Contrast Dye – Side Effects and What You Should Know

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Contrast Dye and What You Should Know About It


What is a Contrast Dye?  

In medical science, contrast dye plays an essential role in solving human health riddles. Using different types of tests like CT scans, MRIs and angiograms, doctors and ancillary healthcare workers can begin to unravel mysteries of the human body. Although not the only piece of the puzzle, these scans provide a significant advantage when it comes to knowledge and detection of many ailments. For this purpose, a liquid solution called contrast dye is used.  

When looking at structures inside of the human body, the contrast agents help accentuate and focus on specific areas. How they work is simple: the chemical composition of the contrast dye allows it to be seen distinctly on the imaging scans. Contrast dye itself shows up as a bright white color, making it easy to differentiate from other tissues and structures.   

In magnetic resonance imaging or MRI scans, contrast dye works as an altering agent. It increases or decreases the relaxing time of the nuclei in the body tissues. This, in turn, alters the contrast of the image.  Contrast can function to outline the walls of a structure, like blood vessels. It can also show when an increased flow of blood is going to a certain place in the body. Or perhaps it is showing there is blood somewhere that it shouldn’t be at all. 

Types of Contrast Media 

Radiology Contrast Agents are the most commonly known types of contrast. There are two main types of contrast used in imaging modalities like X Ray, CT, and MRI studies:

  • Iodine-based contrast dye which is injected using intravenous catheters (commonly called “IVs”).
  • And non-iodine contrast like barium-sulfate, used for oral or rectal applications.

Iodine Contrast medium (Intravascular):  

This is a type of intravenous contrast dye (a radiocontrast agent). As is termed, it contains Iodine. This is useful in enhancing the visibility of vascular systems and organs. When iodinated contrast is applied, some pathology like cancer displays better visibility.  

Iodine contrast is classified into two major types called ionic and non-ionic. They are both relatively harmless and don’t usually have side effects. Because of this factor, it is most commonly used in radiology. They are also known to be well soluble. On occasion, some patients have a reaction so speak to your physician before use. 

Gadolinium contrast agents are a form of contrast dye and are used in MRI scans. They are injected into a body, which works to improve the diagnostic quality of the images. They are known to produce much better results in detecting tumors, inflammation, nerves and blood vessels and blood supply around the body.  

Contrast Dye: Side Effects and Alternatives 

There is nothing absolute in medicine, and to each person, there can be a different adverse effect. While relatively safe in the majority, there are adverse contrast dye side effects. In most reports, the side effects include contrast dye allergy reactions, hyperthyroidism, and contrast-induced nephropathy accumulation of metformin.  

In earlier forms of Iodine contrast, people with Myasthenia gravis faced an increased chance of exacerbation of the disease.  

Additionally, there is also a hypersensitivity reaction. Some allergic reactions can cause severe anaphylaxis, but this happens rarely. This can occur after injections, or after rectal or oral contrast. This can also be produced during pyelography treatments. 

In order to avoid these problems, there is contrast dye allergy premedicationDepending on the physical condition and health, the radiologist will suggest premedication protocols. Commonly, the intake of drugs like oral antibiotic agents is stopped forty-eight hours prior.  

Is there an alternative to iodine contrast Dye? 

contrast-dye-know-your-optionsObviously, people facing these problems might look for a replacement. There are some alternatives to iodine contrast dye, but among the preferred ones are non-ionic in chemical composition. As a result of the allergies, some people are unable to go through the treatments and tests necessary. According to studies, patients with allergies to iodine contrast dye displayed mild to moderate reactions. At this level, they are not life-threatening. Gadolinium contrast also uses a smaller amount, not exceeding 40 ml. It works as a better alternative during the evaluation of coronary artery diseases. 

Besides a history of a previous allergic reaction to contrast, it is also advisable to consult your physician prior to use if there are open wounds near the area requiring examination, and during and nearing pregnancy. Other factors like alcohol in the system, asthma or drugs need to be shared in the patient’s history with the Doctor for compatibility.  

Late Side Effects:  

Some side effects tend to emerge only late after the treatment or test has been carried out. It can happen anywhere after 15 minutes to one week, once the procedure is completed. Contrast dye allergy symptoms might include warm feeling around the throat area. The feeling moves toward the pelvic region after a while.  It can mimic the need to urinate as if to have a full bladder. 

The feeling and urge to vomit and mild nausea might also take place, but this occurs mostly in only 5-8% of the patient. These are the minor symptoms that resolve themselves after a while and do not necessitate treatment. 

Observed in 1% of patients are symptoms that require contrast allergy treatments. The symptoms may include vomiting, swelling, and hives. Benedryl and anti-nausea medications are commonly given for these symptoms. While not very severe, they pose a mild/moderate threat and should be evaluated by medical personnel if persistent for long. 

And then there are the life-threatening symptoms observed in less than 1% of patients. The symptoms might include anaphylaxis which leads to difficulty breathing. The healthcare team is trained to respond to all of the symptoms we have mentioned. 

Other symptoms like arm pain after IV contrast are natural and wear off after a minimum time of thirty minutes.  

Iodine concentration affects the severity of the allergies. As such, patients would feel fatigued after a CT scan with contrast, mild irritation all over the body, all depending on the medium used. 

Can contrast dye make you itch? 

