For the record (in case anyone benefits by this) I decided to post about both mine and my father's experiences with sinus conditions.
MY CONDITION (hidden allergy to onions/garlic):
For years I'd been suffering bouts of terrible sore throat (it felt like swallowing knives and it hurt me to even whisper the M/N sounds). It would also would reach my sinuses - my nasal passages dripped like a gushing faucet. I'd also get headachy.
Then a few years ago I desperately chewed on raw garlic cloves in the hope of relieving my terrible condition. Instead, my condition got MUCH worse.
And that's when the light dawned. I realized that my condition was CAUSED by allergy to garlic & onions. (If they're well-sauteed & then well cooked, then they're OK).
It's been a long time since I suffered such a condition. I attribute this to a few things: (1) always blowing my nose immediately upon feeling my nose running - such as after drinking a hot drink or exposure to cold (2) keeping myself warm, staying under the blanket at night to breathe in warm air (3) avoiding onions/garlic, such as garlicky pickles, oniony herring or salads. Also making sure that soups contain well-sauteed onions which are then cooked for hours in the soup.
MY FATHER'S CONDITION:
For years, my father (a senior citizen) would, like me, have a tendency toward laryngitis, always clearing his throat and getting colds and sore throat.
When I realized that onions/garlic were my culprits, I warned him against these foods. Interestingly, for the past several months, he has been speaking regularly with no need to whisper - HOWEVER:
However, for the past 2 months, he has been complaing of a burning behind his eyes, and a "hollowness" up his nostrils. (I get this same reaction after taking zinc-based Cold-Eeze which dries me out).
Interestingly, when he was recently exposed to a prolonged blast of cold air from outside (which he's usually protected from) he was finally able to sleep through that night.
This would point to the fact that he may be allergic to dry heat. Maybe he requires prolonged cool-wetness? It's a mystery. Maybe he should try irrigation and Xlear?
So my father's situation is only a partially-solved mystery.