Canker Sore Remedies: What Actually Works, at What Dose, and What to Skip

Most pages about canker sores tell you the same three things: rinse with salt water, avoid spicy food, and correct any deficiencies. Then they stop.

This one does the part they skip. It grades the nutrients the way a clinician grades a drug, with the study population, the exact dose, the duration, and the real numbers, including the one well-run trial that found no benefit at all. You will finish knowing what a canker sore is and is not, how long it lasts, which remedies carry real evidence, and when an ulcer deserves a professional look.

What a Canker Sore Actually Is (and Is Not)

A canker sore is a shallow, round ulcer on the soft tissue inside your mouth. You usually find one on the inside of your lip or cheek, on the tongue, or under the tongue. When the pattern repeats, clinicians call it recurrent aphthous stomatitis.

Three things a canker sore is not matter as much as what it is. It is not contagious, so you cannot pass it on or catch it. It is not herpes, and it is not a cold sore. And while a single canker sore is usually not a sign of something serious, a repeating cycle is worth investigating with a clinician.

The tell is location and shape. A canker sore sits inside the mouth, on loose, movable tissue, with a pale center and a red rim. It hurts most when you eat, drink, or talk.

For context, a 2009 trial put the frequency of recurrent aphthous stomatitis at up to 25 percent of the general population, and a 2012 trial described it as affecting more than 2.5 billion people worldwide. Both figures come from the trials themselves.

If the raw feeling is in your throat rather than a single spot in your mouth, that is a different problem. Our guide to sore throat remedies covers it.

Canker Sore or Cold Sore?

Half the confusion around canker sores comes from mixing them up with cold sores, and the mix-up matters because the two need different care.

• Canker sore. Inside the mouth: lip, cheek, tongue, or under the tongue. Not contagious. Not caused by herpes.
• Cold sore (fever blister). Outside the mouth: outer lip, skin around the mouth, or nose. Contagious. Caused by herpes simplex virus type 1 (HSV-1).
• The practical test. A sore on the pink skin outside your lip is a cold sore. A sore on the wet tissue inside your mouth is a canker sore.

Because HSV-1 drives cold sores, they respond to a different set of remedies. Our guide to cold sore remedies walks through what helps an outbreak on the lip.

Getting the distinction right prevents a common mistake. Lysine belongs in the cold sore conversation, not in a canker sore article, and this article returns to that later.

The Three Types and How Long Each Lasts

Clinicians sort canker sores into three types by size and number. Knowing your type tells you how long the discomfort will last.

Minor Canker Sores

Minor ulcers are the everyday kind, the most common type, and the one most people mean when they say canker sore. They sit under about 1 cm across, and they heal in about one to two weeks without leaving a scar.

Major Canker Sores

Major ulcers are larger and deeper, and they are the least common type. They can take months to heal, often leave a scar, and are the ones most likely to interfere with eating and drinking.

Herpetiform Canker Sores

Despite the name, herpetiform ulcers are not herpes. They are rare clusters of many tiny ulcers that sometimes merge, and the crop usually heals within about two weeks.

Pain eases within a few days, and the ulcer usually heals within about two weeks. If a sore runs well past that window, stop waiting and get it examined.

What Triggers a Canker Sore

No single cause explains every canker sore. Researchers describe triggers that tend to repeat in the same person.

• Mouth injury. A toothbrush slip, a sharp chip of tooth, a dental procedure, or a burn from hot food can start one at the injury site.
• Acidic and spicy foods. Citrus, tomato, vinegar, and hot spices often appear in food diaries right before an outbreak.
• Sodium lauryl sulfate toothpaste. SLS is the foaming agent in many toothpastes and one of the most discussed triggers.
• Stress. Emotional stress is among the most commonly reported triggers, though it is hard to measure.
• Hormonal shifts. Some women notice outbreaks tracking with their menstrual cycle.
• Some medicines. Certain drugs, including some NSAIDs and beta blockers, appear in case reports as triggers.

Some people also carry a background that makes recurrent ulcers more likely. These appear in the research as associated conditions, not as the cause of every sore: celiac disease, inflammatory bowel disease including Crohn's disease, Behcet's disease, immune suppression, and a family history of the condition. If any match your history, raise them with your clinician. Our digestion and gut health library covers that list.

Triggers are personal, which is why the next step flips the question from what you ate to what your body is missing.

