I like Texan's T-shirt idea:
"CROHN'S: Just because I look okay doesn't mean I am". I'd buy a tee like that! Of course, then I'd be announcing to everyone around me that I have Crohn's which I haven't done in my office yet...but still! Maybe one day when I AM ready for everyone to know about
my health issues, I'd wear that t-shirt to work. I'd definitely put that saying on my Facebook as a piece of flair.