Most canker sores heal on their own within 10 to 14 days, but the right combination of pain relief and oral care can cut down on discomfort and speed things along. These small, round sores appear inside the mouth and are not contagious, unlike cold sores, which form on the outside of the lips. Here’s what actually works to treat them and keep them from coming back.
Make Sure It’s a Canker Sore
Canker sores show up inside your mouth, on the inner cheeks, gums, tongue, or soft palate. They’re typically a single round white or yellow sore surrounded by a red border. Cold sores (fever blisters) are a different thing entirely: clusters of small, fluid-filled blisters that form on the outside of the mouth, usually along the lip border. Cold sores are caused by a virus and require antiviral treatment, so the distinction matters before you start treating anything.
Home Remedies That Help
A saltwater or baking soda rinse is the simplest and most reliable home treatment. Mix 1 teaspoon of table salt and 1 teaspoon of baking soda into 4 cups of warm water. Swish about a tablespoon of the solution around your mouth for 15 to 30 seconds, then spit it out. Repeat every four to six hours. This keeps the area clean and creates an environment that helps the sore heal faster.
While the sore is active, avoid spicy, acidic, or rough-textured foods that scrape against it. Citrus fruits, tomato sauce, chips, and crusty bread are common irritants. Sticking with softer, blander foods for a week or so makes a real difference in how much pain you deal with day to day.
Applying a small amount of milk of magnesia directly to the sore with a cotton swab can also coat and soothe it. Some people find that holding a damp tea bag against the sore helps, though this is more about comfort than proven healing speed.
Over-the-Counter Products
If a rinse isn’t enough, look for OTC gels, pastes, or liquids with benzocaine as the active ingredient. Benzocaine is a topical numbing agent that temporarily blocks pain at the sore site. Products like Anbesol, Orabase, and Zilactin-B all contain it. Apply directly to the sore as soon as you notice it forming for the best results.
Hydrogen peroxide rinses designed for mouth sores (such as Orajel Antiseptic Mouth Sore Rinse) are another option. These work by cleaning the ulcer and reducing bacteria around it. Don’t use regular household hydrogen peroxide at full strength. Stick with products formulated for oral use.
When Canker Sores Need Stronger Treatment
Minor canker sores, the most common type, heal in about two weeks. Major canker sores can last up to a month and are noticeably larger and deeper. A third type, called herpetiform ulcers, appears as clusters of tiny sores that can merge together and persist for anywhere from 10 to 100 days. These can make eating and speaking extremely difficult.
For severe or recurring sores, a dentist or doctor can prescribe a steroid-based mouth rinse that reduces inflammation directly at the ulcer. These rinses are swished and spit out several times a day, typically after meals and before bed. They work faster than OTC options for stubborn or large sores. If you get canker sores two or three times a year, they last longer than two weeks, are larger than a centimeter (roughly the size of a pea), or come with fever and flu-like symptoms, it’s worth getting them evaluated.
Nutrient Deficiencies and Recurring Sores
If canker sores keep coming back, the cause may be nutritional. Deficiencies in vitamin B12, folic acid, iron, and other B vitamins (B1, B2, and B6) have all been linked to recurrent outbreaks. In one clinical trial, patients who took a daily sublingual B12 supplement for six months saw dramatic improvement: 74 percent were completely free of ulcers after six months, compared to 32 percent in the placebo group. Correcting a deficiency in B12 or folic acid through supplementation can sometimes stop the cycle entirely.
If you suspect a deficiency, a simple blood test can confirm it. This is especially worth considering if you follow a vegetarian or vegan diet, since B12 is found almost exclusively in animal products, or if your diet is low in leafy greens and legumes, which are primary sources of folate.
Preventing Future Outbreaks
One overlooked trigger is sodium lauryl sulfate (SLS), a foaming agent found in most toothpastes. SLS can irritate the lining of your mouth and may contribute to canker sore formation in people who are prone to them. Switching to an SLS-free toothpaste is a low-effort change that some people find makes a noticeable difference in how often sores appear. Brands like Sensodyne, Biotene, and certain varieties of Tom’s of Maine offer SLS-free options.
Other common triggers include accidental bites to the inside of the cheek, aggressive tooth brushing with a hard-bristled brush, stress, hormonal changes, and food sensitivities. Keeping a rough log of when sores appear can help you identify your personal triggers. Some people notice patterns around certain foods (nuts, chocolate, strawberries, and cheese are frequent culprits), while others see flare-ups during high-stress periods or after dental work that irritates the mouth.
Using a soft-bristled toothbrush and being gentle around the gums reduces the kind of minor tissue damage that can kick off a sore. If braces or dental appliances are causing repeated irritation, orthodontic wax over the rough edges can help protect the soft tissue inside your mouth.