Most canker sores on the tongue heal on their own within 7 to 14 days, but the right care can reduce pain and speed that timeline. These small, shallow ulcers aren’t contagious (they’re not cold sores), and they don’t require medical treatment in most cases. What they do require is keeping irritation low and giving the tissue what it needs to repair itself.
What’s Happening as It Heals
A canker sore goes through three distinct phases. First comes the prodromal stage, lasting 1 to 3 days, where you feel a tingling or burning spot on your tongue before anything is visible. By about day three, the ulcer has fully formed: a round or oval sore, usually white or yellowish with a red border, that hurts when anything touches it. This ulcerative stage lasts another 3 to 6 days. After that, the sore gradually shrinks and the pain fades as new tissue covers the wound.
Minor canker sores, the most common type, measure less than 5 millimeters across and resolve within two weeks without scarring. Major canker sores are larger than 10 millimeters (bigger than a pea) and can take several weeks to heal, sometimes leaving a scar. The tongue is one of the more painful locations because it moves constantly against your teeth and food.
Salt Water and Baking Soda Rinses
A simple rinse is the most accessible way to keep the sore clean and reduce bacteria that can slow healing. Dissolve 1 teaspoon of baking soda in half a cup of warm water and swish gently for 30 seconds, then spit. You can also use a basic salt water rinse at a similar ratio. Repeat several times a day, especially after meals. The rinse won’t sting as badly as you might expect, and it creates a less acidic environment in your mouth, which helps the tissue recover.
Over-the-Counter Pain Relief
Topical numbing gels containing benzocaine can take the edge off, particularly before eating. Apply a small amount directly to the sore up to four times a day. These products work within minutes by temporarily blocking nerve signals at the surface. Look for gels specifically labeled for oral use, since the tongue’s constant moisture makes liquids and sprays less practical.
Some people find that coating the sore with a protective paste (products labeled as “oral wound care” or canker sore patches) helps more than numbing alone. These form a barrier over the ulcer so food and your teeth don’t make direct contact, which both reduces pain and lets the tissue heal with less disruption.
What to Eat and What to Avoid
Spicy, salty, and acidic foods actively irritate an open canker sore and can delay healing. Citrus fruits, tomatoes, vinegar-based dressings, hot sauce, and chips are the most common culprits. Coffee and carbonated drinks can also sting. While you’re healing, lean toward soft, bland foods: yogurt, scrambled eggs, oatmeal, mashed potatoes, smoothies. Lukewarm or cool temperatures are easier on the sore than hot food.
If you notice that certain foods consistently trigger new canker sores, that’s worth paying attention to. Some people find that chocolate, strawberries, nuts, or cheese seem to set them off, though triggers vary widely from person to person.
When a Prescription Helps
For canker sores that are especially large or painful, a prescription steroid paste can reduce inflammation and shorten healing time. These pastes are applied directly to the sore at bedtime so the medication stays in contact with the tissue overnight. Depending on severity, you may need to apply it two or three times a day, ideally after meals. This type of treatment works best when started early, during the first day or two of the ulcer stage.
Chemical cautery is another option your dentist or doctor can perform in-office. Agents like silver nitrate or specialized solutions are applied directly to the sore to destroy the damaged tissue and seal the nerve endings, which provides almost immediate pain relief. The sore still takes the same amount of time to fully close, but the pain drops significantly right away.
Nutritional Gaps That Fuel Recurrence
If you get canker sores repeatedly, a nutritional deficiency may be playing a role. In one study of people with recurrent canker sores, about half were deficient in vitamin B12, and nearly 46% had low folate levels. Iron deficiency was less common but still present in roughly 1 in 10 patients. None of the healthy controls in the study had low B12 levels, making the contrast striking.
B12 is found in meat, fish, eggs, and dairy. Folate comes from leafy greens, legumes, and fortified grains. If you eat a limited diet, are vegetarian or vegan, or suspect a deficiency, a blood test can confirm it. Correcting these gaps often reduces how frequently canker sores return.
Habits That Help Prevent New Sores
Mechanical trauma is one of the most common triggers for tongue canker sores. Biting your tongue, brushing too aggressively, or having a sharp edge on a tooth or dental appliance can all start one. Using a soft-bristled toothbrush and being deliberate about not scrubbing the sides of your tongue helps. If a specific tooth edge or orthodontic bracket keeps catching the same spot, your dentist can smooth or adjust it.
You may have heard that switching to a toothpaste free of sodium lauryl sulfate (SLS, the ingredient that makes toothpaste foam) can reduce canker sore frequency. The evidence on this is mixed. A 2019 review found there wasn’t enough data to confirm that SLS-free toothpastes reduce how often sores occur, how long they last, or how much they hurt. That said, some individuals do report improvement after switching, and SLS-free options are inexpensive enough that it’s a low-risk experiment.
Stress and poor sleep are also well-recognized triggers. Many people notice canker sores appearing during exams, work deadlines, or periods of illness, when the immune system is under more strain.
Signs a Canker Sore Needs Medical Attention
Most canker sores are a nuisance, not a danger. But contact your doctor or dentist if a sore lasts longer than two weeks, is larger than a centimeter (about the size of a pea), or is accompanied by a high fever. Multiple sores appearing at once, sores that spread rapidly, or pain so severe that you can’t drink enough fluids also warrant a call. Persistent or unusually large ulcers occasionally need a biopsy to rule out other conditions.