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From VetChef vets and nutritionists

Elimination (exclusion) diets

What is an elimination diet?

Also referred to as exclusion diet, an elimination diet is made up of limited and carefully selected foods in order to test whether or not a pet has a dietary allergy or intolerance.

When are they used? Vets may recommend them where pets have possible allergies affecting the gut, the skin, or both.

Some situations where elimination diets might be used:

  • Chronically itching skin where food allergies are suspected and other conditions have already been ruled out.

  • Recurring ear infections (may sometimes be caused by food allergies).

  • Chronic diarrhoea or vomiting where other conditions have already been ruled out.

Types of Elimination Diets

Commercially prepared/hydrolysed diets

  • Hills z/d

  • RCW Anallergenic

  • Purina HA

  • Specific CDD-HY

These products contain proteins that have been chemically broken down in such a way that the immune system should not be able to recognise them.


  • Convenient

  • Especially useful if you do not know the dietary history of a pet and cannot easily select the right ingredients for a home-cooked trial (see later)

  • Complete and balanced from the start


  • Palatability (taste) can be an issue for some pets, especially those that are already off their food or nauseous

  • There are still a large number of ingredients (albeit hypoallergenic) so some pets may still react

  • A small number of pets may still react to the base protein even though it is broken down

  • As hydrolysed foods are produced in larger factories, there is a small possibility of cross-contamination

  • Some pets have allergies to by-products or storage mites associated with dry foods (tinned option may also reduce this risk)



  • Usually initially composed of two ingredients only

  • Gold Standard approach

  • No risk of cross contamination or other contributing factors

  • Less ingredients in total (less potential allergens)

  • Often slightly higher digestibility (may be of benefit in gut cases)

  • Palatability of home-cooked is usually better. Some pets will refuse commercially prepared hydrolysed diets.


  • Not usually balanced and complete to start with (although balance can be achieved quickly with VetChef recipes when required)

  • Time consuming as it requires regular cooking by the owner

  • Cost depends on the ingredients required. For some pets where very unusual/expensive proteins are needed then home-cooked may be substantially more expensive

When should I start an elimination diet?

You should only start a home-cooked elimination diet under the direction of your vet or nutritionist. It is also vital that your pet is checked over first to ensure that all underlying infections are under control as failure to control these can confuse the results of an elimination trial. For example, it may well look as though the trial is not working if existing infections continue to cause itching or diarrhoea.

How should I start?

Any sudden change of diet can cause (or worsen) diarrhoea or other gut signs so it is important to introduce exclusion diets slowly. In most cases we would advise making a batch of the food and gradually changing from the previous food over 1-2 weeks. Do this by adding a little more of the new recipe to the meal each day.

Can I feed treats or other things in addition to the elimination diet?

No, exclusion diets work because they reduce the number of potential allergens that your dog is exposed to. Adding treats or additional ingredients may cause reactions, making it difficult to tell whether or not it has worked.

Ideally feed ONLY the ingredients that are listed in the elimination diet for the full length of the trial.

You CAN keep some of their daily meals aside and feed separately as treats on walks or for training.

How long does an elimination diet trial take? In some cases the response can be rapid (within a week or two), but for other pets improvement is slower.

If there has been no notable improvement in 10 weeks we would consider that the trial has not been effective. You should not continue an unbalanced elimination diet for longer than 12 weeks in total.

What if my pet gets worse on the trial?

You should keep in close contact with your primary vet during any diet trial. If your pet is vomiting, has worsening diarrhoea, is losing weight or is in any other way responding negatively to the new diet, you should contact them in the first instance.

VetChef can also help you make adjustments to calories if your pet appears to need more or less (and your vet has checked your pet is still otherwise well).

How do I monitor for a ‘positive’ response? Consider using a poo or itch scale (depending on the symptoms your pet has). For some dogs the improvement will be complete and itching/diarrhoea might resolve completely, but partial responses are still important. Itch and poo scoring can help you to keep track of smaller or partial improvements.

Small improvements are still important as they may still reduce the frequency of flare-ups or requirement for medication.

Link to stool chart -

Link to itching scale -

What happens if I see a positive response?

If your pet’s symptoms improve, this suggests that food allergies are playing a part in their disease (skin or gut).

It is common that we would recommend continuing an exclusion diet for a few weeks after the positive response is seen in order to allow residual inflammation to resolve.

How do I get my pet back to a balanced diet? Once a pet has stabilised on an exclusion diet of any kind (commercial or home-cooked), they are then ‘challenged’ with new foods. You can do this ideally with one ingredient at a time or you can try introducing commercial foods that are similar to the ingredients that your pet has been eating during the elimination trial.

  • One ingredient at a time:

When introducing a new ingredient we only need to add a little of the new ‘test’ food to each meal. Making large sudden changes to ingredients without allowing any time to adjust is likely to cause an upset stomach regardless of allergy, so it’s important to only use small amounts.

We’d recommend adding a teaspoon daily (small dogs) or tablespoon daily (medium/large dogs) to the meal. This is plenty to test for allergies without upsetting their stomach.

Continue this ingredient for 1-2 weeks. If there is no negative response, make a note. You can then stop this ingredient and try another. You will eventually form a list of ingredients that you know that your dog is tolerant/allergic to.

Some negative responses are rapid (within a day) but other types of reactions to new foods can take 1-2 weeks. Don’t try more than one ingredient per week.

  • Which foods should I introduce?

Ideally choose foods that your pet has had minimal exposure to in the past. It may also be helpful to plan where you want to ‘end up’. For example, if you want your pet to end up on ‘X-Brand Venison and Green Pea recipe’ then it would be sensible to look at trialling the ingredients that are in this product.

VetChef has a range of complete recipes that are based on the same limited ingredients as the elimination diets to help with this step.

  • What happens in the long term?

For most pets, once there has been a good period of respite from symptoms, it is possible to return to a complete and balanced recipe or a complete food; whichever is preferred!

Pets with IBD are never ‘cured’, so it is possible that there will still be flare ups at times of stress or where pets eat foods that they are not supposed to (or are allergic to). Pets with IBD tend to do better on consistent foods that do not change daily but you may still be able to gradually change between non-allergenic foods if needed.

Can I use an elimination diet in a puppy?

Yes but make sure any recipe fed to a growing puppy is complete and balanced the whole time. It is not safe to use an unbalanced elimination diet in puppies. At VetChef we have created limited-ingredient but complete diets that are safe to use in growing dogs.

If you need an elimination diet for a puppy but cannot see one that suits, please let your VetChef advisor know and we will create one for you.

Some existing prescription hydrolysed diets are also suitable for puppies (e.g. Purina HA). Contact individual companies or your vet to find out more about these products.

Are there circumstances where I should not use an exclusion diet?

For some pets unbalanced exclusion diets are not safe. For these pets, you will instead need to choose a balanced but limited-ingredient diet, or use a commercial product recommended by your vet.

Pets who may need to skip straight to balanced limited ingredient diets:

  • Puppies that are still growing

  • Dogs with some concurrent conditions (e.g. renal failure)

  • Dogs whose previous diet was not balanced (these pets need to replenish their nutrient supplies and should not continue on an unbalanced diet)

  • Dogs that have severe or very long-standing symptoms such as drastic weight loss or those already showing signs of nutrient deficiency like a poor/brittle coat.

  • Any other pet where your vet has advised that a balanced diet is needed right away

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