Hope you get some answers from the doctor.

Have you ever tried giving him aloe vera juice? Not the sugary drink from the supermarket but a pure juice you can buy from the chemist and you give them a dose of 5ml for it every day. My DS has shocking ezcema but we found the aloe vera juice works exceptionally well. I know different things seem to work for different people but it is worth a shot. It does something to the digestive system as well so it might help with food allergies.

Good luck