Canker sores respond to a surprisingly wide range of treatments, from simple salt-water rinses you can make at home to prescription corticosteroid pastes and in-office laser therapy. The challenge is that no single treatment works perfectly for everyone, and what helps most depends on how severe and frequent your outbreaks are. Most minor canker sores heal on their own within one to two weeks, but the right intervention can cut pain dramatically and speed things along by several days.
Salt Water, Baking Soda, and Other Kitchen-Shelf Rinses
The simplest approach is also one of the oldest: dissolving about half a teaspoon of salt or baking soda in a cup of warm water and swishing it around the sore for 30 seconds or so, a few times a day. Neither ingredient is going to make the ulcer vanish overnight, but salt water creates a mildly hypertonic environment that draws fluid out of inflamed tissue, temporarily reducing swelling and discomfort. Baking soda does something similar while also neutralizing acids in the mouth that can irritate the raw spot. These rinses are worth trying first because they cost almost nothing, carry no real risk, and can make the wait for natural healing more bearable.
A step up from the kitchen shelf is a dilute hydrogen peroxide rinse, usually one part 3% peroxide to one part water, dabbed directly on the sore with a cotton swab or used as a brief mouth rinse. It helps clean the ulcer surface and may reduce secondary bacterial colonization. The sting on contact is real, though, and some people find it more irritating than helpful. If a simple rinse is already managing your pain, there is no reason to escalate.
Why Switching Your Toothpaste Matters
One of the most underappreciated changes you can make is checking whether your toothpaste contains sodium lauryl sulfate, the foaming agent in most commercial toothpastes. A systematic review of clinical trials found that people who switched to an SLS-free toothpaste had fewer ulcers, shorter episodes, and less pain compared to those using standard SLS-containing products.1PubMed. Effect of sodium lauryl sulfate on recurrent aphthous stomatitis: A systematic review SLS is a detergent that can strip the protective mucous layer inside your mouth, leaving the tissue more vulnerable to the small injuries that trigger canker sores. If you get canker sores more than a few times a year, switching toothpaste is one of the easiest, cheapest things to try before reaching for anything stronger.
Over-the-Counter Gels and Protective Coatings
When rinses are not enough, the pharmacy aisle offers two broad categories of relief: numbing agents and barrier-forming products.
Benzocaine gels, available at concentrations of 10% and 20%, are the most common numbing option. You dab the gel directly onto the sore, and within a minute or two, the area goes partially numb. Research on benzocaine for oral pain has found that most people can self-apply doses well below the threshold associated with methemoglobinemia, a rare but serious blood condition sometimes flagged in safety warnings.2The Journal of the American Dental Association. Benzocaine An evaluation of 10 percent and 20 percent benzocaine gels in patients with acute toothaches: Efficacy, tolerability and compliance with label dose administration directions That said, benzocaine products should not be used in children under two, and even in older children and adults, sticking to the labeled dose and frequency is important. The relief is temporary, usually fading within 20 to 30 minutes, so you may find yourself reapplying several times a day.
Barrier-forming products take a different approach: instead of numbing the nerve endings, they coat the ulcer with a protective layer that shields it from food, saliva, and friction. Hyaluronic acid gels and rinses fall into this category. A clinical study of hyaluronic acid formulations for minor canker sores found that both a mouth rinse and a topical gel promoted healing, with the gel showing a trend toward earlier improvement.3PubMed Central. Treatment of recurrent aphthous stomatitis (RAS; aphthae; canker sores) with a barrier forming mouth rinse or topical gel formulation containing hyaluronic acid: a retrospective clinical study The advantage of a barrier product is that it can reduce pain for longer stretches than a numbing gel, since the coating physically prevents contact with irritants. The downside is that the film can wash away with eating or drinking, so reapplication after meals is common.
Licorice Root Preparations
If you prefer something botanical, licorice root is one of the better-studied natural options for canker sores. A systematic review of six clinical trials covering over 300 participants found that topical licorice preparations significantly reduced ulcer pain, ulcer size, and healing time compared to placebo. By the fourth day of use, roughly four out of five people in the licorice group reported no resting pain, compared to far fewer in placebo and no-treatment groups.4PubMed Central. Topical Licorice for Aphthous: A Systematic Review of Clinical Trials The active compounds, particularly glycyrrhizin, have anti-inflammatory and antimicrobial properties that appear to calm the immune response at the ulcer site.
Licorice-based products come as dissolvable patches, gels, and mouth rinses. They are generally well tolerated when applied topically. Swallowing large amounts of glycyrrhizin over long periods can raise blood pressure, but the tiny quantities involved in a topical canker sore treatment are not a concern for most people. If you are already on blood pressure medication, mention it to your pharmacist before picking up a licorice oral product, just to be safe.
