Xylitol is great! I can't stop eating these -- https://www.amazon.ca/Xyla-Brand-Xylitol-Raspberry-Candies/d.... And, indeed, they help, rather than harm, your teeth, and discourage bacterial sinus infections.

Which reminds me of a rant:

You know what doesn't do either of those things? Any mouthwash you can buy in the mouthwash aisle.

Ask a dentist about mouthwash. They'll recommend it—but only because the alcohol temporarily shrinks your gums, which allows a toothbrush and/or floss to scrape plaque out that was embedded deeper between the gum and the tooth. Mouthwash doesn't kill bacteria. (Or, it does, but only for the 30 seconds it's in your mouth—meaning that you'll have just created a power-vacuum that other, worse bacteria from e.g. the back of your throat can intrude into. And now the alcohol has also dried out your mucous membranes!)

If a dentist needs to prescribe you a mouthwash, on the other hand—for example, to keep a wound inside your mouth clean post-surgery—they'll prescribe something with ingredients completely unlike that in "regular" mouthwash. Here's (https://www.amazon.ca/Chlorhexidine-Gluconate-Antiseptic-Pep...) an example of one.

The primary ingredient of "mouthwash that actually works" is chlorhexidine—that's a chemical more commonly used as a surgical antiseptic (i.e. a "scrub" doctors will sanitize their hands with before putting them inside your body.) Conveniently, the fact that it's safe to touch your internal organs with, also means that it's safe to touch your mucous membranes with. (Though it's not entirely safe; it says stringently on such mouthwashes not to swallow any—but not because it'd harm you per se, just that it'd likely kill your intestinal flora in much the same way an antibiotic would.)

Interestingly, chlorhexidine and xylitol work in similar ways—they're both things bacteria intentionally take up into themselves, that then destroy the bacteria from the inside. Xylitol just stalls the bacteria's metabolism, starving it to death; while, IIRC, chlorhexidine throws off the bacteria's osmotic regulation until it pops, much like highly-saline environments do—but without doing the same to animal cells. Unlike xylitol, though, chlorhexidine will stick around in the mucous membranes (until you do any of the stuff I mentioned in the previous post) for eight hours, protecting you all the while. It's great. Everyone should use it, at least at night.

It's kind of weird, given all this, that it's not well-known, and not used in regular mouthwashes, no? Well, much like you just can't convince some people that a HWRNG-seeded CSPRNG is a valid source of OS entropy, you just can't convince some people that long-term chlorhexidine use wouldn't result in bacterial resistance—even though, in both cases, if there was any potential for it to fail in "normal" use (OS entropy; mouth-washing), it would have failed a long time ago in the "heavy-duty" use-case where it's already being used (cryptography; surgery.)

Or, to put that another way: if doctors will put chlorhexidine on their hands every day without worrying about growing MRSA under their fingernails, you can put it in your mouth every day without worrying about growing MRSA in your throat.

(Bonus pleasant fact: most prepared chlorhexidine mouthwash solutions are sweetened with xylitol. So you're getting a double-effect from that.)

On the other hand, prepared chlorhexidine mouthwash isn't very cheap (the one I linked above was $15 for a bottle that'll last less than a month), and preparing such a mouthwash yourself from concentrate is really a hassle (pure 2-4% chlorhexidine gluconate is much cheaper, but just diluting it with water/alcohol would create a solution that only retains potency for ~1 day; you'd need to add other chemicals to make it shelf-stable.)

But, if you can't (or just don't want to) get chlorhexidine mouthwash, I still wouldn't recommend using alcohol-based mouthwash. For battling gingivitis or a canker sore or whatever else, Xylitol actually works pretty well as a "quick-fix" alternative. That is, it works well if you exploit the very property I mentioned before—increased mucous-membrane absorption and retention under dehydration. So, here's a "life hack":

• Go buy a box of xylitol sweetener packets (the kind you'd pour into coffee. You can probably find them sorted into the "nutrition products for diabetics" area of a drug store.)

• Before you sleep, brush your teeth, floss, swish with water, spit. And then...

• Dump one of those xylitol sweetener packets directly into your mouth, not dissolved in liquid or anything. Spread it around; get it onto the insides of your lips, onto your teeth, etc.

• Let it absorb. Don't swallow it; just let it sit.

• Go to sleep, just like that.

That will protect your mouth, at least a little. Far more than Listerine ever would.

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Oh, and as a separate thought: if you have recurring canker sores, oral thrush, throat/sinus infections, ear infections, etc., despite good oral hygiene—there's likely a "hidden fortress" of bacterial biofilm somewhere out of reach, probably your maxillary sinuses or adenoids or Eustachian tubes. These areas are "safe" for bacteria because they're damp from breathing, but few actual fluids reach them.

Want a permanent solution? Flush them out. For the nose, I see people trying nasal lavage ("neti pots" et al), and for the ears, I see people going to an ENT to get microsuction. Neither of these are really needed. The biofilms aren't invincible; they're just dry—too dry for your body's natural defences to loosen them. Drip a few drops of mineral oil down your nose/into your ears, once per day. After two days, you should start to feel the need to clear your sinus passages by snorting, inwards. Just keep doing that. And voila, the hidden fortress has been destroyed.