I know that many of us have other disorders and syndromes as well. I've had IC for at least 6 years (undiagnosed for the first 2), then came CFS, and now apparently FM.
With IC - it is very easy (in my case at least) for someone to tell when I am in "trouble". I can literally double over immediately if a flare hits (and they ALWAYS hit suddenly), sometimes I can barely walk, you can always read the pain in my face. Needless, to say when I have an IC attack, noone tries to tell me "you'll be ok, you can stay a little longer, if you would just drink a beer you would feel better, etc. etc. It is absolutely accepted that I must leave NOW.
My daughter has IC also (unfortunately) and her flares hit her the same way. Her boyfriend knows when she is curled up on the couch, with the heating pad pressed so hard against her stomach you would swear it was going to burn her - that they will not be going anywhere that evening (or day).
Now by no means am I saying that people that have IC - "have it better". Trust me, I would not wish the PAIN that comes with it (and trust me, there have been times I have seriously considered ripping my bladder out). Also, nothing beats having to run to the bathroom every 10 minutes either.
Now, BEFORE I was diagnosed, I met alot of stupid doctors that told me it was basically "in my head". However, my husband, family and friends all knew there was something REALLY wrong with me and my husband went to at least 20 appts. with me over those two years.
Then comes CFS........from the beginning, I have been met with skeptiscm (sp? LOL), from some family, all my friends, and my husband. Even after being diagnosed. You can not normally tell when I am suffering, unless I'm passed out cold - at which point it's just assumed I'm "tired" and need to rest. There is no empathy, no understanding, and constant comments like "of course, you can go to the cook-out - you have to eat anyway" or "leaving already? you've turned into such a party pooper" etc. Because they can't SEE it. It is rare that my husband even recognizes when I am about to literally fall out. He even laughed off my neuro symptoms yesterday when I was telling him what was going on and said I was blowing them out of proportion - after all, he says - he can't spell either. (OK, big difference between never being able to spell and suddenly being unable to spell - but regardless.)
Then comes FM...........this one may be even harder. Everyone's pain is more than yours, everyone has "neck" or "shoulder" or throw in whatever body area pain and they just "get through". The pain is annoying, can be bad, but because of my IC pain, I must be covering it up better at times (you all know the pretend I'm fine face.....) Regardless, absolutely no support at all. In fact, we (the friend group) used to hang around someone with FM and they would constantly make fun of her behind her back............needless to say I have not even told any "friends" about this diagnosis.
So yes, technically they are all "hidden" illnesses. They all cause pain (different kinds, but it's still PAIN), they all cause sleep deprivation, they all create difficulties in your life. But in my experience - CFS and FM have been my turning point of being put into a different place in people's minds.........and I wish there was a way to change that.