I was a sinus sufferer for more than 10 years. I found last year i was very low on vitamin d. You can check your levels by the the 25 hydroxy test for the blood levels its not part of your regular blood test. I was very low. I read an article by Dr. Mercola, I got convinced vitamin d was my cure. I had to dose high on vitamin d3 and it cleared my sinus and post nasal drip. I have been clear for a month now but I'm convinced this is the cure for my condition. I suggest you check your vitamin d levels. If you are dark skinned you need to get lots of sunlight, living in the Northeast I don't have a choice but supplement. Dr prescribed me 50000 d2 but that didn't do a thing. If I hadn't read the article I would have never known the power of sunlight. This is clearing my longstanding dry skin as well.
I had all kinds of tests with all sorts of doctors and even corrected my deviated septum. The surgery created sinus issues for me.
The over the counter inexpensive vitamin d3 solved my sinus issues. Hope this helps good luck with your search.