How to run an elimination diet for your cat
If your cat has ongoing itching, vomiting, or digestive problems, a food allergy may be suspected. The most reliable way to find out is by running an elimination diet trial.
What is an elimination diet?
An elimination diet is a simple test:
Feed your cat a very limited diet that avoids common allergens
Wait to see if symptoms improve
Gradually reintroduce foods to see if symptoms return
If symptoms improve and then come back when a food is reintroduced, this strongly suggests a food allergy.
Choosing the right diet
Most elimination diets use either:
Novel protein diets (e.g. rabbit or venison)
Hydrolysed protein diets (where proteins are broken down so they are less likely to trigger a reaction)
Your vet can help you choose the most appropriate option, especially if your cat has complex or severe symptoms.
A key point:
Choose a food your cat has not eaten before, and keep the diet as simple as possible.
Be strict (this is the hardest part).
For the trial to work, your cat must eat only the chosen diet.
That means avoiding treats, human food, flavoured medications, supplements (unless approved.) Even small amounts of other foods can affect the results.
If you have more than one cat, keeping diets separate can be tricky. See my guide to managing food allergies in multi-cat households here.
How long does it take?
Most trials last 6–8 weeks.
Digestive symptoms may improve within a few weeks. Skin symptoms often take longer.
If there is no improvement after trying one diet, your vet may suggest trying a different one.
The “challenge” step
If your cat improves, the next step is to confirm the allergy. This is done by reintroducing the old food, or
adding one ingredient at a time.
If symptoms return (often within a few days), this helps identify the trigger. Some owners prefer not to do this step if their cat is doing well, as it can feel counterintuitive to risk symptoms returning.
After identifying a trigger
Once you know which foods cause problems:
- avoid those ingredients
- choose a suitable long-term diet
Many cats do very well once the trigger is removed.
A note on allergy testing
Some tests claim to diagnose food allergies using blood, saliva, or hair samples. These are not considered reliable. This is why vets don’t routinely offer these tests. An elimination diet remains the most accurate way to diagnose a food allergy.
Final note
Elimination diets require patience, but they are the most effective way to understand what your cat can safely eat.