How to conduct a food trial: Dog


  • If your dog has itchy skin, diarrhoea or symptoms of IBD, your vet may want to check whether they're allergic to something in their food (conduct a food trial).
  • This involves feeding a specially made food that your dog won’t be allergic to and absolutely nothing else for a set amount of time.
  • If your dog’s symptoms improve or go away completely during the trial, they were probably allergic to something in their food. If their symptoms stay the same, it’s unlikely that their food is the only cause of their symptoms.
  • Most food allergies are caused by proteins such as beef, chicken or lamb, but some are caused by ingredients such as wheat.
  • Many dogs are allergic to more than one thing.

Step-by-step guide

  • Your vet will recommend a special food that you will need to feed your dog for at least 6-12 weeks.
  • Do not allow your dog to eat anything other than their special diet (this means no human food, dog treats or dental sticks).
    • Your vet or vet nurse will be able to give you some tips on how to make treats out of the special food so that you can still give your dog some variety if necessary.
    • Don’t add anything to your dog’s food without speaking to your vet beforehand, even if they refuse to eat it.
  • Your dog can drink water as usual, but shouldn’t be allowed anything else (such as milk).
  • Keep a diary to record your dog’s symptoms each day.
  • If your dog accidentally eats something other than their recommended diet, make a note of what and when, and monitor for any symptoms. Make sure you tell your vet so they know the food trial was affected.
  • At the end of the trial, your vet will let you know whether the diet trial has been successful and talk about the next steps


  • If your dog eats anything else during their food trial, they might react and you may need to start the process again.
  • If your dog takes supplements, you will need to check with your vet that they are ok to continue.
Published: September 2020

Written by vets and vet nurses. This advice is for UK pets only. Illustrations by Samantha Elmhurst.