What Causes Rash On Right Arm And Itching Between Fingers?

Hi, I am a 27 year old female who recently had an allergic reaction to hydrocodone which was given to me for pain. After receiving a shot in the emergency room the doctor prescribed me prednisone. I took the prednisone and I had an allergic reaction to that so I stop taking the dose pack. Every since(for a month), I have been breaking out in a red rash on my right arm all the way to my fingers. I have a severe itch between my fingers and on the inside of the palms of my hands, on my neck, and face(especially my eyes). This all also happens when I go outside in the sun or when I get too hot or if I eat or drink anything. I am concerned because I don't know what is causing the reaction. I am very concerned about going into anaphylactic shock because I don't know what triggering these reactions. Help me please!