There are many options to address this suspicion. The most accurate way to pinpoint sensitivity to a certain protein is a diet trial. This implies an extremely restricted diet for a period of time, usually 10-12 weeks, to determine if the pet’s symptoms are related to diet. Following the trial, we add in foodstuffs one at a time and when symptoms return, this tells us what the problematic ingredient is.
The best type of food trial, which cannot be given long term as it is not balanced, is a protein source that your pet has never eaten combined with a starch and cooked at home, for example pork and sweet potato. Why never eaten? The immune system needs to have encountered a protein to develop antibodies to it, so any allergy will be to something the pet has eaten before. The second best option is a hydrolysed diet. This diet is transformed so that the proteins will not react with an animal’s immune system, similar to hypoallergenic baby formula. The last option is a commercial unique protein source diet, such as venison or duck. It is important to ask questions about residue testing and cross-contamination, to be sure that the fish diet you are buying has not been contaminated by the chicken diet that was made beforehand.
Please ask your veterinary team for more information about how to make the best choice for your pet.