Most people lack the medical literacy to understand any of this. People don’t read their letters telling them to not eat before surgery, are they going to read the list of potential side effects of a medication? How many people read the information sheets that come with their prescription medication?
But there’s a potential risk of an allergic reaction to any drug you take, any food or drink you consume, even environmental substances - perfumes; hayfever is an allergic reaction to pollens. You don’t know you have one until you have the reaction. I didn’t know I was allergic to penicillins until I needed them for an infection and it turns out I am.
There’s really a risk vs benefit. If you have a brain tumour you need contrast to assess the type of tumour, its growth, if it’s a glioma whether it’s transformed and so on. If someone is being given contrast it is going to change their clinical management.
It seems an odd fixation of just MR contrast when the same could be said of all drugs. Does your doctor/surgeon go into the minutiae of all drugs and possible consequences? By this line of thinking, saline is not without risks, should they go into depth about that?
People already poorly retain information or even comprehend it at appointments or interventions, is there any point adding more burden onto their attendances?