Same here. For years I've worn a stainless steel Medic Alert wrist bracelet with a largish medallion (about 1 1/2" X 1"). It's never set off the metal detector, and I would never think of taking it off, because owing to the odd clasp design it takes my wife and me, both, to get it back on. Never been a problem though.

I am glad you're thinking of wearing something from Medic Alert for your allergy -- it is an underused and potentially lifesaving resource.