Natural Management of Canker Sores

Evidence-based natural approaches to recurrent aphthous stomatitis (canker sores), including sublingual vitamin B12, zinc, deglycyrrhizinated licorice, and probiotics — backed by randomized trials and systematic reviews

Canker sores — small, shallow ulcers that form on the soft tissues inside the mouth — affect roughly 20% of people at some point in their lives, making them the most common oral mucosal condition. They heal on their own within one to two weeks, but the pain can make eating, drinking, and speaking genuinely miserable. For people who get them repeatedly (a pattern called recurrent aphthous stomatitis, or RAS), the burden adds up over months and years. The most consistently effective natural intervention is sublingual vitamin B12: a randomized trial showed that taking 1000 mcg under the tongue daily for six months led to 74% of participants becoming completely free of ulcers, compared with 32% in the placebo group — and the benefit appeared regardless of whether people were deficient in B12 to begin with [1]. Zinc and a specialized form of licorice root (deglycyrrhizinated licorice, or DGL) round out the evidence-backed options [3][5].

Vitamin B12: The Strongest Evidence

Sublingual vitamin B12 is the most thoroughly studied natural treatment for recurrent canker sores, and the results are striking. The key trial gave participants 1000 mcg of cyanocobalamin dissolved under the tongue daily for six months. By months five and six, the treatment group had significantly shorter outbreak durations, fewer ulcers per episode, and less pain than the placebo group [1]. Most remarkably, the benefit appeared in people with perfectly normal serum B12 levels — suggesting the mechanism isn't simply correcting a nutritional deficiency but involves a direct effect on mucosal healing or immune regulation in oral tissue.

Sublingual delivery (letting the tablet dissolve under the tongue rather than swallowing it) is thought to achieve higher local concentrations in the oral mucosa than oral supplementation. Standard over-the-counter sublingual B12 tablets at 1000 mcg are inexpensive and well tolerated. A separate RCT confirmed that B12 applied as an ointment directly to an ulcer significantly reduced pain within two days compared to placebo, with the treatment group achieving a mean pain score of 0.36 versus 1.80 in controls [2]. Together, these trials support both a long-term preventive role (sublingual daily supplementation) and a short-term symptomatic role (topical B12) for this vitamin.

Zinc: Addressing a Common Deficiency

Serum zinc levels are consistently lower in people with recurrent aphthous stomatitis compared to healthy controls — a finding confirmed across multiple studies worldwide. Zinc plays important roles in mucosal integrity, wound healing, and immune cell activity, all of which are relevant to canker sore formation and recovery.

A 2021 systematic review of seven clinical trials in 482 RAS patients found that five of the seven studies showed significantly better outcomes with zinc supplementation compared to controls, particularly for reducing recurrence rates [3]. Three of four studies examining symptoms (ulcer size, pain, healing time) also found meaningful improvements favoring zinc. Results were more consistent for topical zinc formulations — such as mucoadhesive zinc tablets that adhere directly to the ulcer — than for swallowed systemic zinc sulfate. If you get frequent canker sores, having your zinc levels checked and supplementing if low (typically 15–30 mg zinc daily with food) is a reasonable first step, and topical zinc preparations may provide additional symptomatic benefit when ulcers occur.

Deglycyrrhizinated Licorice (DGL) Mouthwash

Licorice root contains glycyrrhizinic acid, a compound with potent anti-inflammatory and mucosal-healing properties. Deglycyrrhizinated licorice (DGL) removes the glycyrrhizin component that can raise blood pressure with long-term use, leaving behind compounds that support mucosal healing without that risk.

In an early clinical study, 20 patients with aphthous ulcers used a DGL mouthwash (200 mg DGL powder dissolved in 200 mL warm water) four times daily [5]. Fifteen of the 20 patients — 75% — experienced 50–75% improvement within a single day, and most had complete healing by the third day. While the study was small and uncontrolled, the rapid and consistent response is notable. DGL mouthwash is easy to prepare using commercially available DGL powder or chewable tablets dissolved in water. It carries essentially no risk and can be used at the first sign of a sore to reduce pain and duration.

Probiotics: Modest Pain Relief

The gut microbiome and oral microbiome are connected, and the same beneficial bacteria that support gut health also populate the mouth. A 2020 systematic review and meta-analysis of seven randomized controlled trials found that probiotics produced a statistically significant reduction in oral pain from canker sores (mean difference -1.72, P = 0.0001) compared to placebo [4]. However, probiotics alone were less effective at reducing ulcer severity or size. The clearest benefit was for pain management, and greater effects were seen when probiotics were combined with other treatments.

