I had a chronic sinus infection for 9 years. Desperate to get rid of it, I bought a box that emits electricity on a frequency that allegedly kills bacteria and parasites. I held the box to my face for 7 minutes three times per day, and after a few days, the sinus infection was completely gone. After so many years of not being able to breathe/smell, that box was a miracle for me.

The box was invented by Hulda Clarke back in the 40s or 50s, and someone posted the plans for her box online so anyone can build them. Unfortunately, the company I bought my box from is out of business, but if you do a search for Hulda Clarke technology, you'll find lots and lots of companies selling them.

Edit to add: prior to my finding the box, colloidal silver was what worked best for me at keeping the sinus infection under control... but the colloidal silver never 100% got rid of it for me.