Head CT with dye?

Well after my 10 day long headache and trying a few meds, with Maxalt finally working a bit, I went back to my dr. for a follow up visit.  He ordered a CT scan of my Head and Sinuses.  The Head CT is going to be both with and without dye, and I've never had dye injected in me before.  I'm kind of nervous about it now.  The lady on the phone asked if I have ever had an allergic reaction to x-ray dye before, which makes me feel a little uneasy about it.  Do they inject it in an IV or what?  Thanks for any input or reassurance you can offer. 

I had it done back in January and it is pretty fast and easy. They inject you in an IV and it literaly takes like 15 seconds to inject it. It did not take long at all. It feels kind of cold throughout your body but no pain or discomfort really. It is really simple so you really have nothing to worry about. Good luck and hope that they don't find anything in the MRI!