How to treat canker sores according to science

tl;dr: if you keep getting sores on your tongue and the inside of your lips, try vitamin B12 supplements for several months.

Canker sores are one of the petty banes of my existence.

I’ve gotten them ever since I was a kid. I wake up one day with a little white ulcer on the inside of my lip or on my tongue. By the next day, they hurt like hell. I can’t eat anything spicy, or sour, or salty without Satan himself jabbing his pitchfork into my mouth. 

If the sore is on my tongue, every time I talk it also hurts. I end up mostly mute and miserable for 5 days, cursed to have people continually ask me, “Why are you talking so weirdly?” and me continually respond, “Because I haf a thore on my tung.”

Over the years, I’ve half-heartedly looked for cures and preventatives. I have noticed that I often get sores where I’ve already damaged my lip or tongue, but that doesn’t seem to be always true. As a scientific explanation, happens sometimes but not always isn’t a particularly good one, and it’s very hard to prevent myself from getting any abrasions in my mouth whatsoever.

After my most recent bout with canker sores, I decided to finally put in proper effort into researching it. Here’s what I found.

A note on terminology

First of all, canker sores are the American name for it. The “canker” part of it comes from “cancer”, which comes from back when any ulcer was seen as a tumor. So, the American name is “cancer sore”, which is a dumb name.

The technical term for them are aphthous ulcers. This is also a dumb name, as aphthous means “ulcer” in Greek, so this is just “ulcer ulcer”. Nowadays, “aphthae” refers to any mouth ulcer.

Finally, the repeated formation of aphthous ulcers is called “aphthous stomatitis”. Stomatitis is “inflammation of the mouth or lip”. So the repeated formation is “mouth ulcers related to inflammation of the mouth or lip”. It’s a slightly better name.

I’ll be using any of these terms interchangeably, but they tend to use aphthous stomatitis in the medical literature.

The cause of canker sores

The cause of canker sores is…unknown.

Sorry guys! Essay over.

Just kidding. You’ll actually see that on Wikipedia, but I think it makes more sense to say canker sores are a symptom, and they can have a variety of causes. You see, aphthous ulcers look like this:

Thanks Wikipedia!

You’ll notice there’s a red outline, then a white covering. Now, take a look at this chemical burn from an herbal preparation on a palate:

Thanks Hindawi!

Pretty similar, right? Red surrounding a white film. There’s only a limited number of ways that your body can resolve oral injuries. Ulceration is one of them.

So aphthous stomatitis can be caused by anything that causes an ulceration response. That includes physical trauma, smoking, bacterial infection, autoimmune disorders, nutritional deficiencies, and stress. 

Now, what’s frustrating is that none of these can guarantee a canker sore. Ultimately, that depends on your body’s wound healing and immune response, which is still a mystery in a lot of ways (and that I’ve written a lot about). There are probably genetic and environmental contributors, but no smoking guns.

However, there have been some intriguing treatments for canker sores, which do suggest some other contributors for aphthous stomatitis. I’ll discuss those now.

Treatments for canker sores

What doctors will give you

The treatments for canker sores that doctors will give you involve anti-inflammatories or numbing agents. I’ll cover those quickly because they’re not that interesting, with the help of this review article.

First-line treatments are simple numbing agents, like benzocaine (which you’ll find in Orabase), or nonsteroidal anti inflammatory drugs like diclofenac.

More serious cases get more serious immunomodulatory treatments like glucocorticoids and tetracycline. Really serious cases get the big guns of immunosuppressants like thalidomide (yes that thalidomide, the one with the birth defects).

Alternative treatments

These are more fun. There are a couple weird ones that I want to cover, and I’ll end with the one that I think is the most plausible.

Vitamin C

The first is ascorbate, or vitamin C. Vitamin C has a long history of being used in immunomodulating or immune system supporting conditions. Some people swear that vitamin C helps the common cold, but most studies haven’t borne that out. Linus Pauling famously believed that it helped cure cancer, which, again, studies really haven’t borne out.

