CT scan is enough but an extra worry of Biphasic Anaphylaxis

Last time I had a CT scan I had a mild reaction to the contrast dye, and was given an IV of Benydryl and kept for observation. My symptoms were itching with a mild rash. Not a big deal.
However, the NEXT day in the late afternoon I had a huge reaction---my throat/tongue swelled up, BP plummeted and I became cold and clammy. Next thing I knew the EMTs were clumsily (yet fortunately, rapidly) sticking an IV in my arm, putting a mask over my face and carrying me to an ambulance.
It was very scary and confusing.
The ER Dr. deduced it was from the food I had eaten for dinner; some green curry from a local Thai place, and that was that.
However, yesterday I had the good fortune to see an intelligent allergist. He was setting me up for a protocol before my upcoming scan on Wed. to avoid the hives and itching, when I casually mentioned to him my experience with the green curry and how odd it was.
Turns out the food reaction was not a reaction to the curry at all (something I eat all the time) but a reaction to the contrast dye THE DAY BEFORE.
Biphasic Anaphylaxis is just like it sounds--a second-stage delayed serious reaction, in my case, to the contrast dye.
I need the CT scan but this time around I will be loaded up on steroids and benedryl, and kept for observation.
Feel immensely grateful for crossing paths with the Dr., as he just very well may have prevented another emergency, or tragedy.
Will post Thursday to tell you all it went well.
TommyCat