story:
i drove to an interview a couple of months ago and when i was getting into my car that morning, a piece of salt or sand or something blew into my eye. i probably had a slight corneal abrasion because my eye was bothering me all morning; i couldn't stop rubbing it.
i walked into my first interview and as i sat down, i said to my interviewer, "i want to apologize in advance - something blew in my eye this morning and it's been bothering me ever since." my interview said, "wow. wow! i'm really glad you said something to me, or else i might have just thought that you were really weird or nervous or something." (not verbatim, but you get the point). i was a little surprised by his reaction, but he then went on to tell me about a girl he interviewed who was a perfectly fine applicant, but who wore a nose ring. for some reason, the nose ring really bothered him, and he wanted my opinion about it. i personally didn't think it sounded like a big deal, but i said "yeah, i'm not sure why she chose to wear it... i guess it didn't occur to her that it was unprofessional."
so the moral of the story, like others have mentioned, is that you could run across some extremely conservative interviewers. better to hedge your bets and not wear an earring. once you get in to med school, get all tatted up and blinged out 🙂