Both my father and I have gone to doctors, and were diagnosed with inflammation. That was a long time ago and I don’t remember the specifics, but essentially, it’s the kind of disease that is chronic and they didn’t really know the specific cause of it. We got prescribed those steroid nose spray to use on a bad day. It helps to an extent, but not quite solving the problem. The effect only lasts for a few hours and I think they strongly recommend against using it more than once a day. Plus it’s kinda expensive if used frequently.

Drinking a lot of water, on the other hand, has a huge effect on my breathing. I can breath through my nose all day now. It probably doesn’t treat the underlying cause, but symptom-wise, it works better than any prescription I’ve taken.

I’m in no position to give real medical advice, but since drinking a bit more water is usually regarded as harmless (2.5 liters is well within the safe range of water intake as far as I know), I’d say give it a try. Just prepare to pee more frequently.