TOPLINE:

The administration of iodinated contrast media (ICM) between January 2014 and November 2024 in the US resulted in anaphylaxis at a rate of 20.3 cases per 100,000 scans, 13% of which were life‑threatening. Only half of patients received epinephrine, with higher administration rates in emergency departments than in inpatient and outpatient settings.

METHODOLOGY:

• Researchers sought to determine the frequency of anaphylactic reactions to ICM and to categorize the reactions as monophasic, biphasic, refractory, or life-threatening.
• They assessed 702,917 CT scans involving ICM and included 143 patients (median age, 54 years; 64% women; 87% White) who had developed anaphylaxis.
• Monophasic reactions were single‑phase events, whereas biphasic anaphylaxis was defined as the recurrence of hypersensitivity symptoms within 48 hours of the initial reaction after an asymptomatic interval of at least 1 hour, without reexposure to the allergen.
• Refractory anaphylaxis was defined as a reaction that required three or more doses of epinephrine or the initiation of an intravenous epinephrine infusion with symptom‑directed care. Life‑threatening reactions included any severe cardiovascular, respiratory, or neurologic manifestations.

TAKEAWAY:

• Overall, the incidence rate of ICM-induced anaphylaxis was 20.3 cases per 100,000 scans (95% CI, 17.2-24.0) and 47.9 cases per 100,000 patients (95% CI, 40.5-56.6).
• Of 143 anaphylactic reactions, 97% (95% CI, 92%-99%) were nonfatal monophasic, 3% (95% CI, 1%-7%) were biphasic, 10% (95% CI, 6%-16%) were refractory, and 13% (95% CI, 8%-20%) were life‑threatening, including one fatality.
• The incidence rate of life-threatening anaphylaxis was 2.7 cases per 100,000 scans (95% CI, 1.7-3.9), with a fatality rate of 0.14 cases per 100,000 scans (95% CI, 0.07-0.87).
• Antihistamines were given in 76% of cases, corticosteroids in 55%, and epinephrine in 50%; emergency department cases were significantly more likely than outpatient and inpatient cases to receive epinephrine (risk ratio, 1.84; P < .001).

IN PRACTICE:

“Our findings underscore the unpredictable nature and potential severity of subsequent reactions to contrast, even among patients who receive premedication, and highlight the importance of careful risk assessment and adherence to evidence-based preventive strategies,” the authors wrote.

SOURCE:

Eduardo Saadi Neto, MD, with Mayo Clinic, Rochester, Minnesota, was the corresponding author of the study, which was published online on November 16, 2025, in Annals of Allergy, Asthma & Immunology.

LIMITATIONS:

The study’s single-center and retrospective design; low frequency of biphasic, refractory, and life-threatening reactions; subjective diagnostic classification; and lack of consistent postdischarge follow-up may have affected the outcomes.

DISCLOSURES:

Some authors reported receiving investigator-initiated research grants and royalties, serving as consultants and scientific advisors, and holding positions with various pharmaceutical companies and institutions. One author reporting owning stock in AbbVie.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.