I see this all the time. I can't have that antibiotic because I'm allergic. I'm allergic to tylenol but I can have percocet (tylenol/oxycodone). I spend so much time educating people about their "allergies". As an EpiPen carrying victim of the hypersensitivities, I cannot tell you how frustrating it is when it impedes care.
Zdogg interviews a board-certified allergist to answer your questions which are not only well informed but entertaining. Please have a listen. Warning there is one area not suitable for children regarding a bodily fluid allergy.
Thank you Zdogg MD