I'm so sorry to hear this. As you may remember,my Pearl also has this but she would only break out on her lips. With her it seems to be a food allergy and since she's been eating Innova Evo dry she hasn't had any more breakouts. Now of course she's dealing with liquid diarrhea though.

I wish I knew what to tell you but I don't know much about this disease. Some cats need to be put on prednisolone or have the depo shotsto help control it. I hope that you'll be able to find the right solution for Leo. I'll keep him in my thoughts and prayers. Please take care.