Baking soda is generally safe to use on a canker sore, either as a paste applied directly or dissolved in water as a mouth rinse. It has documented antibacterial properties and can shift the pH of your mouth in ways that make the environment less hospitable to the bacteria that aggravate open sores. That said, baking soda is not a proven cure for canker sores, and what it actually does for them is more modest than many home-remedy guides suggest. The real picture involves understanding what baking soda can and cannot accomplish, how to use it without irritating things further, and when frequent canker sores point to something else entirely.
What Baking Soda Actually Does in Your Mouth
Sodium bicarbonate, the chemical name for baking soda, is mildly alkaline. When you dissolve it in water and swish it around, it raises your mouth’s pH. That shift matters because oral bacteria thrive in acidic environments. A prospective study found that using a sodium bicarbonate rinse led to a decrease in bacterial colony counts, with reductions seen in common oral bacteria like Viridans Streptococci and Moraxella species.1PubMed Central. The effect of sodium bicarbonate oral rinse on salivary pH and oral microflora: A prospective cohort study Fewer bacteria around an open sore means less chance of secondary infection and potentially less pain, since bacterial byproducts can irritate exposed tissue.
A canker sore (aphthous ulcer) is already an immune-mediated wound on the mucous membrane of your mouth. Your body created it, not an infection. But once the surface breaks down, bacteria in your mouth can colonize the raw area and make things worse. Baking soda does not address the root cause of why the ulcer formed. What it does is clean up the neighborhood around the wound, which can reduce discomfort and may support the body’s own healing process.
There is also some evidence from research on chemotherapy-induced mouth sores, called oral mucositis, that sodium bicarbonate mouthwash can help. In one study of cancer patients, a sodium bicarbonate rinse significantly reduced the severity of oral mucositis and lowered the number of patients still affected after treatment.2Tabari Biomedical Student Research Journal. Comparative Evaluation of the Efficacy of Ice Cubes Versus Sodium Bicarbonate Mouthwash both as Prophylactic Measure and as Treatment of Oral Mucositis Induced by Systemic Anticancer Therapies Oral mucositis is not the same thing as a standard canker sore, but both involve painful ulceration of the mouth’s soft tissue, so the finding is at least suggestive that baking soda rinses can help oral wounds heal.
How to Use It Safely
There are two common ways to use baking soda for canker sores, and both are considered safe for most people. A dental review described baking soda as having minimal abrasivity and being virtually free of side effects when used as a mouthwash or oral-care adjunct.3PubMed. Sodium bicarbonate: A review and its uses in dentistry
- Rinse: Dissolve about a teaspoon of baking soda in half a cup of warm water. Swish gently for 15 to 30 seconds, making sure the rinse reaches the sore, then spit it out. You can repeat this several times a day, especially after meals.
- Paste: Mix a small amount of baking soda with a few drops of water to form a thick paste. Dab it directly onto the sore with a clean finger or cotton swab. Leave it on for a minute or two, then rinse your mouth with plain water.
The paste method puts a more concentrated dose of baking soda directly on the ulcer, which some people find stings at first. That brief burning sensation is normal and fades quickly. If the pain is sharp or prolonged, stick with the diluted rinse instead. Children may find the taste and sting unpleasant enough that the rinse is the better option for them.
One thing to avoid: do not scrub the sore with a baking soda paste or use it as an abrasive. The point is gentle contact, not mechanical action. The surface of a canker sore is already raw, and scrubbing will break down healing tissue and make it hurt more. Also, while baking soda is safe for occasional oral use, swallowing large amounts can upset your stomach or cause electrolyte shifts. Rinsing and spitting is the way to go.
What Baking Soda Will Not Do
The honest limitation is that no high-quality clinical trial has tested baking soda specifically as a treatment for aphthous ulcers and demonstrated that it speeds up healing time. Most canker sores resolve on their own in one to two weeks. Baking soda may make the sore less painful and keep the area cleaner while your body does the actual repair work, but expecting it to cut healing time in half would be getting ahead of the evidence.
