Yes, ethandron, I know exactly what you mean, but I have no idea why. Unfortunately, as I discovered, I am also allergic to the contrast dye (I think it's iodine) and spent the week after the CT scan on steroids and antihistamine till the full body rash disappeared. Not a lot of fun, and also makes me wonder what else I might be allergic to (seaweed? - not that it's on my regular menu)