I had a non-sinus sinus infection for two years before I had a lactose
problem.
I was on various antibiotics which had no effect.
I  have been arthritic since my 20's and I was told that this was an
arthritic problem (ear pain and facial pain). A low dose of steroids clears
it up in two days.
I don't knowingly eat any dairy as my lactose interolence level is off the
charts and I still get the face pain thing at times so....for whatever its
worth...
Myra