Fermented foods — kefir, yogurt with live cultures, sauerkraut, kimchi — provide diverse lactobacillus and bifidobacterium strains. Dedicated oral-specific probiotic lozenges that dissolve in the mouth may be more directly effective for oral mucosal support than swallowed capsules, though strain-specific evidence is still emerging. See our kefir page for more on fermented food choices.

Avoiding Common Triggers

Identifying and reducing personal triggers can significantly decrease recurrence frequency, even without any supplementation:

Sodium lauryl sulfate (SLS) in toothpaste: This harsh detergent disrupts the protective mucin layer in the mouth and is a well-recognized trigger for many people. Switching to an SLS-free toothpaste is a simple, cost-free change worth trying.
Physical trauma: Biting the inside of your cheek, hard or sharp foods (chips, crusty bread), and ill-fitting dental appliances can initiate ulcers in susceptible people. A soft-bristled toothbrush and eating more carefully during flare-prone periods helps.
Stress: Psychological stress is one of the most consistently reported triggers for RAS flares. Stress management practices — sleep, exercise, breathwork — may reduce recurrence frequency over time.
Certain foods: Acidic foods (citrus, tomatoes, vinegar), and some people react to gluten or to foods high in arginine (nuts, chocolate). Keeping a diary to identify personal patterns is useful.
Nutritional deficiencies: Beyond B12 and zinc, deficiencies in folate, iron, and vitamin B6 have all been associated with increased aphthous stomatitis frequency. A blood test panel for these nutrients is worth doing if canker sores are frequent.

Practical Protocol

For someone getting canker sores more than two or three times a year, a reasonable starting approach is:

Switch to an SLS-free toothpaste
Start sublingual vitamin B12 1000 mcg daily (at least three to six months to judge effect)
Have zinc and B12 levels checked; supplement zinc to low-normal range if deficient
At the first sign of a sore, dissolve DGL in warm water and rinse for two minutes, four times daily
Add a probiotic food or lozenge daily for general mucosal support

Evidence Review

Sublingual Vitamin B12: The Primary RCT

Volkov et al. 2009 (PMID 19124628) conducted a randomized, double-blind, placebo-controlled trial across primary care clinics. Fifty-eight adults with recurrent aphthous stomatitis (mean of 2.6 episodes per month at baseline) were randomized to sublingual cyanocobalamin 1000 mcg daily or matching placebo for six months. Primary outcomes included duration of outbreaks, number of ulcers, and pain intensity. Secondary outcome was the proportion reaching "no aphthous ulcers status" in the final treatment month. By months 5–6, the B12 group showed statistically significant improvements in all three primary outcomes compared to placebo. Crucially, 74.1% of the B12 group versus 32.0% of the placebo group were free of ulcers during the final month (P < 0.01). A critical finding: the benefit was observed in participants with both normal and low serum B12 levels, indicating the mechanism extends beyond simple deficiency correction. The authors hypothesized direct effects on oral mucosal immune regulation or epithelial repair capacity. The study's strength is its robust double-blind placebo-controlled design with a large effect size and clear dose-response trajectory over six months.

Liu and Chiu 2015 (PMID 26025792) tested topical vitamin B12 for acute pain relief in a double-blind, placebo-controlled RCT at a Taiwan nursing home. Forty-two patients with active aphthous ulcers were randomized to vitamin B12 ointment or placebo ointment applied to the ulcer twice daily for two days. The primary outcome was pain on a numeric scale. The B12 group achieved a mean pain score of 0.36 versus 1.80 in the placebo group (P < 0.001), representing a clinically meaningful and statistically robust pain reduction within just two days of treatment. This trial complements the Volkov trial: it confirms that B12 works locally at the site of ulceration, not only systemically, and supports the use of topical B12 preparations for rapid acute pain management alongside longer-term oral supplementation for prevention.

Zinc Supplementation: Systematic Review

Halboub et al. 2021 (PMID 34146924) conducted a systematic review of seven clinical trials enrolling 482 patients with recurrent aphthous stomatitis. The included studies tested various zinc preparations: topical mucoadhesive zinc sulfate tablets, systemic oral zinc sulfate, and zinc-containing multivitamins. Five of the seven studies found significantly better outcomes with zinc compared to control conditions for reducing recurrence rates; two studies found no significant difference. For symptom management (ulcer size, healing time, pain), three of four studies reported meaningful improvements favoring zinc. The review authors noted that topical zinc formulations showed more consistent efficacy than systemic preparations — possibly because local concentration at the mucosal surface is more relevant than systemic zinc levels for this condition. A pooled analysis across observational studies confirmed that serum zinc levels are significantly and consistently lower in RAS patients compared to healthy controls, providing biological plausibility for supplementation. The review is limited by heterogeneity in zinc formulations, doses, and outcome measures across included trials, making a formal meta-analysis difficult. However, the weight of evidence supports zinc supplementation — particularly topical forms — as a useful adjunct for RAS management.

