My wife has heard the fuss about nasal rinses. She bought one of the various kits from Costco. It went under the sink and was forgotten about.
I actually developed a real infection of the lungs, throat, sinus, etc. I figured I would try the kit.
My baseline:
After a bad sinus infection starts to clear, you get the terrible drainage.
My results: It flushed out the snot in my nose, but didn't actually flush out my sinuses. It seemed to be a placebo for people with an urgent need to "treat" themselves. I kept using it every day as it instructed, it neither shortened the duration of infection (which makes sense, your body has to fight off the infection), nor did it flush the crud out that drains afterward.
Call me unimpressed. Plus, some scientific thinking says that using such a device as preventative care, is actually worse for you since you strip away protective mucus (DUH).
But, but... I used it and didn't get sick! Then you know what, you probably wouldn't have gotten sick anyway.