The following reactions are observed in the corresponding practices:  

Contrast side effect after an X Ray exam: 

  •  Vomiting and nausea 
  • Abdominal cramps 
  • Diarrhea 
  • Constipation

Iodine contrast side effect after CT scan 

  • Hives and Skin rashes 
  • Headache 
  • Itching 

If the patient suffers from symptoms like trouble in breathing, swelling and high heart rate after an exam with contrast, immediate medical attention should be sought.  

Mythical Allergies De-bunked: 

There is a common belief that patients who have shellfish allergy cannot have contrast dye when they need CT scans performed. This belief arises from “iodine allergies” because shellfish contain Iodine.

Contrast-Dye-Does-Shellfish-MatterIs Shellfish allergy contraindication to IV contrast?

The answer is no.  

Most physicians will say iodine allergies simply do not exist. Iodine is present in our bodies and is also present in most salt used around the world.  

However, a person can have an allergy to shellfish, and the iodine present in said shellfish is not the cause. In most cases, it is the proteins called Parvalbumin and tropomyosin acting as allergens. Thus, Shellfish allergies do not contribute to iodine contrast side effects. 

Shellfish allergies and betadine are not in any way contributing to risks of getting contrast treatment. However, betadine may cause rashes in people with sensitive skin; it does not mean a person is allergic to Iodine. In any case, it should be safe to conduct contrast dye allergy treatment.

What is the medication for contrast Dye allergy? 

Most of the allergies and side effects occur by twenty minutes after the administering of the injections. This could require a post administered treatment. 

For the contrast allergy pretreatment, it is crucial to understand that preparation is very important. Prednisone and Benadryl for hives and other symptoms will be prescribed by the healthcare providers most of the time.  

Before administering the contrast dye injections, the standard intake for the contrast allergy prep could be prescribed in general as follows: 

  1. Twenty four hours before the procedure, you must administer 50 mg of Prednisone orally. 
  2. Twelve hours the procedure, you must administer another 50 mg of Prednisone orally. 
  3. Finally, one hour before the procedure, both Prednisone and Benadryl must be administered orally. 

This is not the only premedication treatment available and only your physician can prescribe what is right for you.   The important thing is to minimalize the risk of extreme allergic reactions.

In MRI, a procedure known as an Arthrogram uses a contrast dye. This is a fluoroscopy procedure and helps to see specific places in the body. As far as the fluoroscopic injection side effects go, infections, bleeding, headaches, and nerve damages are the possible side effects. 

Mood swings and insomnia are some more rare cases that last for seven to ten hours after the procedure.  

Patients suffering from chronic health conditions should consult physicians for an assessment to sort out any kind of risk. 


Treatments are not cheap, especially in the private sector. Before participating in any sort of imaging studies, it is essential to know what one is signing up for. It is best to prepare, and be well informed in medical science. Whether going for an MRI, CT scan or general X Ray, contrast dyes can have adverse effects depending on the individual. Thankfully, there are ways to prepare before the treatments and tests commence.  Plus, medical staff is trained routinely on how to react after a study if you should have a problem.

Contrast materials, however, are safe in the majority of cases. Of course, there are side effects and symptoms, but those are uncommon and occur in a few rare cases. And if the patients present with those problems, the department of Radiology has the equipment and medications necessary to take care of them. 

But any allergies to drugs, food, animals, preservatives and contrast materials should be confided with the experts. It is also essential to make sure any medications the patient is on should be told to the doctors, including supplements and herbal medicines.  

Other factors, like new medical conditions, illnesses, as well as surgeries, should be discussed. It is also essential to come forth with any health factors like Asthma, Kidney diseases, heart diseases, and thyroid problems. 

This material does not constitute medical advice. It is intended for informational purposes only. No one associated with The Radiologic Technologist will answer medical questions via e-mail. Please consult a physician for specific treatment recommendations.

For further information please consult the ACR Manual on Contrast Media and its references. You may find it here on the ACR website.


Blackwell, R. H., Kirshenbaum, E. J., Zapf, M. A., Kothari, A. N., Kuo, P. C., Flanigan, R. C., & Gupta, G. N. (2017). Incidence of adverse contrast reaction following nonintravenous urinary tract imaging. European urology focus3(1), 89-93.

Contrast Dye and the Kidneys. (2017, March 24). Retrieved October 13, 2019, from

Horowitz, J. M., Bisla, J. K., & Yaghmai, V. (2016). Premedication of pregnant patients with history of iodinated contrast allergy. Abdominal Radiology41(12), 2424-2428.




Ron Jones MSRS, RT (R,CT) ARRT

Ron is huge radiology nerd. It started with Xray school at Pima Medical Institute in Mesa, AZ. He was crosstrained in CT during his Xray clinical rotations at Mesa General Hospital. Then immediately returned to school for ultrasound at Gateway Community College as he started his first job as an Xray/CT Tech. Not much later learned MRI out of necessity at his small rural hospital in Apache Junction, AZ. A decade later he found himself as a manager in a level one trauma center. Currently he is a system operations director over an entire hospital system and loves every minute of it.

One thought on “Contrast Dye – Side Effects and What You Should Know

  1. When a patient says they have a shellfish/iodine allergy, it is nothing to take lightly. My Mother “coded” on the Xray table after being injected with imaging dye. She had repeatedly told the doctors that she had those allergies and she had been injected before and didn’t like the way it made her feel. But, it took her nearly passing away before anyone would really listen to her. After that, no more imaging dyes and, since I share the same allergies, I always make a point of telling this story to get my point across.

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