here lies the heart of it all. A food allergy is a reaction of the immune system to a protein it recognises as an "enemy" — most often an animal protein the dog has eaten for a long time (chicken, beef, sometimes dairy derivatives or eggs). Two concepts are fundamental for a well-run elimination diet:
Single protein. It means a food with one animal protein source, with no mixing. The fewer proteins there are in the recipe, the fewer potential allergens the dog has to deal with and the easier it is to understand what it's reacting to. A food that combines chicken, beef and fish is unusable in an elimination diet, because it doesn't allow you to isolate the single variable.
New (novel) protein. It's a protein the dog has never come into contact with: if it has never eaten it, its immune system has had no chance to "learn" to react to it. Proteins such as horse are often chosen for exactly this reason, in dogs that have always eaten the more common meats.
The success of the diet therefore depends largely on the quality and "cleanness" of the food chosen: a single, clearly stated protein, and an ingredients list as short and transparent as possible. Knowing how to read the packaging well is crucial, because many "single-protein" products actually hide other animal sources among the minor ingredients: our guide on how to read dog food labels helps you spot them.
The elimination phase typically lasts six to eight weeks, but in cases with mainly skin symptoms it can take longer — even ten or twelve weeks — because the skin heals slowly. It's a process that takes patience: don't be discouraged if the improvements are modest in the very first weeks.
What to expect, if food really is the cause: a progressive reduction in itching, healthier skin, fewer ear infections, more formed stools and an altogether calmer dog. If, on the other hand, after a diet run with absolute rigour nothing changes, that's valuable information: it means the cause has to be sought elsewhere, and the vet will point you towards other investigations. In either case, a well-conducted elimination diet is never time wasted.
The number-one enemy is contamination: the morsel given by the child, the scrap that's "hardly anything", the training treat, the crumbs picked up on the walk, even a flavoured toothpaste or an unapproved supplement. Each of these small exceptions can introduce the offending protein and ruin weeks of work. During the elimination phase the rule is just one and it must be explained to the whole family: nothing but the chosen food.
Other frequent mistakes: stopping the diet too soon, discouraged by the slowness of the results; changing the food halfway through; and skipping the reintroduction phase altogether, thereby giving up knowing which ingredient to avoid in future. Choosing a supermarket "hypoallergenic" food on your own, without really checking its ingredients, is another classic misstep. If you'd like a broader picture of the most common dietary mistakes, we've gathered the main ones in the 5 dog feeding mistakes.
Pappa Fresh is built on exactly the logic that makes an elimination diet effective. Our recipes are single-protein: one animal source per recipe — including proteins such as horse, often "new" for many dogs — with no mixing, no preservatives and no superfluous ingredients. The ingredients list is short and transparent, so you know exactly what your dog is eating: the ideal starting point both during the elimination phase and for long-term maintenance once the safe protein has been identified.
Each recipe is formulated by a vet and is complete and balanced, so it can become the stable diet of a sensitive dog even after the diagnosis. And being shelf-stable fresh food, it keeps without a freezer and arrives in practical portions, easy to manage with the rigour an elimination diet demands. To find the protein source best suited to your dog and the correct portion for its weight, start with our calculator: in a few minutes it builds the tailored plan and lets you try it with the trial box.
Allergies or intolerances? Find the right single protein and the correct portion for your dog.
Calculate your dog's planThe elimination diet is the most reliable tool for finding out whether your dog's chronic troubles — itching, dermatitis, ear infections, intestinal upsets — depend on food. It works in two phases, elimination and reintroduction, generally lasts six to eight weeks and rests on an iron rule: during the elimination phase the dog eats only the chosen food. The key to success is the quality of that food: a single protein, ideally a new one, with a short, transparent ingredients list. Always set up the process with your vet — and choose a food that makes it simple to follow it through to the end.
This is precisely the idea the single-protein Pappa Fresh recipes are built on: a single protein, no preservatives, simple ingredients and portions calculated for your dog. For a few more answers, take a look at our frequently asked questions too.
Veterinary surgeon, medical director of the Clinica ARS Veterinaria di Modena. He works every day on canine nutrition, prevention and wellbeing, with a particular focus on food allergies and intolerances and the management of elimination diets.
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