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Feeding an Exclusion Diet Fact Sheet

Dietary allergy or intolerance can underlie a number of diseases. Feeding an exclusion diet is an important part of diagnosis and management.

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What is an exclusion diet?

An exclusion diet is a diet designed to remove ingredients that a patient has previously encountered. Food can trigger clinical disease in a number of ways, including food allergy, toxicity and intolerance (e.g. lactose [milk sugar] intolerance). Clinical signs of dietary sensitivity include vomiting, diarrhoea, itchy skin, ear disease, coughing and wheezing, amongst others.

Why feed an exclusion diet?

We recommend exclusion diet feeding for two reasons: diagnosis and treatment. The diagnosis of food sensitivity requires the demonstration of improvement of signs when the food is withdrawn and return of signs after feeding the food again. If a patient gets better when on an exclusion diet, long-term feeding of an appropriately balanced diet may be a very effective treatment.

How long do we feed a diet for?

For the purpose of diagnosis, we typically recommend at least 4 weeks of exclusion diet feeding. Some authorities have suggested up to 12 weeks may be necessary to completely exclude a dietary sensitivity from possible causes of disease.

What foodstuffs can cause dietary sensitivity?

Theoretically, any foodstuff or ingredient (including additives) can trigger a reaction. In pets in the UK, however, we tend to avoid commonly encountered ingredients in exclusion diets, such as chicken, beef, lamb, soya and wheat.

What can we feed?

There are two options: home-cooked food and proprietary diets.

  • Home-cooked food has the big advantage that we can be certain what is in it.
  • Proprietary foods are formulated to be balanced for long-term feeding, but have the disadvantage that they inevitably are less ‘exclusive’ than home-cooked diets.

We generally recommend that the diagnostic phase of an exclusion diet (typically the first 4 weeks) be based on a home-cooked regime. We also recognise that this is not always easy, depending upon an owner’s life-style.

For both home-cooked and proprietary diets, we try to choose a combination of a single novel carbohydrate and a single novel protein neither of which we believe the patient has previously eaten.

Carbohydrate options

  • Boiled potato
  • Porridge oats (cooked in water)
  • Boiled rice
  • Polenta
  • Tapioca

Protein options

  • Turkey
  • Pork
  • Rabbit
  • Venison
  • Fish (e.g. salmon, cod, capelin)

How much should I feed?

It is impossible to give accurate amounts to feed an individual, because there are so many variables, not least the underlying disease. For home-cooked food we normally recommend 1/3 cooked protein: 2/3 cooked carbohydrate, fed to appetite in 2-3 meals daily. Amounts can be adjusted according to intake and body weight. Occasionally, we will add some vegetable oil to provide extra calories.

This regime is adequate for the diagnostic phase of the feeding trial. For longer term feeding, a more nutritionally balanced diet must be designed; sometimes a proprietary diet is the best option at this stage.


What should I give to drink?

Plain water only should be offered. Milk etc. can be a culprit food.


But my dog is a scavenger!

Dogs, particularly, are scavengers by nature. They will hoover up everything that might be food. This behaviour must be prevented for an effective exclusion diet trial. Times of particular difficulty are when there are young children or visitors in the house, when there are multiple pets, during walks when off the lead and during social events, e.g. parties. Use of a short lead, constant supervision and, occasionally, a muzzle may be necessary.

What about his treats/ vitamins/ supplements?

Whilst a balanced diet is very important for long-term health the smallest amount of a triggering food can cause clinical signs, which may often be quite dramatic (think of peanut allergies in children). We therefore advise the strictest of exclusions, especially in the diagnostic phase of any exclusion diet trial. All treats, animal-based chews, vitamin supplements etc. should be withdrawn. Note that some medications may contain animal protein in the formulation: ask your clinician about this if you are concerned. Many pets consider any food given outside normal meal times a treat, so normal treats may be substituted with a small morsel of the exclusion diet itself.

When should I report back?

We typically ask for a telephone report after 2 weeks, although we may ask you to ring sooner if there are results pending. If your pet refuses to eat the new food, or is showing worsening signs, or you are worried for any other reason, please call.

If you have any further questions about diets you should speak to your veterinary surgeon who will be able to discuss this with you more fully.

If you are concerned about the health of your pet you should contact your veterinary surgeon.


Related factsheets

Diarrhoea in dogs and cats

Vomiting in dogs and cats

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