Contrast induced allergic reaction


  • Approximately 75 million doses of iodinated contrast agents are given worldwide each year
  • Many patients will report allergies to shellfish, iodine, or prior contrast infusions
  • Prior allergic or anaphylactic reaction to contrast infusion (whether low osmolality or high osmolality) is a contraindication to future contrast administration

Risk Factors

Clinical Features

Differential Diagnosis

Acute allergic reaction

Contrast induced complications


  • Clinical diagnosis


Acute treatment


  • Patients often report various allergies and there is controversy over the best way to prevent possible contrast induced allergic reaction

Shellfish Allergy

  • This allergy is specific to shellfish and does not cross react due to the Iodine rich nature of fish and the fish's tropomyosins and parvalbumin[1]
  • No pretreatment is necessary for shellfish allergies


  • There is no Iodine allergies which are compatible with life due to the existence of iodine in human thyroid tissue and distribution throughout the body

Prior Contrast Allergies

  • Pretreatment should not be attempted in these patients since there is a strong association between a prior contrast reaction and future anaphylactic contrast reactions[2]

Pretreatment with Steroids

  • There has been no difference found between ionic agents alone versus ionic agents with steroids in preventing allergic reactions. Non ionic (low osmolality) contrast agents are the preferred agent and do reduce the risk of allergic reactions. [3][2]


  • Any contrast reaction that is mild such as pruritus or mild urticaria can be observed in the emergency room for recurrent reactions
  • Severe anaphylactic reactions requiring multiple administrations of epinephrine should be admitted.
  • Patients receiving a single dose of epinephrine should have clinical judgment applied as to observation or discharge
  • All patients should be prescribed an Epinephrine Auto Injector regardless of disposition

See Also

External Links


  1. Schabelman E, Witting M. The relationship of radiocontrast, iodine, and seafood allergies: a medical myth exposed. J Emerg Med. 2010 Nov;39(5):701-7.
  2. 2.0 2.1 Lasser EC et al. Pretreatment with corticosteroids to pre- vent adverse reactions to nonionic contrast media. AJR AM J Roentgenol. 1994 Mar;162(3):523-6.
  3. Wolf GL et al. Comparison of the rates of adverse drug re- actions. Ionic contrast agents, ionic agents combined with steroids, and nonionic agents. Invest Radiol. 1991 May; 26(5):404-10