Mouth sores keep coming back
One sore heals. A week or two later, a new one shows up. These small round ulcers sit inside the lip, inside the cheek, or under the tongue.
This pattern has a name. Doctors call it recurrent aphthous stomatitis. Most people just call them canker sores.
Some people get three or four a year. Others barely get a break between them. Either way, the cycle is common and it is not your fault.
A canker sore is not catching. You did not pass it to anyone, and no one gave it to you.
When to see someone
See a dentist if a sore lasts more than two weeks.
Go sooner for a hard lump or a white or red patch. A sore that does not hurt is also a warning. A dentist can check for mouth cancer.
Call your doctor if sores come with a fever, a rash, or sore red eyes. Call too if you get sores on the genitals. That mix can point to Behcet's disease.
Go to urgent care if the pain stops you from drinking. You can dry out fast that way. Kids dry out faster than adults.
Book a doctor if new sores arrive month after month. Ask for a blood test for iron, folate, B12, zinc, and vitamin D. Ask about a celiac test as well.
Call your doctor if belly pain, loose stools, or weight loss come with the sores. That points to the gut, not the mouth.
See your dentist if the sore lands in the same spot each time. A sharp tooth or wire may be rubbing it raw.
Why it happens
Your immune system turns on a small patch of tissue inside your mouth. The top layer breaks down. What is left is a shallow pit over raw nerve ends.
No one knows the exact switch that starts it. Some people seem primed for it from birth. If a parent got them, you are more likely to get them too.
Triggers then push that primed system over the edge. Stress and poor sleep are the two big ones. A cheek bite, a sharp tooth, or braces can start one as well.
Hormone shifts before a period set some people off. So do acid foods like citrus, tomato, and pineapple. Toothpaste with SLS in it can thin the lining and make sores easier to start.
Low levels of iron, folate, B12, zinc, or vitamin D show up this way in some people. That is why a blood test is worth asking about when sores keep coming back.
What else it could be
Not every mouth sore is a canker sore. The right fix depends on the cause. Here is how they differ.
Cold sores are the most common mix-up. They start as a cluster of tiny blisters. They sit on the outside of the lip or near the nose, not inside the cheek.
Canker sores are round or oval. They have a white or gray center and a red rim. They sit on soft tissue inside the mouth, and they are not catching.
A sore in the same spot each time may be a rub. A sharp tooth, a rough filling, or a braces wire can do it. It heals for good once a dentist smooths the edge.
Oral lichen planus makes white lines like lace inside the cheek. Sore red patches often come with it. It lasts months, not days.
Thrush is a yeast growth. It looks like white curd you can wipe off. Under it is a raw red spot.
Hand, foot and mouth disease hits young kids most. Mouth sores come with a rash on the hands and feet. A fever often comes first.
Behcet's disease causes mouth sores plus sores on the genitals. Eye pain or red eyes can come with it. That mix needs a doctor, not a home remedy.
Crohn's disease and celiac disease can show up as mouth sores. Watch for belly pain, loose stools, or weight loss. A doctor can test for both.
One sore that does not heal in three weeks is its own thing. A hard lump or a patch that does not hurt matters most. Get that looked at, even if the rest of your mouth is fine.
How to read the grades below
The options below come from our page on Canker Sores. Each one carries two labels.
The first label is the evidence grade. A means strong trials in people, B means smaller or mixed studies, and C means early or limited findings. D means lab work only, and “insufficient” means the research cannot settle it yet.
The second label is the traditional tier. T3 means long use in more than one tradition, T2 means long use in one, and T1 means known use. T0 means no such record.
These grades come from research on Canker Sores, the parent Health Topic, not on mouth sores keep coming back.
A grade tells you how strong the research is, not how well something will work for you. Talk to a doctor or pharmacist before you start anything, above all if you take other medicines.
What to try first
Start with a salt water rinse. It has an evidence grade of A and a traditional tier of T3. Mix half a teaspoon of salt in a cup of warm water.
Swish for 30 seconds, then spit. Do this two or three times a day. It may sting for a moment.
Next, coat the sore so food and air do not touch it. Hyaluronic acid gel has an evidence grade of A. Aloe vera topical has an evidence grade of B and a traditional tier of T3.
Licorice root has an evidence grade of B and a traditional tier of T3. It comes as a patch or a rinse. Skip it if you have high blood pressure.
Curcumin has an evidence grade of A. Berberine has an evidence grade of A. Both are used as a gel or rinse on the sore, not swallowed.
If sores keep coming back, ask for a blood test. Vitamin D has an evidence grade of A. Zinc has an evidence grade of A.
Those two seem to help most when your level is low. Vitamin B12 has an evidence grade of insufficient. A whole food multivitamin also has an evidence grade of insufficient.
Some people try options with thin proof. Propolis has an evidence grade of insufficient. Sage has an evidence grade of insufficient and a traditional tier of T3.
Beta-glucan has an evidence grade of insufficient. Acupuncture has an evidence grade of insufficient and a traditional tier of T3. Folk use is long for some of these, but the trials are too few to judge.
Probiotics (Lactobacillus plantarum P8) has an evidence grade of C. That means the proof is weak but real.
Two free changes are worth a try. Switch to a toothpaste made without SLS. Some people find that easing off acid foods while a sore heals makes it more comfortable; it is worth trying.
How long it takes
A small canker sore heals on its own in 7 to 10 days. A large one can take 2 to 6 weeks. Big ones sometimes leave a small scar.
Rinses and gels work on pain, not speed. Most people feel less sting within a day or two. Keep using them until the sore closes.
Fixing a low vitamin level is slower. Give it 8 to 12 weeks before you judge it. You are looking for fewer sores, not a faster heal.
Trigger changes need time too. Track your sores on a calendar for three months. That is how a pattern shows itself.