If You Keep Getting Them, Check These Four Things First

If you get canker sores two or three or more times a year, the highest-value move is not a remedy. It is finding out whether a measured deficiency is driving the cycle.

The case for testing is strong. A 2015 meta-analysis in the British Dental Journal pooled 9 case-control studies with 710 cases and 602 controls and found haematologic deficiencies significantly more common in people with recurrent aphthous ulceration. The combined odds ratios were striking:

• Folic acid: odds ratio 7.55 (95 percent CI 3.91 to 14.60).
• Vitamin B12: odds ratio 3.75 (95 percent CI 2.38 to 5.94).
• Ferritin: odds ratio 2.62 (95 percent CI 1.69 to 4.06).
• Haemoglobin: odds ratio 1.77 (95 percent CI 1.12 to 2.80).

A second, independent meta-analysis in BMC Oral Health (2024) examined the same condition and reached the same broad conclusion, which is what makes the association credible.

Which four markers belong on your list?

1. Vitamin B12. Ask for serum B12, and know that a normal level does not always rule out a shortfall at the tissue level. Tingling hands or feet, a sore or smooth tongue, and fatigue are the classic clues, and a vegan or restricted diet raises the risk. Our guide to B12 deficiency symptoms has the full list.
2. Folate. Folate works alongside B12, and it carried the strongest association of the four markers.
3. Iron and ferritin. Ferritin is the stored-iron marker and can run low before haemoglobin does. Fatigue and shortness of breath are the usual signals. Our iron supplements guide explains the numbers.
4. Zinc. Zinc supports normal immune function and tissue repair, and it is among the nutrients most studied in mouth ulcers.

The point of a screen is to replace guessing with a number. A low result means correcting that specific deficiency is well supported. A normal result is useful too, because it moves you from what am I missing to which add-ons actually have trial evidence.

The Nutrient Evidence, Graded

This is the section most pages skip. Each nutrient gets the same treatment a drug would get: who it was studied in, the dose, the duration, the result in real numbers, and a plain verdict.

Vitamin B12

The strongest single nutrient signal in this area comes from a 2009 randomized, double-blind, placebo-controlled trial led by Volkov. It studied 58 primary care patients, 31 in the treatment group and 27 in the control group.

The dose was 1000 mcg of sublingual vitamin B12 daily for 6 months. By months 5 and 6, ulcer duration, ulcer number, and pain were all significantly reduced. In the final month, 74.1 percent of the B12 group reached a no-ulcers status, compared with 32.0 percent of controls (P < .01).

One detail sets this trial apart from nearly every page that mentions it: the benefit held regardless of the participants' starting blood B12 level. It showed up even in people whose serum B12 was not low.

Verdict: the strongest single nutrient signal here, and the one most pages leave vague. If you pick one nutrient to understand first, make it B12. Form matters at purchase, and our guide to vitamin B12 forms compared explains methylcobalamin, cyanocobalamin, and the sublingual route. A methylcobalamin option is XYMOGEN, Methylcobalamin 60 Tablets.

Folate and Iron

Folate and iron sit right beside B12 in the deficiency research. In the 2015 meta-analysis, folate carried the strongest association at an odds ratio of 7.55, with ferritin at 2.62, and the 2024 BMC Oral Health review reached the same conclusion. Verdict: the association is strong, and the point is replacement, not blanket high-dose supplementation. Correcting a measured deficiency is well grounded; taking high doses when your levels are already normal is a weaker question.

Multivitamin

Almost no competitor page reports this finding. A 2012 randomized, double-masked, placebo-controlled trial led by Lalla studied 160 adults with at least three episodes of minor recurrent aphthous stomatitis in the prior 12 months. They took a once-daily multivitamin at 100 percent of the US reference daily intake (83 people) or a placebo (77 people) for up to 365 days.

The result was flat: no significant difference in mean new episodes, 4.19 versus 4.60 (P = .69), and no significant difference in duration, 8.66 versus 8.99 days (P = .60).

Verdict: a daily multivitamin at label strength is not prevention. The authors concluded that clinicians should not recommend a routine multivitamin as prophylaxis, the finding every competitor page omits.