Probiotics: Meta-Analysis of Seven RCTs

Cheng et al. 2020 (PMID 33273680) performed a systematic review and meta-analysis of seven randomized controlled trials assessing probiotics for recurrent aphthous stomatitis. Various probiotic products were tested across trials (predominantly Lactobacillus-based strains, some as lozenges, some as capsules). The primary meta-analysis showed a significant reduction in oral pain with probiotics versus placebo: standardized mean difference of -1.72 (P = 0.0001). However, probiotics alone did not significantly reduce ulcer severity (size and extent of lesions). Subgroup analyses found that combining probiotics with other treatments — corticosteroids or antiseptic gels — produced superior outcomes compared to those treatments alone, suggesting probiotics enhance rather than replace established therapies. The meta-analysis is limited by substantial heterogeneity in probiotic strains, formulations, and trial designs, which complicates interpretation. Nevertheless, the pain-reduction signal is statistically robust and clinically plausible: probiotic bacteria influence local immune regulation and inflammatory cytokine production in mucosal tissue, potentially modulating the painful inflammatory response without necessarily accelerating epithelial closure.

DGL Mouthwash: Early Clinical Evidence

Das et al. 1989 (PMID 2632514) reported on 20 patients with aphthous ulcers who used a mouthwash of 200 mg deglycyrrhizinated licorice powder dissolved in 200 mL warm water, applied four times daily for up to two weeks. Fifteen of 20 patients (75%) experienced 50–75% improvement within one day of starting treatment, with complete healing of ulcers by the third day in most cases. This is a small, open-label study without a control arm, so it cannot establish causality with certainty. However, the rapid, consistent response in the majority of patients and the well-characterized pharmacology of DGL compounds (anti-inflammatory, mucoadhesive, mucoprotective via enhanced prostaglandin-mediated mucus secretion) support biological plausibility. Glycyrrhizin-free licorice preparations are safe for topical use and carry essentially no risk of the blood pressure elevation associated with whole licorice consumed in large quantities. The study's limitation is its age and methodological simplicity — a randomized controlled trial of DGL for RAS has not, to date, been conducted. The evidence quality is modest, but the safety profile and mechanistic plausibility make DGL mouthwash a reasonable low-risk adjunct, especially for the acute pain and duration of individual ulcers.

Evidence Summary

Sublingual vitamin B12 supplementation has the strongest and most methodologically rigorous evidence for preventing recurrent aphthous stomatitis, with a large effect size in a properly conducted RCT and an additional RCT confirming acute pain relief with topical B12. Zinc supplementation has a well-established biological rationale (consistent zinc deficiency in RAS patients) and a majority of clinical trials showing benefit, particularly with topical formulations. Probiotics demonstrate modest but statistically reliable pain reduction in meta-analysis of seven RCTs. DGL mouthwash has the weakest evidence by trial quality but compelling early clinical results and an excellent safety profile, making it a reasonable practical addition. Avoiding sodium lauryl sulfate in toothpaste lacks large RCT evidence but is supported by mechanistic data and widely reported anecdotally. Together, these approaches offer a meaningful non-pharmaceutical toolkit for reducing both the frequency and severity of recurrent canker sores.

References

Effectiveness of vitamin B12 in treating recurrent aphthous stomatitis: a randomized, double-blind, placebo-controlled trialVolkov I, Rudoy I, Freud T, Sardal G, Naimer S, Peleg R, Press Y. Journal of the American Board of Family Medicine, 2009. PubMed 19124628 →
The Effectiveness of Vitamin B12 for Relieving Pain in Aphthous Ulcers: A Randomized, Double-blind, Placebo-controlled TrialLiu HL, Chiu SC. Pain Management Nursing, 2015. PubMed 26025792 →
Zinc supplementation for prevention and management of recurrent aphthous stomatitis: a systematic reviewHalboub E, Al-Maweri SA, Parveen S, Al-Wesabi M, Al-Sharani HM, Al-Sharani A, Al-Kamel A, Albashari A, Shamala A. Journal of Trace Elements in Medicine and Biology, 2021. PubMed 34146924 →
The efficacy of probiotics in management of recurrent aphthous stomatitis: a systematic review and meta-analysisCheng B, Zeng X, Liu S, Zou J, Wang Y. Scientific Reports, 2020. PubMed 33273680 →
Deglycyrrhizinated liquorice in aphthous ulcersDas SK, Das V, Gulati AK, Singh VP. Journal of the Association of Physicians of India, 1989. PubMed 2632514 →