Canker sores have no cure. Here is what the evidence says actually helps

The most useful thing to know about canker sores is that no treatment reliably cures or prevents them, and the ulcers clear on their own — so the honest goal of any remedy is to ease the pain and perhaps shorten an episode, not to make the problem go away [s1]. A Cochrane review of pills and other systemic treatments found no single one effective and insufficient evidence to support or refute any of them [s1]. A later network meta-analysis of topical treatments found that a handful may modestly help, but the trials underneath that conclusion are small and weak [s2]. Almost everything sold for canker sores sits on that thin evidence base.

A common problem with an unglamorous truth

Recurrent aphthous stomatitis — canker sores — is the most frequent form of mouth ulceration, striking otherwise healthy people in repeated episodes that can make eating and drinking genuinely painful [s1]. Because the sores recur and then resolve, treatment has never been aimed at a cure. As the Cochrane review puts it, the point of treatment is pain relief and the promotion of healing, to reduce how long an episode lasts or how often it comes back [s1]. That framing is the antidote to most of the marketing: a product that promises to clear a canker sore is promising something the sore was going to do anyway.

Systemic drugs: no winner

The Cochrane review looked specifically at systemic interventions — treatments taken by mouth or otherwise acting body-wide rather than dabbed on the ulcer. It pooled 25 trials, 22 of them placebo-controlled and eight making head-to-head comparisons, covering 21 different interventions [s1]. Only one of those trials was judged to be at low risk of bias [s1]. The verdict was that no single treatment was effective and the results remained inconclusive about the best systemic option [s1]. The reviewers were careful to say what that does and does not mean: the failure likely reflects the poor quality and small number of the trials rather than proof that the drugs do nothing, and in practice individual drugs seem to work for individual patients [s1]. Systemic treatment is also generally reserved for people whose ulcers have not responded to topical measures first [s1].

Topical treatments: a messy signal

Most people reach for something applied directly to the sore — a gel, a rinse, a paste — and a 2022 network meta-analysis gathered that evidence in one place: 72 trials, 5,272 subjects, and 29 different topical interventions [s2]. This is where a modest signal appears. The analysis ranked honey, an insulin liposome gel, laser treatment, amlexanox, glycyrrhiza (liquorice), and the corticosteroid triamcinolone among the better performers on healing, while probiotics and the antiseptic rinse chlorhexidine appeared to lengthen the gap between ulcers and reduce recurrence [s2]. On the other side, doxycycline and penicillin carried a high risk of adverse events [s2]. The authors' bottom line was to consider laser as a short-term measure during a flare and probiotics as a longer-term one [s2].

Those rankings should be read with the same caution the systemic review demands. A network meta-analysis stitches together many small, uneven trials and infers comparisons that were often never tested directly, so "better performer" here means better within a weak and heterogeneous evidence base, not proven superiority. What survives the caution is a practical shape: a topical corticosteroid such as triamcinolone and an antiseptic mouthwash such as chlorhexidine are among the more studied options for pain and recurrence, while the exotic-sounding entries rest on a thinner footing still.

What holds up, and when to see someone

The defensible summary is that canker sores heal without treatment, no product cures or prevents them, and the best that topical measures offer is some relief and possibly a slightly shorter or less frequent episode — on evidence that is real but low-quality [s1] [s2]. Anything promising more than that is overselling what the trials show.

The reviews studied recurrent ulceration in otherwise healthy people [s1], which is also the clue to when a mouth ulcer is worth a clinician's attention: a sore that fails to heal, is unusually large, keeps recurring in a way that disrupts eating, or comes with other symptoms falls outside that ordinary picture, because mouth ulcers have many causes beyond canker sores. Which treatment suits a given person, and whether an ulcer is a simple canker sore at all, is a clinical judgement this article does not make.