Zinc

Topical zinc has real support. A 2020 randomized, double-blind, placebo-controlled trial led by Ghorbani studied 46 patients with recurrent aphthous stomatitis who received a zinc sulfate mucoadhesive tablet or a placebo for 7 days. Lesion diameter dropped significantly in the zinc group by days 3, 5, and 7 (P = .001), and pain differed significantly from day 4 (P = .001).

The honest caveat comes from a 2026 review by Kim on topical zinc for oral mucosal diseases. It covered 14 studies, only 3 on recurrent aphthous stomatitis, and only 2 of those were randomized controlled trials. Topical zinc reduced pain and ulcer size, but a significant difference appeared in only one of those trials.

Verdict: topical zinc is where the signal is, and swallowed zinc lozenges are a much weaker bet. The supportive trial used a tablet that sits against the ulcer, not a lozenge you swallow. Our guide to the best form of zinc covers what to look for. For a chelated oral form, XYMOGEN, Zinc Glycinate 120 Capsules is one we carry.

Vitamin D

The direct evidence for vitamin D and canker sores is thin. A 2026 review by Yesudian links lower vitamin D to reduced oral immunity and periodontal disease risk, and notes that B-complex deficiencies are associated with glossitis, angular cheilitis, and recurrent aphthous stomatitis.

Verdict: reasonable to correct if you test low, but the direct aphthous-ulcer evidence is thin. Do not expect vitamin D alone to change your ulcer pattern.

Topical Remedies That Have Real Trials

Nutrients work from the inside. Topical remedies work on the ulcer itself, and a few have genuine trials behind them.

Honey

Honey is the standout topical option, with unusually clean data. A 2014 randomized, blind, controlled trial led by El-Haddad studied 94 subjects with 180 minor recurrent aphthous ulcerations, split among honey (67), a topical corticosteroid (57), and an Orabase control (56). Honey was applied four times a day for 5 days.

Honey won on what matters: a significant difference favoring it on ulcer size, days of pain, and erythema (redness), with no side effects reported in any group. The 2022 network meta-analysis by Liu also ranked honey among the better topical options.

Verdict: strong, low-risk, and easy to try. A small spoonful applied directly to the ulcer four times a day mirrors the trial.

DGL Licorice

Deglycyrrhizinated licorice, or DGL, has a smaller, older evidence base. A 1989 study by Das gave 20 patients a DGL mouthwash and followed them for two weeks. Fifteen reported 50 to 75 percent improvement within one day, with complete healing by the third day.

Two caveats matter. The study was small, and it had no control group, so the improvement could reflect the natural course of an ulcer. Even so, the 2022 network meta-analysis ranked glycyrrhiza well among the better topical options.

Verdict: promising but unproven, best treated as a low-risk add-on. Do not let 15 out of 20 sway you more than the missing control group should.

Zinc, Topical

Topical zinc earns a second mention because it is a topical remedy first and a nutrient second. The Ghorbani trial above remains the cleanest signal here, and the 2026 caveat applies the same way: across the relevant trials, only one showed a significant difference. If you try zinc, choose a form that makes contact with the ulcer.

Salt Water and Baking Soda Rinses

These rinses do not heal an ulcer, and no trial claims they do. They offer symptom relief: they clean the area, reduce irritation, and make eating and drinking less painful. They are inexpensive and harmless.

The NHS gives a simple recipe. Dissolve half a teaspoon of salt in a glass of warm water, swish it around your mouth, and spit it out. Do not swallow it. A baking soda rinse follows the same logic and can feel gentler on a very raw mouth.

Probiotics and the Recurrence Question

Most remedies here target an ulcer you already have. Probiotics are different: the question they may help with is not how fast this heals but how long until the next one.

The best evidence is the 2022 network meta-analysis by Liu, pooling 72 trials and 5,272 subjects across 29 topical interventions. It recommended probiotics as the long-term option, for lengthening the ulcer-free interval and reducing recurrence. A separate 2021 randomized controlled trial by Aggour studied 60 adults and 60 children with minor recurrent aphthous stomatitis, using probiotic lozenges twice daily for 5 days. It found significant pain reduction in the adult subgroup, and significant ulcer size reduction plus lower outbreak frequency in the child subgroup.

Verdict: promising but early, with the strongest signal for recurrence rather than healing. A network meta-analysis ranks options; it does not prove any single one works. Still, for a repeat cycle, probiotics are reasonable to discuss with a clinician. Our guide to how to choose a probiotic covers the label basics. One option we carry is DaVinci Labs, Mega Probiotic ND 120 Capsules.

