I found a little information below:
...A lack of exercise results in a sluggish blood flow. Stagnant allergens gather in a fixed position, which begins to destroy the tissues around them. Constant movement of the allergens through the blood stream prevents these delicate tissues from becoming inflamed...1
...A stuffed nose is worse when lying down. Sinuses don’t have gravity working with them to drain cavities blocked by mucus...1
...Sinus congestion is also loosened by increased temperature in the body’s core...2
So what we have is that we need the blood to move faster, be upright and increase our bodies temperature. These are some interesting things to note.
Now I notice it says that the allergens "destroy" the tissues around them, I would love to know what "destroy" means in this context. If something is being destroyed, can it be rebuilt (in this context), also I guess my understanding of what allergens are is beginning to change.
Previously I had always heard that the "reaction" we see is histamine attacking the allergens (even though they're really not dangerous). So are allergens dangerous or are they not and the histamine is destroying tissue.
Again if you're a doctor/allergist/researcher, I would love your input.
Good luck.
1 http://fitnessandwellnessnews.com/exercise-control-of-your-allergies/
2 http://fitnessandwellnessnews.com/work-out-sinus-pressure/