The 2 most popular flavors of mouth sores are a Herpes virus (not THAT one, just a less embarrassing but nevertheless annoying relative) and something called "apthous ulcers" that are mysterious, meaning that doctors mumble and aren't sure if they are or not, but think if they say "apthous" you'll be impressed.
The main difference, from a practical standpoint is that the herpes ones are caused by a virus, and can be controlled with acyclovir if they're inside your mouth, and on the outside, over-the-counter Abreva actually works better than acyclovir, for reasons that are mysterious.
Lots of people have the virus, and it can lie dormant for years, decades, and then appear for any or no reason, though stress, emotional or mouthical - as in the dentist visit, where they're pulling on your lips, etc, is notorious for causing flare-ups.
If you tell the dentist you get them, she will just start giving you some acyclovir along with your new toothbrush every time you go.
So the easiest thing to do is to hope it's the virus one, say you think it is, and ask for acyclovir.
Now this is not particularly comforting, but the acyclovir will not necessarily just stop the current attack in its tracks. It can, however, lessen the duration, and it will definitely make Mr Herpes think twice before he pops up again - for a while.
If you have the virus, and it begins acting up, the best way to keep it out of your life is take a course of acyclovir 3-4 times a year for the rest of your life.
If it's apthous ulcers, and NOT Herpes, then the acyclovir will have no effect on it whatsoever, and you will need to ask for steroids.
Of course, if you have diabetes, you can only have topical steroids, not swallow-pill ones, so you're SOL, unless it's outside on your lips, which apthous ulcers seldom, if ever, are.
Either way, ask for a little bottle of lidocaine you can dab on with a Q-tip to control the pain.
There are also special mouthwashes you can get, that are very expensive. The active ingredient almost all of them have in common is called hydrogen peroxide.
You can also buy one of those expensive mouthwashes, or you can buy a bottle of hydrogen peroxide for 50 cents at the CVS, mix it with water yourself, and use the $20 you saved to buy more
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