The Toothpaste Variable: SLS

Sodium lauryl sulfate, or SLS, is the foaming agent in a lot of toothpaste. It is also one of the most discussed triggers for recurrent canker sores, and one of the few you can remove in a single trip to the store.

The evidence is honest but modest. A 2019 review by Cheng found limited evidence that patients with recurrent aphthous stomatitis may benefit from SLS-free dentifrices. Limited is the right word: suggestive, not settled.

Even so, the practical advice lines up. Both the NHS and the Cleveland Clinic advise people with recurrent mouth ulcers to switch, the downside is close to zero, and unlike a rinse the change is permanent. Verdict: worth doing as a low-risk experiment.

What to Skip

Several widely shared remedy lists still name the options below. We could not find trial evidence for aphthous ulcers behind any of them, and a few rest on evidence that belongs to a different condition. Missing evidence is not proof of harm, but it is a good reason not to spend on them.

• Lysine. Lysine belongs in the cold sore conversation, where the focus is HSV-1. That evidence does not follow for an ulcer inside the mouth.
• Vitamin C. Popular for immune support, but we could not find aphthous ulcer trial evidence for it.
• Echinacea. A cold remedy, and we could not find aphthous ulcer data behind it.
• Goldenseal. A folklore antimicrobial with no aphthous ulcer trial support we could find.
• Carrot and celery juice. A persistent favorite, with no trial support we could find for ulcers inside the mouth.

The remedies that survive the evidence test tend to be the boring ones: a corrected deficiency, topical honey, topical zinc, an SLS-free toothpaste, and a salt rinse. The flashy ones tend to be borrowed from another condition or passed down untested.

When to See a Dentist or Doctor

Most canker sores are self-limiting and clear on their own. The skill is knowing when one is not routine. This section is general information, not medical advice.

1. An ulcer lasting longer than two to three weeks. Guidance disagrees here: UK sources say three weeks, US sources say two. Use three weeks as the practical line.
2. An ulcer bigger than about 1 cm. A major ulcer that size may need a clinician's care.
3. Ulcers recurring two or three or more times a year. Frequent crops are worth investigating for an underlying cause.
4. Ulcers that stop you eating or drinking. An ulcer severe enough to affect your intake needs attention.
5. A first canker sore after age 40. Getting a first one this late is unusual, so it is worth a closer look.
6. An ulcer alongside flu-like symptoms. Fever and feeling generally unwell move the question beyond a simple canker sore.

If any of these apply, see a dentist or doctor rather than self-treating further. A clinician can tell the difference between a routine canker sore and something needing specific care.

Putting It Together: What to Do This Week

Here is the order of operations, from the fastest move to the slowest.

1. Soothe and protect first. Treat the current ulcer with an evidence-backed topical, such as honey four times a day for 5 days or a topical zinc that makes contact with the ulcer. Use a salt water rinse as often as it helps, and switch to an SLS-free toothpaste now, since that change is permanent.
2. Answer the deficiency question with a blood test, not a guess. Ask for vitamin B12, folate, ferritin, and zinc. The 2015 meta-analysis found deficiencies far more common in people with recurrent ulcers, and a number beats a hunch.
3. Add the specific nutrient that has evidence, at the studied dose. If a test shows low B12, correcting it is well supported, and ask your clinician whether the sublingual 1000 mcg daily used in the 2009 trial is right for you. If recurrence is the battle, consider probiotics, which the 2022 network meta-analysis recommended as the long-term option, following the label for dose.
4. Do not expect a broad multivitamin to do the job. The 160-person trial found a once-daily multivitamin at label strength made no difference to episode count or duration. Save your budget for specific, evidence-backed moves.
5. Set a follow-up date. If ulcers keep coming two or three or more times a year, or any single ulcer passes three weeks, book the appointment instead of waiting it out.

Soothe first, because it changes how today feels. Test second, because it turns a mystery into a number. Supplement third, because that is where the evidence lives. The Agape team builds every guide around that same idea: specific, dose-level, and honest about what the evidence does and does not show.

What We Recommend

These are the nutrients this article grades, in product form, ordered from the strongest evidence signal to the most accessory option.

