Diet and health
Food Allergies vs Food Intolerances in Pets
The two are often confused, are diagnosed differently, and true food allergy is far rarer than marketing around 'hypoallergenic' diets suggests.
Allergy versus intolerance
A true food allergy is an immune reaction, most often to a specific protein, and typically causes skin problems — itching, ear infections, recurrent skin infections — more than digestive signs. A food intolerance is a non-immune reaction, often to fat content or a specific ingredient, and usually shows up as vomiting or diarrhoea. The distinction matters because the diagnostic approach differs.
Diagnosis is a diet trial, not a test
There is no reliable blood, saliva or hair test currently validated for diagnosing food allergy in dogs or cats, despite such tests being marketed directly to owners. The accepted method is an eight-to-twelve week elimination diet using a novel or hydrolysed protein source under veterinary guidance, followed by a controlled reintroduction of the original food to confirm the reaction.
Why an at-home trial usually fails
Elimination trials fail most often because of accidental exposure — a flavoured medication, a shared treat, another household member feeding table scraps — rather than because the diet itself was wrong. Strict compliance from everyone in the household for the full trial period is what makes the result trustworthy.
- No treats, flavoured chews or table scraps outside the trial diet
- Check flavoured medications and supplements with your vet during the trial
- Keep a symptom diary throughout so the reintroduction result is easier to interpret
This needs veterinary involvement
Choosing and running an elimination diet, ruling out other causes of itching such as fleas or environmental allergy, and interpreting a reintroduction reaction all benefit from veterinary guidance — do not self-diagnose a food allergy from an online symptom list and switch diets repeatedly, which makes any future trial harder to interpret.