body imaging
"Had a precautionary CT scan on my chest several days after hip surgery and after experiencing some pain in my  chest. The contrast agent used was Omnipaque 350. About 8 hours later when lying down in bed I felt itching on my back which persisted into the night. On inspection I could see that a hives type rash had formed between my shoulder blades. This gradually subsided over about 10 days.

Note that the scan showed up a small infection for which I was prescribed a penicillin antibiotic. I took this about 3 hours before the rash appeared so my doctor changed the antibiotic as a precaution in case that caused the rash. I have never been allergic to penicillin  so in my mind the Omnipaque remains the culprit"