If you see home-remedy lists that promise baking soda will “cure” canker sores overnight, that is marketing language, not science. The antibacterial and pH-shifting properties are real, but they are supportive, not curative. Think of it like keeping a scraped knee clean: the bandage and antiseptic are helpful, but your immune system is the one closing the wound.
Honey as an Alternative With Stronger Evidence
If you are looking for a home remedy with direct clinical evidence behind it for canker sores specifically, honey has a more established track record. A randomized controlled trial compared topical honey to a topical corticosteroid and to a placebo for treating minor aphthous ulcers. The honey group showed a statistically significant reduction in ulcer size, days of pain, and degree of redness compared to the other groups, and no side effects were reported.4PubMed. Efficacy of honey in comparison to topical corticosteroid for treatment of recurrent minor aphthous ulceration: a randomized, blind, controlled, parallel, double-center clinical trial
That is a notable result because the comparison was not just honey versus doing nothing. Honey held its own against a corticosteroid, which is the standard clinical treatment for canker sores. Raw, unprocessed honey applied directly to the ulcer several times a day appears to be both effective and safe. Some people combine approaches, using a baking soda rinse to clean the area and then applying honey afterward. There is no clinical trial testing that specific combination, but since both are safe individually, the logic of pairing an antibacterial rinse with an anti-inflammatory topical is reasonable.
Your Toothpaste Might Be Making Things Worse
One of the most actionable findings in canker sore research has nothing to do with treatments and everything to do with prevention. Sodium lauryl sulfate, commonly abbreviated SLS, is a foaming agent found in most conventional toothpastes. A systematic review of the evidence found that switching to an SLS-free toothpaste significantly reduced the number of ulcers, the duration of each ulcer, the number of episodes, and ulcer pain in people who get recurrent canker sores.5PubMed. Effect of sodium lauryl sulfate on recurrent aphthous stomatitis: A systematic review
A separate randomized controlled trial found that while SLS-free toothpaste did not significantly reduce the number of ulcers or episodes on its own, it did improve the healing process and reduce day-to-day pain.6PubMed. Effect of sodium lauryl sulfate on recurrent aphthous stomatitis: a randomized controlled clinical trial The two findings are not contradictory; the systematic review pooled multiple studies and found broader benefits, while the single trial found a more modest effect focused on pain and healing speed. Either way, the direction is consistent: SLS irritates the oral mucosa, and removing it helps.
If you get canker sores frequently, switching your toothpaste is one of the simplest changes you can make. SLS-free options are widely available, often marketed for sensitive mouths. You do not need a prescription or special formulation. Read the ingredient list on your current toothpaste; if sodium lauryl sulfate is listed, try one without it for a few months and see whether your outbreaks change.
The Stress Connection
Many people notice that canker sores seem to flare up during stressful periods, and the research supports this observation. A study examining the relationship between psychological stress and recurrent aphthous stomatitis concluded that stress may act as a trigger or a modifying factor, though it is not considered a direct cause of the disease.7PubMed Central. Psychological stress and recurrent aphthous stomatitis The distinction matters: stress does not create canker sores out of nothing, but in someone who is already predisposed, it can tip the balance.
Research measuring stress hormones in people with active canker sores found that salivary cortisol and DHEA levels were significantly elevated compared to healthy controls.8PubMed Central. Salivary cortisol and dehydroepiandrosterone as oral biomarkers to determine stress in patients with recurrent aphthous stomatitis Cortisol suppresses parts of the immune response while ramping up inflammation, which creates the kind of environment where the immune system may mistakenly attack the mouth’s own tissue. If you are someone whose canker sores seem to cluster around exam weeks, work deadlines, or emotionally difficult periods, the pattern is likely real, not imagined.
This does not mean you can meditate your way out of canker sores. But stress management sits alongside toothpaste choice and nutritional status as one of the modifiable factors worth paying attention to if you are trying to reduce how often they appear.
