Last Updated: 10/09/2026
Elimination Diet Trials for Dogs: How to Run One Properly
Everything you need to know to run a dog elimination diet trial properly, including the mistake that ruins many trials.
Author: Dr Gillian Hill BVSc (Hons)
Reading Time: 4 minutes - short read
If your dog's been scratching, chewing their paws or dealing with runny poos for weeks, your vet may have suggested an elimination diet trial, usually using a novel protein or hydrolysed dog food. It's a genuinely useful diagnostic tool, but only if it's run properly. Here's what an elimination diet trial involves, and the one mistake that commonly trips pet parents up.
An elimination diet trial means feeding your dog one exclusive novel protein or hydrolysed diet, with nothing else at all, for 8 to 12 weeks. Trials rarely fail because of the diet, they fail because treats, flavoured medication or scraps sneak in and undo weeks of progress. Don't stop early, and make sure to rechallenge with the old diet afterwards if your vet advises it.
Does my dog need an elimination diet trial?
An elimination diet trial is usually recommended when your vet suspects a genuine food allergy or intolerance behind ongoing itchy skin, ear infections or digestive upset, not just because your dog seems fussy. Our guide on does your dog have a food allergy covers the signs in more detail.
Most itchy dogs are actually dealing with environmental allergies or fleas, not food. Where food is the cause, beef, dairy, chicken and wheat are the most commonly reported culprits (Mueller et al., 2016).
There are two main ways to run the trial, a novel protein your dog's never eaten, or a hydrolysed diet with proteins broken down too small to trigger a reaction. Hydrolysed diets are considered the gold standard. Our hypoallergenic diets guide compares both.
What's the most common mistake with elimination trials?
In clinic, trials rarely fail because of the diet itself, they fail because of everything that sneaks in around it.
Owners feed the trial diet properly at mealtimes, then hand over a dental chew, a spoonful of peanut butter for a tablet, a flavoured parasite preventative, or a lick off the kids' plates. Any of these can contain a protein your dog hasn't had, or worse, one they're already reacting to, and even small amounts can undo weeks of progress (Freeman, 2022). The rule is strict: control everything that goes into your dog's mouth, treats, chews, medicationss, supplements, scraps and toothpaste included, unless your vet has cleared it. Your vet may recommend switching to a topical parasite preventative, or one that contains no animal proteins for flavouring, for the duration of the trial.
How do you run a novel protein elimination trial properly?
Feed one exclusive diet, and nothing else, for 8 to 12 weeks.
- Choose the right diet with your vet, a novel protein or hydrolysed option (our hypoallergenic diets guide compares the two).
- Cut out everything else, no treats, chews, flavoured meds or scraps unless approved. You may need to separate dogs for feeding in a multi-pet household, and use gates to prevent your dog accessing family foods.
- Feed exclusively for 8 to 12 weeks, extending this lifts diagnostic sensitivity above 90% (Tham, 2024). Digestive-only trials can be shorter, around 3 to 4 weeks (Freeman, 2022). See our sensitive stomachs guide for more information on digestive sensitivities.
- Keep a symptom diary tracking signs - itching, ears, stools and coat. A weekly photo helps spot gradual improvement.
- Don't stop early, even with fast improvement.
- Rechallenge if advised, reintroducing the old diet to confirm the diagnosis. This means feeding it again for one to two weeks, watching for symptoms to flare back up.
What are the signs the trial is working?
In truly food allergic dogs, steady improvement including less itching, fewer ear flare-ups, firmer stools, a better coat, over the first few weeks is a good sign. The most common mistake we see is owners giving up by week three or four, as improvement is usually gradual. When related to food, gastrointestinal symptoms usually improve within 2 weeks on the trial while skin signs take longer - about 90% of dogs and cats will show improvement in skin complaints within 8 weeks but 5% of dogs may take up to 13 weeks to improve (Olivry 2015).
See your vet if there's no change by 8 weeks - if the elimination trial has been run properly, this likely means there's another reason for the signs, other than food allergies. If symptoms worsen, or you notice any new signs like vomiting, weight loss or skin infections at any time during the elimination trial, see your vet ASAP as these may need their own treatment.
Which novel proteins are used in dog food?
Common novel proteins include kangaroo, venison, duck, rabbit and, increasingly, insect protein, though what counts as "novel" depends on your dog's history. Kangaroo is popular in Australia simply because most dogs haven't encountered it.
Our review of the Instinctive Bite single protein range, including kangaroo and duck options, and our novel protein diets guide are good next reads.
FAQs
An elimination diet trial is a diagnostic tool, not just another food to try. Run properly, one exclusive diet for 8 to 12 weeks with nothing else sneaking in, it can finally answer whether food is behind your dog's symptoms. The treats and flavoured extras are usually what trip owners up, so that's the part worth being strictest about.
References
Mueller RS, Olivry T, Prelaud P. Critically appraised topic on adverse food reactions of companion animals (2): common food allergen sources in dogs and cats. BMC Veterinary Research. 2016;12:9. https://pubmed.ncbi.nlm.nih.gov/26753610/, accessed 8/9/2026
Freeman LM. Think Your Pet has a Food Allergy? Eliminating Mistakes in Elimination Diet Trials. Petfoodology, Cummings School of Veterinary Medicine at Tufts University. Published 4 April 2022. https://sites.tufts.edu/petfoodology/2022/04/04/think-your-pet-has-a-food-allergy-eliminating-mistakes-in-elimination-diet-trials/, accessed 8/9/2026
Tham HL. Elimination Diet Trials: Steps for Success and Common Mistakes. Today's Veterinary Practice. Published 14 June 2024. https://todaysveterinarypractice.com/dermatology/elimination-diet-trials-steps-for-success-and-common-mistakes/, accessed 8/9/2026
Hydrolyzed Diets. NC State University College of Veterinary Medicine Veterinary Hospital. https://hospital.cvm.ncsu.edu/services/small-animals/nutrition/hydrolyzed-diets/. Accessed 8/9/2026
Olivry T, Mueller RS, Prelaud P. Critically appraised topic on adverse food reactions of companion animals (1): duration of elimination diets. BMC Vet Res. 2015 Aug 28;11:225. https://pubmed.ncbi.nlm.nih.gov/26310322/, Accessed 8/9/2026
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History
Our experts continually monitor the health and wellness space and we update our articles when new information becomes available.
Tue 8 Sep 2026
Written by Dr Gillian Hill BVSc (Hons)Dr Gillian Hill BVSc (Hons)
Veterinarian
Dr. Gillian graduated from the University of Sydney in 2005 with a Bachelor of Veterinary Science. She worked in a number of small animal clinics, before joining the Pet Circle Vet team in 2020. Dr. Gillian has special interests in ultrasonography, surgery and behaviour. Her favourite part of being a vet is being an advocate for the animals. She loves helping owners to make the best, evidence-based decisions for their pets, and seeing the beautiful bond that people have with their fur-babies.
