Nose running all the time. I use Flonase allergy spray every day. Helps calm down the runny nose for me. On o2 24/7 as well. Nose is raw and bleeds easy. Unfortunately all this is part of this crap we have. Hang in there

Most complain that Oxygen use dries out the nasal passages, not the other way around.🤔
Anyway, the normal concentration of Oxygen is about 21% in room air. Nitrogen actually makes up 78% most of what we breathe. These numbers have nothing to do with the readings on the oximeter tool for checking blood saturation though.
Even with oxygen tanks or concentrator machines, it would take about 5 liters of steady flow to deliver "pure" oxygen in about a 40% range. Even in the hospital setting, Higher Flows of 10-15L would be required to bring a low oximeter reading into the mid-90s. Anything above a steady 96% on the finger-thingy would be difficult to maintain. Comfortable breathing is more Art than Science, for sure.

I do have two or three allergies. I was just thinking that it might be the fact that you're running pure oxygen into your nose which normally doesn't take 99.9% pure oxygen and the linings of your nose esophagus could become a little swollen feel a little parched at times having taken the moisture right off the lining of the deduct work from your nose. The oxygen machine does have a water humidifier on it and I didn't think that was a problem at all because I normally run 30 to 35% humidity in the house. Just a bunch of comparisons. Take care and enjoy the day.

My nose does not run at night. I do wake up with a dry nose and I use a moisturizer spray in the morning..
Hope you’re having a good day
Be safe stay positive

We're on the same page, Ken.
For another comparison, Deep Sea diving gas tanks have a mixture of about 32-36% oxygen, much less nitrogen and a bit if Helium to prevent getting "drunk" at extreme depths. Yes, that's the same helium that makes you sound like Donald Duck. That mix is called "EAN - Enriched Air Nitrox" and is about as Pure as it gets. Unless you are a fish.
Be well.