Colloidal Silver would kill bad and beneficial bacteria. It may even kill fungi. I have used Colloidal Silver , in a nasal spray pump, to help with sinus infection. I works for a while; but I think the fungi are just overwhelming and have hiding places inaccessible to the spray. Or else, the infection has gotten deep into the tissues. I like the idea of putting drops of probiotics in the nose. I'll try that the next time.