I'm allergic to the sort of adhesive tape they use to attach IVs and such. They always use it anyway and I end up with annoying wounds because of it.

Also, while not technically an allergy, if I were to be administered succinylcholine, it would cause malignant hyperthermia, rhabdomyolysis, acidosis, and cardiac arrest due to a genetic disorder. Luckily I didn't have to find out the hard way.