Two Weeks Is the Line for a Mouth Sore

Somebody finds something in their mouth, holds a phone up to the mirror, and writes six words:

Just noticed this as well. Freaking out a bit. r/askdentists

That reaction is the normal one. It’s also, in most cases, unnecessary — and there’s a simple number that would have saved the panic, which almost nobody has ever been told.

The number is two weeks

An ordinary mouth ulcer heals on its own. No treatment, no gel, no rinse. A dentist answering one of these posts gave both the diagnosis and the timeline in a single sentence:

Appearance is a canker sore, it should go away within 2 weeks on its own. r/askdentists

Another said the same thing about a patch on a tongue:

These could be mouth ulcers. They’re completely harmless and sometimes do appear on the tongue. Give it a week or two and they should be gone. r/askdentists

So the rule is: a sore that is still there after two weeks gets looked at. Not because two weeks means something is wrong — the overwhelming majority of things that last longer are still harmless — but because two weeks is where looking at it yourself stops adding information.

This cuts both ways, and both directions are useful. Before two weeks, you almost certainly don’t need to do anything. After two weeks, waiting longer isn’t a strategy.

The four questions

Read enough of these threads and the same four questions get asked, by different dentists, of different people, about completely different things in their mouths:

Has the texture changed? Has it increased in size? For how long has it been there? Is the colour uniform or does it vary within the patch? r/askdentists

That’s the whole triage, and it’s worth understanding why each one is on the list.

How long. Everything above. Time is the single most informative fact, and it’s the one people almost never have, because nobody notices the first day.

Texture. A soft sore that stays soft behaves differently from one that firms up or roughens. Change is the signal, not the starting state.

Size. Something that stays the same size for a month is a different object from something that has doubled.

Uniform color. A patch that’s one shade throughout reads differently from one that’s mottled — light in places, darker in others, with an irregular edge. This is the question people are least likely to think of on their own.

The useful thing about that list is that it’s answerable at home, tonight, without any equipment. Take a photograph. Take another one in a week. Then you have the answer to two of the four, instead of guessing.

The one place with a shorter fuse

Location changes the threshold, and one location changes it a lot:

The side of the tongue is considered to be a “high risk” area for oral cancer. This needs to be biopsied immediately. r/askdentists

The lateral border of the tongue — the side, where it meets the teeth — is where oral cancers most often turn up. So does the floor of the mouth, underneath the tongue.

This does not mean a sore there is bad news. It means the same sore gets checked sooner there than it would on the inside of a cheek, because that’s where the odds shift.

If you’re going to remember one thing about geography: the side of the tongue is the place not to wait on.

Most of the time, the answer is nothing

It’s worth reading what the reassuring replies in these threads actually sound like, because they’re the majority and they never go viral:

Nothing super alarming. Not cancer. If there’s an oral medicine specialist in your area pay them a visit for your peace of mind. r/askdentists

Note what that reply does. It says not cancer, and then still suggests being seen. Those aren’t in tension. Peace of mind is a legitimate reason to have something looked at, and it’s the reason most people are actually there.

There’s also a version of this that’s more common than anybody admits, and one dentist named it directly:

You are super focussed on cancer, but your oral health is also a huge risk to your overall health. r/askdentists

Fear is a narrow lens. Somebody spending three weeks examining a spot on their tongue is often not looking at the gum disease that is quietly doing more damage in the same mouth.

Why nobody can just tell you

The part people find hardest to accept is that looking isn’t enough, and it isn’t enough for specialists either:

Looks like squamous papilloma but they are correct there’s no way to know for sure without the biopsy. r/askdentists

That’s an expert opinion that ends in I don’t know. Which is the honest answer, and the reason the whole system runs on biopsies rather than photographs.

So the useful question isn’t what is it. It’s does this need a biopsy — and that’s the question the four questions above are for.

If you need it looked at and aren’t getting anywhere

The single most upvoted piece of advice in this entire corner of the internet isn’t medical at all. It’s a script:

I would politely but firmly ask for a referral to an oral surgeon to have that removed and biopsied. r/askdentists

Politely but firmly. People undersell their own symptoms in the room and then leave without the referral they went in for. Saying the specific words — I’d like this biopsied — changes the conversation, and it is a completely reasonable thing to ask.

The short version

Under two weeks, an ulcer is almost always just an ulcer, and it will close by itself.

Over two weeks, get it seen — sooner if it’s on the side of the tongue, if it’s growing, if the texture has changed, or if the color isn’t even.

And take a photograph today, because how long has it been there is the question you’ll be asked, and it’s the one nobody can ever answer.