Been using it from a nose spray bottle and it seems to be pretty effective in keeping the seasonal allergies from turning into a full blown sinus infection. Anecdotally, of course.The Betadine up the nose was mentioned in Joe Rogan's podcast where he interviewed a doctor for about 3 hours. I read part of the transcript and the doc did say to take it, watered down, up the nose all the way to the throat, then gargle with the remainder. He also recommended using mouthwash to get the taste out.
Here's a link to what I read:
Crib Notes From the Joe Rogan–Dr. McCullough Interview Everyone Is Talking About
Comedian Joe Rogan's December interview with Dr. Peter A. McCullough is fascinating. YouTube deleted the video, but here are some highlights.pjmedia.com