What Is The Treatment For Painful Red Welts?

The day before yesterday I broke out all over with large painful angry red welts. I have been suffering from eczema for l=the last few months, but this was completely unlike what I have been experiencing. I went to the ER and the doctor there prescribed me prednisone and benedryl. I was fine yesterday morning but later in the day the welts back back furiously and have noved to my legs as well. What should I do?