Silver: Wow -- sounds like a heck of a reaction to something!
I wonder, too, about just plain drying of the sinus tissues -- that cold dry air dries everything out and makes you much more sensitive to things that may not otherwise bother you.

I agree with trying something like Claritin. You might also consider (and I hate using these so to recommend it is painful) a nasal spray that is just plain saline or something mild (ie, no "medicine" in it... that would only make things worse in the long run) -- use it prior to riding?

Just a thought. Good luck. Hope the ribs are better soon!
Jes