The most serious contrast reactions are Allergic-type reactions Contrast nephropathy (renal damage after intravascular injection of a contrast agent) Allergic-type contrast reactions Reactions vary in severity: Mild (eg, cough, itching, nasal congestion) Moderate (eg, dyspnea, wheezing, slight changes in pulse or blood pressure) Severe (eg, respiratory distress, arrhythmias such as bradycardia, seizures, shock, cardiopulmonary arrest) The mechanism is anaphylactoid (see Anaphylaxis); risk factors include the following: A previous reaction to injected contrast agents Asthma Allergies Treatment begins by stopping contrast infusion.