Question:
I am a 69 YO Male. About 25 years ago I was given a small test dose of IVP Dye. I got sick and vomited. The doctor told me that I was allergic to the dye and would not complete the test. Last year I a a CT scan with IVP Dye after taking a steroid and benadryl prep. This worked out ok. I am scheduled for another scan next week using the same prep protocol. My question is: just how safe is this?
Answer:
The dye used now for IVPs is different from the one used 25 years ago.
Both give me fierce headaches, but the new dye is said to be much safer
than the older one. You don't know that the two dyes are the same substance. After 25 years, it's doubtful that they're the same. Also, vomiting from a dye is not the same thing as being 'allergic'. I am on a personal crusade to define exactly what an 'allergy' is. Even if the dye might make you vomit, it may well be the correct thing to do to give it to you anyway. Contrast dye reactions can occur sometimes and not occur other
times even with the same material and the same prep. Others have
pointed out that it's not clear that vomiting represented an actual
dye allergy, but assuming it did, a person with a prior reaction
is at higher risk for future reactions to dye. It's generally felt
that with newer contrast materials plus the Benadryl and steroids,
the risk of a severe contrast reaction is pretty low, so that if
there's a good reason to get a study that requires contrast it's
a not a major contraindication. That said, the risk is not zero
even in someone who never had a contrast reaction, and there should
always be a good reason to get the test.
