Sorry your little one is suffering through this My DD#1 was the same, we had her allergy tested at 1 year (they wouldn't see us before she turned 1) and she was allergic to dairy, fish and egg. Did the allergy testing you had done come up with anything?
We also saw a dermatologist and were prescribed an ointment called Advantan Fatty Ointment (going by memory, I'm sure that's that name though). I always found that the creams dried her skin and we also used pretty much everything on the chemists shelves (QV etc. etc.) We were also told to apply the ointment, cover with dermeze and then do wet dressings. They made a huge difference to my DD's skin. If you google Royal Childrens Hospital Wet Dressings it will give you the instructions on how to do them.
Good luck, I hope you find what works for you. I spent a fortune on every miracle cure I could get my hands on and it turned out that a cream and the wet dressings and dietary changes were the "magic cure" for my DD.