There's an old topic here on AP about Stilton and penicilin that may give you some hints: Stilton and Penicillin. There is an interesting article on WebMD which says that many people who think they are allergic to penicillin are in fact not, and also lists other anti-biotics you may be allergic to: WebMC article on penicillin allergy.
It would probably be a good idea to get tested, as if it is penicillin or a similar allergy, it could have serious consequences.
