I am having an allergic reaction 2 days after having a ct scan done. is this common and how should i treat it? itchy red whelps all over me.

Notify your doctor: Notify your doctor as soon as possible about your reaction. You likely have a reaction to the contrast agent used for the ct scan. Antihistamines may alleviate the itching. Some allergic reactions can progress and be quite severe. A life threatening condition called stevens-johnson syndrome can be a consequence of some drug allergies. Allergic reactions are relatively uncommon but may be serious.

Benedryl: Is a good place to start but if you're having shortness of breath, tongue swelling or difficulty swallowing please go to the er or call 911.

Contrast reaction: Make sure to let your doctors know you had this delayed reaction to intravenous contrast. Next time you are scheduled for a ct scan, angiogram, or any xray test requiring intravenous contrast, you should be premedicated with benedryl and Prednisone pills 24 hours prior to the contrast injection to lessen the risk of a more severe allergic reaction (i.e. Wheezing, throat swelling, anaphylaxis).