“If I have a shellfish allergy can I have iodine contrast?”
I've heard that iodine is used in some CTs. I have a shellfish allergy. How does that work?
10 Answers
Yes. You can be pre treated with medications to greatly decrease your chance of an allergic reaction
Two different immune globulins are at work here. Your eating side has IgE immune globulin. Your blood side is IgG. Thus, shellfish allergy shouldn’t affect you receiving IV contrast. You might want to use oral barium contrast if ingested for a GI CT study.
Yes, that is an old incorrect assumption. Studies have shown there is no cross reacitivity
Yes. It use to be thought that there was a correlation with shell fish allergy and iodinated contrast, but this has been debunked.
Dr Cox
Dr Cox
It's basically an urban legend that'll never die. All it means is that you're at slight increased risk to have a non-specific allergic reaction. There is no cause-effect or cross-reactivity.
Below, is an excerpt from the American College of Radiology contrast manual:
Allergic-like reactions to modern iodinated and gadolinium-based contrast medium are uncommon (iodinated: 0.6% aggregate [1], 0.04% severe [2]; gadolinium-based: 0.01-0.22% aggregate [3], 0.008% severe) [3,4]. Risk factors exist that increase the risk of a contrast reaction. These generally increase the likelihood of a reaction by less than one order of magnitude, effectively increasing the risk that an uncommon event will occur, but not guaranteeing a reaction will take place. The following are some examples: Allergy: Patients who have had a prior allergic-like reaction or unknown-type reaction (i.e., a reaction of unknown manifestation) to contrast medium have an approximately 5-fold increased risk of developing a future allergic-like reaction if exposed to the same class of contrast medium again [3]. A prior allergic-like or unknown type reaction to the same class of contrast medium is considered the greatest risk factor for predicting future adverse events. In general, patients with unrelated allergies are at a 2- to 3-fold increased risk of an allergic-like contrast reaction, but due to the modest increased risk, restricting contrast medium use or premedicating solely on the basis of unrelated allergies is not recommended. Patients with shellfish or povidone-iodine (e.g., Betadine®) allergies are at no greater risk from iodinated contrast medium than are patients with other allergies (i.e., neither is a significant risk factor) [5,6]. There is no cross-reactivity between different classes of contrast medium. For example, a prior reaction to gadolinium-based contrast medium does not predict a future reaction to iodinated contrast medium, or vice versa, more than any other unrelated allergy.
Bottom line, get your CT scan and we won't serve you shellfish ;-)
All the best.
Below, is an excerpt from the American College of Radiology contrast manual:
Allergic-like reactions to modern iodinated and gadolinium-based contrast medium are uncommon (iodinated: 0.6% aggregate [1], 0.04% severe [2]; gadolinium-based: 0.01-0.22% aggregate [3], 0.008% severe) [3,4]. Risk factors exist that increase the risk of a contrast reaction. These generally increase the likelihood of a reaction by less than one order of magnitude, effectively increasing the risk that an uncommon event will occur, but not guaranteeing a reaction will take place. The following are some examples: Allergy: Patients who have had a prior allergic-like reaction or unknown-type reaction (i.e., a reaction of unknown manifestation) to contrast medium have an approximately 5-fold increased risk of developing a future allergic-like reaction if exposed to the same class of contrast medium again [3]. A prior allergic-like or unknown type reaction to the same class of contrast medium is considered the greatest risk factor for predicting future adverse events. In general, patients with unrelated allergies are at a 2- to 3-fold increased risk of an allergic-like contrast reaction, but due to the modest increased risk, restricting contrast medium use or premedicating solely on the basis of unrelated allergies is not recommended. Patients with shellfish or povidone-iodine (e.g., Betadine®) allergies are at no greater risk from iodinated contrast medium than are patients with other allergies (i.e., neither is a significant risk factor) [5,6]. There is no cross-reactivity between different classes of contrast medium. For example, a prior reaction to gadolinium-based contrast medium does not predict a future reaction to iodinated contrast medium, or vice versa, more than any other unrelated allergy.
Bottom line, get your CT scan and we won't serve you shellfish ;-)
All the best.
You possibly need to be pre-medicated by steroids ot benadryl, if you have CT with contrast material
Yes. Your body needs iodine and uses it every day. There is iodine in both she'll fish and CT contrast but that is not the antigenic agent. It is something else. While it used to be thought the allergy to shellfish precluded the use of iodinated contrast, that is no longer the case. If you are concerned you can premedicate with an antihistamine like Benedryl and ask your primary care physician for a prescription of steroids to take thirteen hours and one hour before iodinated/CT contrast administration. ALWAYS drink 4-8 glasses of water before and after the contrast in order to protect and flush your kidneys.
Unless there is some highly specific reason, we don't need to use all this contrast material in our imaging studies, I recommend you avoid it, dlh
As a general role, shellfish allergy does not have any relationship to iodinated contrast. If you are concerned, you can take 50 mg of Benadryl before the study.
Yes