When Frequent Canker Sores Signal Something Else
Getting a canker sore once or twice a year is unremarkable. Getting them constantly, or in clusters, or in an unusual pattern can be a sign of an underlying condition that no amount of baking soda will address.
Iron deficiency is one of the more common nutritional links. A study of patients with recurrent aphthous stomatitis found a significant association with iron deficiency.9Pakistan BioMedical Journal. Importance Of Iron Deficiency in Patients with Recurrent Aphthous Stomatitis Iron plays a role in maintaining healthy mucous membranes, and when levels are low, the tissue lining your mouth becomes more fragile and more prone to ulceration. Deficiencies in B vitamins, zinc, and folate have also been implicated, though the strength of the evidence varies by nutrient. If you are getting frequent canker sores and also feeling unusually fatigued, a blood test to check your iron and B12 levels is worth requesting.
Celiac disease is another condition where the mouth can be the first clue. Recurrent canker sores are recognized as an oral manifestation of celiac disease, sometimes showing up before the classic digestive symptoms do. Inflammatory bowel diseases like Crohn’s disease and ulcerative colitis also carry a higher rate of canker sores, likely because of both the inflammatory disease process itself and the nutritional deficiencies caused by chronic intestinal inflammation.10PubMed Central. Can You Put Baking Soda on a Canker Sore? – Section: When the Gut Is the Real Problem A person who gets frequent, stubborn canker sores along with bloating, chronic diarrhea, or unexplained weight loss should bring those symptoms up with a doctor. The canker sores may be a surface-level expression of a treatable gut condition.
Behçet’s disease, certain autoimmune disorders, and immunodeficiency states can also present with recurrent oral ulcers. These are less common but worth mentioning because people sometimes spend years treating the symptom with rinses and gels when the underlying condition deserves its own diagnosis and management.
Prescription and Over-the-Counter Alternatives
When baking soda or honey is not cutting it, there are stronger options. Over-the-counter products containing benzocaine or a similar topical anesthetic can numb the sore and make eating tolerable. These do not speed healing but provide immediate pain relief. Oral gels with a protective coating, like those based on hyaluronic acid, form a barrier over the ulcer that shields it from food and saliva, which can reduce pain and may promote faster healing.
For more severe or frequent canker sores, doctors may prescribe topical corticosteroids, typically in the form of a gel or paste applied directly to the ulcer. These reduce the localized immune response that is driving the ulceration and can significantly shorten healing time. Prescription-strength mouthwashes containing dexamethasone or other anti-inflammatory agents are another option for people with multiple simultaneous sores.
In rare cases where canker sores are large, persistent, or resistant to topical treatment, systemic medications like colchicine or thalidomide have been used, though these come with more significant side effects and are reserved for severe disease. The vast majority of people will never need anything beyond topical care and lifestyle adjustments.
Canker Sores Versus Cold Sores
This distinction comes up constantly and is worth clarifying because people sometimes apply treatments meant for one condition to the other. Canker sores (aphthous ulcers) appear inside the mouth, on the soft tissue of the cheeks, the base of the gums, or the underside of the tongue. They are not caused by a virus and are not contagious. Cold sores (fever blisters) appear on or around the lips, are caused by herpes simplex virus, and are contagious.
Baking soda rinses are fine for canker sores, as discussed. For cold sores, the standard treatments are antiviral medications like acyclovir or valacyclovir, and baking soda is not going to accomplish anything meaningful. If you are unsure which type of sore you have, the location is usually the biggest clue: inside the mouth and on soft tissue is likely a canker sore; on the lip or surrounding skin, especially with a tingling prodrome and a blister-like appearance, is likely a cold sore. Sores that appear on the hard palate or gums near the gum line can occasionally be ambiguous, and a dentist can help with identification.
One practical implication of the distinction: if you have been putting baking soda on what you think is a canker sore on your lip, and it is actually a cold sore, you are not treating the underlying viral infection. Starting an antiviral within the first day or two of a cold sore outbreak can shorten the episode meaningfully, so correct identification matters.