We see a LOT fewer reactions to contrast than we used to, since the development of non-ionic, iso-osmolar contrast agents (Omnipaque, Visipaque, for example).
They still contain iodine.
Which makes one wonder just what is the reactive ingredient??
Bottom line: be prepared at any time for a reaction to ANYTHING (antibiotics, prescription or OTC meds, bee stings, etc), even if one has not previously had a reaction.
Sensitivity can develop AT ANY TIME, and WITHOUT WARNING.
(I always carry Benadryl)
(off-topic but pertinent:
I had a severe allergic response to a bee sting while we were out camping with friends.
Had NEVER had problems with stings before.
It developed and progressed quickly.
Luckly dh had Benadryl with him and I took two.
Being the nurse that I am, I did not call 911, but monitored myself [yeah, I know; but you know how we are!!!] for an hour.
Airway wasn't compromised but there was significant swelling of the neck [I looked like Jabba the Hut, when I finally got to a mirror] and face.
I could tell airway was encroached upon but trusted the Benadryl to decrease the severity of the swelling.
Yes I now carry an Epi-pen.
And counsel all to carry Benadryl with them.
That is all, carry on!