I used to have sinusitis really bad, until I discovered that I had a root canal that was the cause of the problem. Here is an article I wrote some time ago about teeth, they can be a hidden health hazard: http://tinyurl.com/3lxwmde
AFS (allergic fungal sinusitis) is a BIG problem, you can read more about sinus issues here: http://tinyurl.com/c43xlrc