Skin reddens w/o pain when scratched (arms, stomach) after abdomen ct scan with contrast . caused by the iodine or radiation? lasted couple days.

Iodine reaction: Usually a rash after a scan with IV contrast is due to all allergic reaction to iodine.

Talk to your doctor: Most likely, you have a mild allergy to the contrast, which contains iodine. The radiation involved with a ct of the abdomen is minimal. Talk to your doctor, as you may need to be premedicated with two drugs the next time you will need a radiological test with contrast.