Cytopoint is prescribed for the treatment of environmental allergies. Food has no effect on environmental allergies and where your dog has two serious medical conditions besides the allergies, I think anyone advising you over the internet to do anything other than what the treating veterinarian recommends would be irresponsible.
I would refer you back to the veterinarian to discuss your options regarding diet changes and allergy treatment. Or, have the veterinarian refer you to a specialist if he thinks this would help.
