From my cite above: "Avoid abrasive foods like potato chips and pretzels; acidic drinks such as lemonade or orange juice; chocolate, nuts, lemons, figs, tomatoes, apples, pineapples, strawberries, shellfish, soy vinegar and beer that trigger canker sores in susceptible people . "
Just the opposite, then. Don’t do this.
Baking soda. Just pile it on.
In my personal experience, the only remedy is to catch up on sleep. (I only get them when I’m tired from many days of insufficient sleep.) YMMV, obviously.
Acyclovir has some use in viral infections, including herpes. Trouble is, most mouth ulcers are probably not cuased by viral infections. I would certainly not be in a hurry to use acyclovir (valtrex). I sometimes prescribe “magic mouthwash” – that is I get a willing pharmacist to mix some maalox or mylanta, viscous lidocaine, benadryl and carafate. People say it helps – but the reality is that steroids and tetracycline are as good as anything, and most treatments are unproven. Read up on the topic here.
From the above link (I really like the e-medicine site),
Medical Care: Identify and correct predisposing factors for RAS (e.g. canker sore). Ensure that patients brush atraumatically (eg, with a small-headed, soft toothbrush) and avoid eating particularly hard or sharp foods (eg, toast, potato crisps) and avoid other trauma to the oral mucosa.
SLS (sodium lauryl sulphate, as mentioned above) should be avoided if implicated as a predisposing factor. Any iron or vitamin deficiency should be corrected once the cause of that deficiency has been established. If an obvious relationship to certain foods is established, these should be excluded from the diet. Patch testing may be indicated to reveal allergies. The occasional patient who relates ulcers to her menstrual cycle or to use of an oral contraceptive may benefit from suppression of ovulation with a progestogen or a change in the oral contraceptive. Causal drugs should be excluded.
In most cases, the natural history of RAS is one of eventual remission. However, for some patients, remission occurs spontaneously several years later; thus, treatment is indicated in these patients if discomfort is significant. Relief of pain and reduction of ulcer duration are the main goals of therapy. Objective evidence shows the most efficacy from corticosteroids and antimicrobials used topically.
Topical corticosteroids (TCs) remain the mainstays of treatment. A spectrum of different TCs can be used. At best, TCs reduce painful symptoms but not the rate of ulcer recurrence.
The commonly used preparations are as follows:
Hydrocortisone hemisuccinate pellets (Corlan), 2.5 mg
Triamcinolone acetonide in carboxymethyl cellulose paste (Adcortyl in orabase, Kenalog), administered 4 times daily
Betamethasone sodium phosphate as a 0.5-mg tablet dissolved in 15 mL of water to make a mouth rinse, used 4 times daily
Hydrocortisone and triamcinolone preparations are popular because neither causes significant adrenal suppression; however, ulcers still recur.
Betamethasone, fluocinonide, fluocinolone, fluticasone, and clobetasol are more potent and effective than hydrocortisone and triamcinolone, but they carry the possibility of some adrenocortical suppression and a predisposition to candidiasis.
Topical tetracyclines may reduce the severity of ulceration, but they do not alter the recurrence rate. A doxycycline capsule of 100 mg in 10 mL of water administered as a mouth rinse for 3 minutes or tetracycline 500 mg plus nicotinamide 500 mg administered 4 times daily may provide relief and reduce ulcer duration. Avoid tetracyclines in children younger than 12 years who might ingest them and develop tooth staining.
Chlorhexidine gluconate mouth rinses reduce the severity and pain of ulceration but not the frequency.
Anti-inflammatory agents can help; a spectrum of topical agents such as benzydamine and amlexanox may help. Benzydamine hydrochloride mouthwash, though no more beneficial than a placebo, can produce transient pain relief.
If RAS fails to respond to local measures, systemic immunomodulators may be required. A wide spectrum of agents has been suggested as beneficial, but few studies have been performed to assess their efficacy (or their adverse effects are significant). Thalidomide 50-100 mg daily is effective against severe RAS, although ulcers tend to recur within 3 weeks. Teratogenicity, neuropathy, and other adverse effects dissuade most physicians from its use.
Few, if any, of the other medications used for RAS have undergone serious scientific evaluation. These include transfer factor, gamma-globulin therapy, sodium cromoglycate lozenges, dapsone, colchicine, pentoxifylline, levamisole, colchicine, azathioprine, prednisolone, azelastine, alpha 2-interferon, ciclosporin, deglycerinated liquorice, 5-aminosalicylic acid (5-ASA), prostaglandin E2 (PGE2), sucralfate, diclofenac, and aspirin.
Here’s my experience.
For my entire life, I got canker sores constantly. I always had 3 to 6 in my mouth at any given time, all of them very painful.
Several years ago, I started coming down with hives. My doctor put me on Claritin to do away with the hives, and it worked quite well. Something else happened, too: my chronic canker sores went clean away. At first, I thought perhaps that I had “aged out” of getting canker sores, and I stopped taking the Claritin to check this theory out. After a few days of no Claritin, the canker sores came back. I started taking it again, and after a week or two, they went away again. I’ve been on Claritin now for years and I almost never ever get a canker sore anymore. Once in a great while, I again try stopping taking the Claritin just to test it, and once again, the sores come back. Oh, and I got over whatever was causing the hives - those never returned.
So in my case, it looks like it was allergies, I suppose.
My favoured method for dealing with ulcers (canker sores? Bah)?
Bonjela Teething Gel.
Hubby introduced me to it. It’s a mild anaesthetic, and an antiseptic. So it stops the owies as well as helping heal the sore.
