Move. Yes, that's the solution to most of it. Move west to a drier climate. My doc told me that 80-90 percent of folks living along the gulf coast or in the deep south have sinus problems. Humidity is not your friend. Move. OC drugs work a little but have side effects. The only other solution is stay inside with the A/C cranked. Of course since this is a MH traveling kinda site, another solution could be to head north during the hot humid months. Or west - Wyoming, Montana. Last but not least, the truth we all must face: Aging ain't for the faint of heart.
North in summer.
South in winter.
If you go to Denver you can smoke a lot of dope legally. Might not cure your allergies but you won't care.