Using a Q-tip, dip one end in body temp water and then into capful of hydrogen peroxide, you want a slight dilution of the peroxide, very gently and slowly swab the inside the nostril progressing to sinus opening...STOP at this point if fearful or severe swelling of the sinus opening prevents further insertion. I continue very gently until about half the cotton tip swabs around the sinus opening. STOP and remove. Bit of a very mild peppery sensation. Be prepared for sneezing to clear sinus. Sometimes a 2nd swabbing is needed to clear the mucous. Some folks to which used my tip, used a second swab soaked in warm water for a final rinse swabbing...same results
Just last last week, woke in the middle of the night..had one nostril so inflamed it almost totally blocked breathing. Did the swabbing on both nostrils, gargled with diluted peroxide solution. Went to bed breathing normal and slept peacefully. Caught it early and nipped it in the bud. Waiting longer, sometimes another wash out is necessary.
Some 15 years and it's worked every time...don't know if the early flu symptoms can be treated this way...but never had the flu in the same period. Too simple to believe but it does work for me. YMMV. Suppose a nasal syringe would also work with a diluted solution, but I leery about getting one sanitized enough. Good health to you.
You’re the second person who has mentioned this; I had never heard of it but will remember it.