Usually if I have an ulcer and leave it on its own, it’ll take at least 5 days to clear up. Two to three days of Bonjela and it’s totally gone. Plus the anaesthetic is fun. You talk funny sometimes if you need to put it on the inside of your lower lip or somewhere that’s responsible for shaping vowels 
If you are caught out one evening or weekend with a mouth ulcer, and no way to get to a pharmacy to buy a remedy, one thing that has always helped me has been to make a cup of very strong, black tea.
As soon as the tea has cooled just enough to be able to hold it in your mouth, take a big mouthful and hold it in your mouth, swishing if you can. Then either spit or swallow, the choice is yours!
Do this for the entire cupful of tea, taking care to get good big mouthfuls and getting it all over your mouth, particularly over the ulcer, which will hurt but the heat will soon overcome the pain.
It will leave your mouth feeling clean and soothed, and the icky film on the mouth ulcer will be gone. Obviously this is a very safe method so you can use it as often as you feel you can stand another cup of tea!
I think it is the slight astringency of tea that helps. It also contains tannin, which I have heard is soothing for burns. Whatever, it can’t hurt and it’s better than doing nothing till you can get to a pharmacy.
I remember too, when I was a kid mum used to make me swish salt water for any mouth wounds - ulcers, cuts on the inside of my mouth, lost tooth sockets… I hated it.
I get these little bastards too – have gotten them all my life. Changing toothpaste didn’t help in my case. And I’ve never liked the Orajel-type teething medications because they seem (to me) to make the sores worse and make them last longer.
What I do is brush my teeth a lot. I find that the sores hurt less when my mouth is really clean. I brush my teeth real well, then rinse with a peroxide-based mouthwash. I do this 4 - 5 times a day. It hurts like hell, so part of the benefit may come from overloading the pain receptors, I don’t know.
I’ve used the sealing-stuff, also, and it does work. But it drives me crazy after a while, having that plastic ‘scab’ in my mouth. So I only use the stuff occasionally – before a meal (I always lose weight when I have a real bad sore, because I eat very lightly and rarely during a bad outbreak), or when I’m on my way to an appointment when I’ll need to talk.
Should you find yourself without the super-glue stuff again, do use a cough drop. Put it between the sore and your gum and keep it there until it dissolves. It won’t hurt the sore and you’ll get a nice anesthetic effect.
Garlic. I tend to bite the inside of my lip from time to time, and the resulting canker sores can be a real pain (heh). I have tried the salt treatment but never the Listerine. In my experience, I get better results with garlic. As with the salt and Listerine treatments, the garlic one stings a bit. (A bit? Its absolute torture - but worth every second.)
Either cut the end off a clove of garlic, or crush a clove in a garlic press. Carefully dry the canker sore with a tissue and apply the mashed garlic, or dab the canker sore with the cut end of the clove. The longer you can take the garlic on there, the more effective it will be. But don’t go overboard - no more than 30 to 45 seconds. Fresh garlic can actually be a little caustic on the inner lining of the mouth, and keeping it there too long can cause otherwise healthy tissue to burn and peel away.
As others have said with the salt or Listerine treatments, the pain from the garlic seems to completely overload the nerve endings, and when it’s all over the canker actually goes numb. Plus your spaghetti will taste really good.
After the treatment, the canker will usually form a whitish skin over the canker - a kind of scab as the canker begins to heal. I have had untreated canker sores (from accidentally biting the inside of my mouth) persist for two weeks. But I have also had canker sores begin to heal within a day after the garlic treatment, and they were gone without a trace shortly thereafter. Admittedly, some cankers didn’t respond as well as others to the garlic, but it is my standard treatment and more often than not, I get good results.
I’m at a loss as to why anyone would torture themselves with any treatment that causes more pain than the actual ulcer itself. I’m telling y’all, the antacid method is painless and works wonders. I believe in it so much I double posted about it earlier. 
Well, it’s like going to the doctor to get a shot. The shot might hurt, but it makes you feel better in the long run. Modern medicine is loaded with treatments that cause temporary discomfort in exchange for long-term relief.
But I’m certainly not going to turn away another treatment if it works just as well and is less irritating to boot. I wonder - does the antacid tablet provide the same numbing side effect as the garlic/salt/Listerine? I can tell you, that’s a pretty great feature of those treatments.
I’ll try the antacid idea the next time I’m faced with one of the little beasties. What have I got to lose?
Well, poo. The super-glue stuff did not help all that much, and today it’s just as bad as it was yesterday. I did try the Tums remedy, and that did seem to help–I’ve done it twice now and will go get another in a minute. I had a Cepacol too.
One weird thing is that the sore started off in the middle of my cheek and has moved all the way back to the back of the jaw. It’s just as big, it just moved, and it’s hard to get at with the medicine. Moving target canker sore, argh!
I guess I’ll lose a little weight this way–no sugar, no lemonade, 
and my dinner for two nights has consisted of corn on the cob and nothing else.
That’s likely just making them worse. The theory is that the SLS cleans the inside of your mouth too well, which gets rid of the living coating.
Really, dudes- try the yogurt/acidolpholous/probiotics. Painfree.
Thought I might as well chip in as well. Growing up I had cankers now and again. The remedy around my household was to apply some powdered alum. I don’t remember it being painful (though it might have smarted a bit). More noticeable was the astringent effect (which is the point, I gather). It tastes kind of nasty, but wow was it effective.
I pour salt on mine. It hurts like crazy, but seems to help in the long run.
No one has mentioned Duke’s Miracle Mouthwah??? Ask your doctor for a prescription.
This was advice given me by a pharamacist years ago, who said his son had chronic canker sores (although he played hockey, which might inicate other sources of the wounds): Buy L-Lysin, an over-the-counter dietary supplement, in the chewable form and let it dissolve on the sore. It seemed to work for me.