What is the chance of me having anaphylaxis to fludrocortisone? Is it higher than say Zantac (ranitidine) and other drugs or same? This terrifys me with any drug.

HIghly unlikely. I don't believe that this has been reported although anaphylaxis to solumedrol (methylprednisolone) (another form of cortisone) has been reported but the link is to the succinate ingredient and not to the cortisone molecule itself. Most of the cortisone allergy is related to contact dermatitis and not anaphylaxis. Your anxiety on this may be the cause for some of your reactions. Talk to an allergist.