I used to wash out my SinusRinse syringe with rubbing alcohol.  Because
my sense of smell is shot when I get a sinus infection, I once made the
mistake of mistaking the alcohol in the syringe for water and I shot all
the alcohol up into my nose.  It took my nose several days to get over it.

Another time, I found that an insect had crawled inside it and I almost
squirted it into my nose too.

Ever since, I've gotten into the habit of rinsing the syringe out with
water BEFORE using it on my nose, as a precaution.

No, it now appears that the majority of sinus infections are viral,
especially the ones that set in after a viral cold or the ones that hit
in the colder months of the year.

My ENT has his pet "Unified Field Theory of Sinusitis":  The upper and
lower respiratory tracts all have the same binding sites on which
viruses can attach.  Hence it's useless to talk about a "viral cold"
anymore as if it doesn't affect the rest of the respiratory tract.
Endoscopy clearly shows that in most simple colds, the sinuses are
invariably infected too, contrary to what they used to teach in medical
school.

As far as my ENT is concerned, it's a viral GENERALIZED RESPIRATORY
INFECTION and it can strike any or all parts of the respiratory system
at any time.  The different names we use:  cold (rhinitis), sinusitis,
laryngitis, tracheitis, bronchitis--should just be thought of as
describing localized SYMPTOMS, but it's all the same infection and it
can infect any or all of the above as the viruses spread.

That would explain why roughly half of all acute sinus infections
resolve spontaneously in a few weeks without antibiotics, and why
antibiotics are only marginally more helpful.  Because many of the
infections were probably viral anyway.

Eventually, your immune system will get a handle on it (unless you have
some kind of immune disorder).  Unlike bacteria, viruses don't multiply
in the mucus, but in the cells of the tissues themselves.  So drainage
of the mucus isn't the issue for a viral infection.  Whereas for a
bacterial infection, the bugs can just keep multiplying in the stagnant
mucus indefinitely till the sinuses are opened and the mucus is drained.

Viral infections are invariably self-limiting in otherwise healthy
people.  If it goes away in less than a month, it was viral.  If it
lingers and lingers or seems to get worse over time, it's probably
bacterial.

And while it's not 100% sure, viral infections tend to have a sudden
onset because of how rapidly the viruses multiply--I'm sure you've
noticed how a cold seems to start out of nowhere with a sudden scratchy
throat.  Whereas a bacterial infection comes on gradually and gets a
little worse each passing day.

Ellen,
 I have to agree that I'd never share a neti pot. I like the porcelin
ones from Whole foods, because you can throw them in the dishwasher.
 I use the plastic ones for travel, and actually both my daughters
use them at college. They got over the yuck factor, when they
discovered they felt better and weren't catching the virus de jour.
Judy