So, Vitamin C isn’t starting off on a great foot. Deficiency in vitamin C is definitely bad (and eventually leads to scurvy), but it’s not at all clear that extra vitamin C leads to anything good.

The only thing I’d say in vitamin C’s defense is that Linus Pauling advocated for intravenous supplementation vitamin C, which doesn’t have the same upper limits on concentration in the bloodstream that oral vitamin C does. Most of the studies debunking vitamin C have been done on oral vitamin C, which means that maybe, just maybe, the issue with the studies was that effective supplementation of vitamin C needs to reach a level higher in the bloodstream than possible with oral supplementation. Maybe.

Anyways, this was most likely the thought process behind why a Japanese team tried to use oral vitamin C to treat aphthous ulcers, despite the well-publicized failures. They may also have been aware of the successes of topical vitamin C in corneal ulcers. And, although they didn’t know this, they presaged the limited success of oral vitamin C in foot ulcers.

So, with that being said, the Japanese team did see a pretty great result in using vitamin C in aphthous ulcers, reducing the incidence of ulcers from 4 to almost 0 in their treatment groups. Unfortunately, they did this while running an incredibly shoddily designed trial, with zero blinding, patient self-reporting, and a very small sample size of 24.

My overall recommendation for vitamin C then is pretty equivocal. Vitamin C definitely will not hurt. Will it help? Eh…maybe.


So, technically, this is “low-level laser therapy”. The idea is that lasers are shone onto the ulcers and then they heal. It’s not just any lasers though. It’s specific lasers at specific wavelengths and frequencies. So…science!

I’m going to say off the bat that this probably doesn’t work. It was done in Bulgaria, supports itself with papers from Bulgaria, has zero mechanical reason why it should work, has zero blinding or placebo, and the lead author clearly has a thing for lasers. Oh, also, when they do cite papers from more mainstream sources, they conveniently ignore the big review paper that said low-level laser therapy has no effect on wound healing that shows up at the top of Google’s search results.

But, on the other hand, it’s fun. So let’s talk about it. According to them, after they shine lasers on the ulcers, they heal in 2 days. These have to be special lasers. This works, allegedly, way better than pharmacotherapy.

The cost? Only $2500 (at least in the US)! So, each time you get an aphthous ulcer, you can look forward to shelling out $2500.

Net-net, probably not a great treatment.

[Note: you can also find papers from India and Brazil about this, but they’re not much better]

Vitamin B-12

This is actually my favorite study. Spoiler alert, sorry.

Now, first of all, it saw positive results: over the course of 6 months of supplementation of 1000 mg sublingual B12, the average duration of aphthous stomatitis was decreased from 11 days to 2 days, and the number and pain level of aphthous stomatitis saw similar decreases.  More importantly, this study was actually done well : it was a randomized, placebo-controlled, double-blind trial attached. They even checked to make sure the patients actually took the pills by looking at their bottles.

Other studies have seen similarly good results (1, 2, 3). There are even suggestions of vitamin B12 deficiency being linked to H. pylori infection, which is the cause of gastric ulcers (although there’s controversy over whether H. pylori can be a cause of aphthous ulcers). 

If I were to recommend any treatment for canker sores, it’d be this one. In fact, over the course of researching this article, I got a giant tub of B12 from Kirkland Signature for $12.65 from Amazon (not an affiliate link). I’d recommend you do the same.

The conclusion

I think it’s reasonably certain that vitamin B12 does help with canker sores. But why?

Here’s where I start speculating wildly (so be forewarned).

B12 is a crucial vitamin for production of red blood cells. Lack of it causes megaloblastic anemia, which results in red blood cells not being able to mitose.

Supplementing with B12 may allow for more rapid production of red blood cells, allowing for more efficient healing processes than ulceration.

Is this true? I have no idea. But it sounds legitimate, and nobody else has a better idea (seriously, even the papers on aphthous ulcers just throw their hands up when they’re asked for a causative mechanism).