Prescription Corticosteroid Pastes
When over-the-counter products are not controlling the pain or when sores are large or unusually slow to heal, prescription-strength topical corticosteroids are usually the next step. Triamcinolone acetonide in an adhesive oral paste is one of the most widely prescribed options. It sticks to the wet tissue inside your mouth, delivering a small dose of steroid directly into the ulcer while also forming a protective barrier.
A systematic review of topical corticosteroids for canker sores found that, on average, treated ulcers healed faster and hurt less than those given placebo, though the studies used different measurement methods and the evidence on preventing future outbreaks was inconclusive.5Acta Otorrinolaringologica (English Edition). Topical Corticosteroids in Recurrent Aphthous Stomatitis. Systematic Review A comparison study pitting triamcinolone paste against curcumin gel found that triamcinolone reduced ulcer size faster, with statistically significant differences showing up within the first few days of treatment.6Journal of Indian Academy of Oral Medicine and Radiology. Correlation of Pain Score with Ulcer Size in Oral Aphthous Ulcers Using 2% Curcumin Gel and 0.1% Triamcinolone Oral Paste – A Parallel Comparison Study Formulation work has also confirmed that adhesive oral paste versions of triamcinolone acetonide deliver the drug effectively to the ulcer surface.7PubMed Central. Triamcinolone Acetonide Oromucoadhesive Paste for Treatment of Aphthous Stomatitis
Stronger corticosteroids like fluocinonide or clobetasol are sometimes prescribed for stubborn or large ulcers, though these carry a greater risk of local side effects like mucosal thinning with prolonged use. Your dentist or doctor will generally start with the mildest effective steroid and escalate only if needed. Corticosteroid rinses, where a steroid is dissolved and swished around the mouth, are useful when you have multiple sores scattered across different areas rather than a single localized ulcer.
Silver Nitrate Cautery
Chemical cautery with silver nitrate is an old technique that has survived because it does one thing well: rapid pain relief. A randomized controlled trial found that about 70% of patients treated with silver nitrate cautery experienced a significant drop in pain severity within a single day, compared to roughly 11% in the placebo group.8Oxford Academic (British Journal of Dermatology). Silver nitrate cautery in aphthous stomatitis: a randomized controlled trial The catch is that it does not speed up healing: by day seven, sores in both the treatment and placebo groups had healed at similar rates. What silver nitrate does is essentially destroy the nerve endings at the ulcer surface, so you stop feeling the sore even though the tissue still needs the same amount of time to regenerate.
The application itself stings intensely for a few seconds, and the spot turns grayish-white where the chemical contacts tissue. It is typically done in a dental or medical office. If your main complaint is excruciating pain from a sore that is making it hard to eat or talk, and you want fast relief rather than faster healing, cautery can be genuinely useful. It is not something you would do for every mild canker sore, but for the occasional severe one, it fills a niche that gels and rinses cannot.
Low-Level Laser Therapy
A growing body of evidence supports the use of low-level laser therapy, sometimes called photobiomodulation, for canker sores. This is an in-office procedure where a dental professional directs a low-power laser at the ulcer for a minute or two. Unlike surgical lasers, this does not cut or burn tissue. The light energy is thought to reduce inflammation and promote cell repair at the wound site.
In a sham-controlled study where each patient had one sore treated with an active laser and another treated with a dummy device, the actively treated ulcers healed in about three days on average, compared to roughly nine days for the sham-treated ones. Almost all patients in the active group reported complete pain relief immediately after the laser session.9PubMed Central. Efficacy of Low-Level Laser Therapy in Treatment of Recurrent Aphthous Ulcers – A Sham Controlled, Split Mouth Follow Up Study Case reports have echoed these results, describing rapid pain relief and full healing of ulcers following treatment.10PubMed Central. Low laser therapy as an effective treatment of recurrent aphtous ulcers: a clinical case reporting two locations
The downsides are practical: you need access to a provider who offers the treatment, it is not always covered by insurance, and you have to get there while the sore is still active. For people with frequent, debilitating outbreaks who have not responded well to topical treatments, it is worth asking your dentist about.
Nutritional Gaps Worth Checking
If canker sores keep coming back despite good oral hygiene and avoiding known irritants, a nutritional deficiency could be part of the picture. Research has found that people with recurrent canker sores consume less vitamin B12 and folate than the general population, and that lower blood levels of these nutrients track with more frequent outbreaks.11PubMed Central. Reduced dietary intake of vitamin B12 and folate in patients with recurrent aphthous stomatitis Changes in the mouth lining, including ulcer-like sores, can be among the earliest signs of B12 or folate deficiency, sometimes appearing before other symptoms like fatigue or tingling in the hands.
