As for myself, my nose runs like a river all the time. No allergies, according to multiple tests. Such is life.
Have you tried a neti pot?
I find the only thing that helps my allergies is living in a cold, dry climate with a short growing season. I'll start to suffer a bit sometime next month and it'll all be over by mid September.
I've thought about that, just haven't gathered the energy to go and get one. In the meantime, I just go for a run. It gets everything - really, everything - out!