Morphine Sulfate SR and hives

I had a large LEEP procedure performed in the OR this past Thursday for treatment of pre cancer and possible cervical cancer. I received a spinal for the procedure and everything was going fine until I asked for pain meds about five minutes post op. They decided to give me morphine. I am allergic to quite a long list of medication, but did not think that this one would be added to my list. About 5 minutes after I received my morphine injection I started feeling funny and got really itchy. I asked the nurse to figure out why I was feeling so bad and she showed me a severe hive that was raised about an inch off of my body, and my blood pressure was dropping. An hour and a half later (after a Benadryl injection) I started feeling a little better and was taken to my regular room. A couple hours after I arrived there the hives started coming back and I was given another injection of Benadryl. My body is still trying to fight off the adverse reaction, and I was sent home on medication to help flush the morphhine out of my body. This stuff is horrible!