Iron and zinc deficiencies have also been linked to recurrent canker sores in some studies. The practical takeaway is that if you deal with frequent outbreaks, a simple blood panel checking B12, folate, iron, and zinc can be informative. If a deficiency shows up, correcting it through diet or supplementation may reduce how often sores appear. This is not a guaranteed fix, since many people with normal nutrient levels still get canker sores, but it is a relatively easy box to check.
Triggers That Keep Canker Sores Coming Back
Treatment is only half the equation. Understanding what sets off your outbreaks can do as much for your quality of life as any gel or prescription. The known triggers span a surprisingly wide range.
Stress is one of the most commonly reported triggers, and the connection is more than anecdotal. Research has shown that people experiencing psychological stress have elevated salivary cortisol and shifts in immune activity that can promote the inflammatory response underlying canker sores.12PubMed Central. Relationship of salivary cortisol and anxiety in recurrent aphthous stomatitis Stress does not cause ulcers directly, but it appears to lower the threshold at which the immune system overreacts to minor injuries inside the mouth.
Dietary sensitivities are another major trigger category. Some people react to specific weak organic acids found in common foods. A clinical study demonstrated that citric acid, found in citrus fruits and many soft drinks, could reproducibly trigger canker sores in a sensitive patient when applied to the oral lining, while the same application had no effect on controls. Acetic acid, the main acid in vinegar, provoked similar reactions.13Journal of Allergy. Canker sores from allergy to weak organic acids (citric and acetic): Case report and clinical study Avoiding the offending foods led to a marked improvement. If you notice that outbreaks cluster after eating certain foods, keeping a simple food diary for a few weeks can help identify your personal triggers. Common culprits beyond citrus include tomatoes, chocolate, coffee, nuts, and spicy foods, though the list varies widely from person to person.
Mechanical injury is easy to overlook but worth paying attention to. Biting the inside of your cheek, brushing too aggressively, or irritation from braces or a rough dental restoration can set off an ulcer in someone predisposed. The combination of local tissue damage and an immune system primed to overreact is often what tips a minor mouth injury into a full canker sore. Broader immune and hormonal factors, including gastrointestinal conditions like celiac disease and Crohn’s disease, can also drive recurrent outbreaks.14Springer Link. Etiopathogenesis of recurrent aphthous stomatitis and the role of immunologic aspects: literature review
The Oral Microbiome Connection
Research into the bacteria living inside the mouth has added another layer to the canker sore story. A study comparing the oral microbiomes of people with recurrent canker sores to healthy controls found clear differences: people with canker sores had significantly higher levels of certain bacteria in the Proteobacteria group and lower levels of Firmicutes, a phylum generally associated with a healthy oral environment.15PubMed Central. Altered oral microbiota composition associated with recurrent aphthous stomatitis in young females Whether these bacterial shifts are a cause of canker sores, a consequence of the inflamed environment, or both, is still being worked out.
What this means practically is still limited. There are no proven probiotic treatments specifically for canker sore prevention yet. But the finding does suggest that the overall health of your mouth’s microbial community matters, and that harsh products or habits that disrupt that community, like alcohol-based mouthwashes used excessively, might not be helping. Gentle oral care that supports a balanced microbiome is consistent with both the SLS-free toothpaste evidence and the broader emerging picture of what keeps the mouth’s immune defenses functioning well.
When Canker Sores Signal Something Bigger
Most canker sores are annoying but harmless. There are situations, though, where they warrant a closer look. An ulcer that lasts longer than three weeks, sores that grow unusually large (bigger than about a centimeter across), outbreaks accompanied by fever or severe fatigue, or sores that start appearing in new locations like the genitals should all prompt a visit to a doctor or dentist.
Recurrent canker sores can be an early or prominent feature of several systemic conditions, including celiac disease, inflammatory bowel disease, and Behçet’s disease. The etiology review literature describes how gastrointestinal disorders, hormonal shifts, and immune dysregulation can all manifest as mouth ulcers.14Springer Link. Etiopathogenesis of recurrent aphthous stomatitis and the role of immunologic aspects: literature review In some cases, treating the underlying condition resolves the mouth sores entirely. A blood test for celiac antibodies or screening for nutrient malabsorption can sometimes connect the dots between persistent mouth ulcers and a condition that was otherwise flying under the radar.
Certain medications can also cause mouth ulcers that look identical to canker sores. Methotrexate, some blood pressure drugs, and nonsteroidal anti-inflammatory medications are among the more common offenders. If your sores started or worsened after beginning a new medication, bring it up with your prescriber rather than assuming it is just bad luck.