Frequently Asked Questions

References

1. Volkov I, Rudoy I, Freud T, et al. Effectiveness of vitamin B12 in treating recurrent aphthous stomatitis: a randomized, double-blind, placebo-controlled trial. Journal of the American Board of Family Medicine. 2009;22(1):9-16. PMID 19124628. DOI 10.3122/jabfm.2009.01.080113. https://pubmed.ncbi.nlm.nih.gov/19124628/
2. Lalla RV, Choquette LE, Feinn RS, et al. Multivitamin therapy for recurrent aphthous stomatitis: a randomized, double-masked, placebo-controlled trial. Journal of the American Dental Association. 2012;143(4):370-376. PMID 22467697. DOI 10.14219/jada.archive.2012.0179. https://pubmed.ncbi.nlm.nih.gov/22467697/
3. Chen H, Sui Q, Chen Y, Ge L, Lin M. Impact of haematologic deficiencies on recurrent aphthous ulceration: a meta-analysis. British Dental Journal. 2015;218(4):E8. PMID 25720915. DOI 10.1038/sj.bdj.2015.100. https://pubmed.ncbi.nlm.nih.gov/25720915/
4. Mousavi T, Jalali H, et al. Hematological parameters in patients with recurrent aphthous stomatitis: a systematic review and meta-analysis. BMC Oral Health. 2024. PMID 38493289. https://pubmed.ncbi.nlm.nih.gov/38493289/
5. Ghorbani A, Akbari J, Boorboor M, Nekoukar Z, Eslami G. Evaluation of zinc sulfate mucoadhesive formulation on recurrent aphthous stomatitis: a randomized double-blind, placebo-controlled clinical trial. BMC Oral Health. 2020;20(1):212. PMID 32723352. DOI 10.1186/s12903-020-01194-4. https://pubmed.ncbi.nlm.nih.gov/32723352/
6. Kim M, Kho H. Efficacy of topical application of zinc compounds for oral mucosal diseases: a systematic review and meta-analysis. Medicina Oral Patologia Oral y Cirugia Bucal. 2026;31(1):e63-e72. PMID 41273742. DOI 10.4317/medoral.27549. https://pubmed.ncbi.nlm.nih.gov/41273742/
7. El-Haddad SA, Asiri FY, Al-Qahtani HH, Al-Ghmlas AS. Efficacy of honey in comparison to topical corticosteroid for treatment of recurrent minor aphthous ulceration: a randomized, blind, controlled, parallel, double-center clinical trial. Quintessence International. 2014;45(8):691-701. PMID 25019115. DOI 10.3290/j.qi.a32241. https://pubmed.ncbi.nlm.nih.gov/25019115/
8. Liu H, Tan L, Fu G, Chen L, Tan H. Efficacy of topical intervention for recurrent aphthous stomatitis: a network meta-analysis. Medicina (Kaunas). 2022;58(6):771. PMID 35744034. DOI 10.3390/medicina58060771. https://pubmed.ncbi.nlm.nih.gov/35744034/
9. Aggour RL, Mahmoud SH, Abdelwhab A. Evaluation of the effect of probiotic lozenges in the treatment of recurrent aphthous stomatitis: a randomized, controlled clinical trial. Clinical Oral Investigations. 2021;25(4):2151-2158. PMID 32820431. DOI 10.1007/s00784-020-03527-7. https://pubmed.ncbi.nlm.nih.gov/32820431/
10. Cheng LL. Limited evidence suggests that patients with recurrent aphthous stomatitis may benefit from using sodium lauryl sulfate-free dentifrices. Journal of Evidence-Based Dental Practice. 2019;19(4):101349. PMID 31843182. DOI 10.1016/j.jebdp.2019.101349. https://pubmed.ncbi.nlm.nih.gov/31843182/
11. Das SK, Das V, Gulati AK, Singh VP. Deglycyrrhizinated liquorice in aphthous ulcers. Journal of the Association of Physicians of India. 1989;37(10):647. PMID 2632514. https://pubmed.ncbi.nlm.nih.gov/2632514/
12. Yesudian RI, Yesudian PD. Vitamins and oral mucosal diseases: from bench to the bedside. Clinics in Dermatology. 2026;44(2):281-293. PMID 41692086. DOI 10.1016/j.clindermatol.2026.02.013. https://pubmed.ncbi.nlm.nih.gov/41692086/

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.