In the stage where we didn’t know much about COVID early on, I experimented with a nasal lavage using Betadine, just to see if I could use it if needed. (around mid-March 2020, IIRC)
You squirt it up both nostrils with a refillable nasal sprayer, let it drain back into your throat, and then spit it out. Tastes and smells a bit nasty, but this kind of thing is done and is safe...as long as you dilute it enough!
I could do it, but right around that time, we learned more about COVID, and I deduced it wasn’t worth the hassle.
I figure if a really bad one comes out of Communist China (or our own country) that really WILL kill us, it might be worth trying.
My Wife has big bottles of Betadine at the barn. She uses it on her horses. I guess the medicine we use on the horses is good to combat covid. Ivermectin and betadine.
I’ve used Betadine gargle and nasal spray. You can make your own from cheap Povidone Iodine from the local pharmacy diluted 90% (or is it 99%? better check that).