Okay guys, you know who you are, listen up.
If this doesn't apply to you, point it to somebody to whom it does. I've found the world's simplest sinus headache cure. Much more effective than other methods to which I've been reduced, like sticking my nose in the vacuum cleaner, because OTC painkillers aren't even slowing the pain down. (Don't laugh. Okay, go ahead and laugh, but I get them bad.)
It's a variant on something my Dad used to use for migraines.
The loose theory is that sinusitis involves the swelling (obviously) and irritation of the sinuses. So the first key to reducing sinus headache isn't to pop pills, but to simply reduce the irritation.
How do you do that? Cut out the dryness from the equation. If you work in AC, the dryness of the air is one of the issues with which you're having to deal. But since running humidifiers all the time isn't much of an option, especially in the summer time, or in places where mold is a serious issue....
Step One: do you have a sinus headache? Is ragweed kicking your butt?
If yes, proceed to step two.
Step Two: get a paper towel or washcloth. Wet that sucker down with the hottest water you can get. If you're at work in an office, that's probably the hot water on the side of the coffee machine that some NPR listener is using to brew green tea at 8 a.m. while the rest of us are drowning in our coffee pools. At worst case, you may be forced to boil water. Go for it.
Step Three: Put this ridiculously hot cloth right on your nose. Yes, I know, it's hot. Deal with it, you have to be in contact with the cloth for this to work.
Step Four: Inhale through the wet washcloth or paper towel. It should be close enough to your nostrils that you can literally hear the water burbling the fiber matrix as your inhalation strips it from the progressively-cooler towel.
Instant portable humidifier. It won't last you all day, but I've found that I get a pretty consistent fifteen or twenty minutes of being able to breathe beautifully with no sinus pain at all, followed up with the pain camping out at a much more tolerable level for the next couple of hours. Which means that if you have a hot tap and can do this in a convenient fashion, it's no sweat to "huff fabric" six or seven times a day.
And that's a heck of a lot better than suffering through the alternative.