Your veterinarian will examine your cat, and ask you for information regarding your cat’s diet, the symptoms you have seen, when you first noticed them and what changes you have observed. You will likely also be asked whether you have observed any changes in your cat’s behavior.
Your veterinarian will conduct a full physical examination and if he thinks that a food allergy may be a cause of his symptoms, he will ask you about the food that your cat consumes, as well as how much he eats per day and for how long he has been eating that particular food. Your veterinarian may recommend a complete blood count, serum chemistry analysis, urinalysis and evaluation of a stool sample to determine if there is an underlying illness that is causing the symptoms your cat is experiencing. He may take a sample of your cat’s skin cells in order to view them under a microscope for mites, fungus or bacteria; should none of those be present, it can help narrow down the reason for your cat’s symptoms. Ear infections and gastrointestinal issues are often present when cats are experiencing allergies, therefore, your veterinarian will look to see if these are issues in your cat.
Should your veterinarian determine that your cat may be experiencing a food allergy, he will work with you on developing an elimination diet for your cat. An elimination diet is one that is simple; often it will be home-cooked so that there will not be any hidden ingredients that you are not aware of. In the elimination diet, typically only one protein will be given. If the main protein in your cat’s usual diet is lamb, your veterinarian will recommend avoiding that in the elimination diet.
Within 3-4 weeks (on average) you should see some improvement in your cat’s symptoms. As you are reintroducing foods, should the food be one that your cat is experiencing an allergy to, you will notice a reaction pretty quickly (within a few hours to ten days). If your cat no longer has symptoms when on the new diet, but when his old food is reintroduced he again experiences symptoms, the food allergy is confirmed.