A fever, discoloration and itching can result from an acute(immediate or recent)allergy/immune sysytem reaction. The immune system always comes into play with allergies and NOT JUST illnesses, per say. An allergy can make any creature/person very sick. This can be from anything! Any chemical changes in the animals' envirnmt. New or different foods? Table scraps are NOT to be given! This is only one good reason. New laundry soap? Perfumes? Home sprays around the house? Best thing to do is to get to the vet ASAP. Keep in mind what I said about the table scraps for future reference because in the long run, this kind of food (human style, esp. Baked goods) do not help a dog at all! Famous for causing pancreatic damages. I hope this helps.
