Most canker sores heal on their own within 10 to 14 days, but the right treatments can cut pain significantly and speed that timeline. What works best depends on how severe the sore is, whether it keeps coming back, and how much it interferes with eating and drinking.
Minor vs. Major Canker Sores
The small, round ulcers most people get are minor canker sores. They’re painful but self-limiting, typically clearing up in 10 to 14 days without treatment. Major canker sores are deeper, larger, and can last up to a month. They’re also more likely to leave a scar. If your sore is still there after two weeks or is large enough to make eating difficult, it’s worth treating more aggressively or having a doctor look at it.
Over-the-Counter Gels and Rinses
The fastest relief comes from topical products applied directly to the sore. Look for gels or pastes containing benzocaine, a numbing agent found in products like Anbesol and Orabase. These temporarily block pain signals at the surface and work best when applied as soon as you notice a sore forming. Reapply as directed on the label, usually up to four times a day.
Hydrogen peroxide rinses (like Orajel Antiseptic Mouth Sore Rinse) serve a different purpose. Rather than numbing, they help clean the ulcer and reduce bacteria around it, which can support faster healing. You can also make a simple rinse at home by mixing equal parts 3% hydrogen peroxide and water, dabbing it on the sore with a cotton swab.
Salt Water and Baking Soda Rinses
A warm salt water rinse is the simplest home treatment. Dissolve about half a teaspoon of salt in a cup of warm water, swish gently for 15 to 30 seconds, and spit it out. This draws fluid from the swollen tissue, which temporarily reduces pain and helps the sore heal. You can repeat this several times a day, especially after meals.
Baking soda works similarly. Mix about a teaspoon into a cup of warm water and rinse the same way. Baking soda creates a mildly alkaline environment that can neutralize acids in the mouth and soothe irritated tissue. Some people make a paste with a small amount of water and apply it directly to the sore for a few minutes before rinsing, which delivers a more concentrated effect.
Prescription Options for Severe Sores
If over-the-counter products aren’t enough, doctors and dentists have stronger tools. Prescription corticosteroid gels reduce inflammation and are particularly useful for large or especially painful sores. These are applied directly to the ulcer, usually a few times a day for a set period.
For sores that need faster resolution, a dentist can apply a chemical cautery agent called Debacterol. It contains sulfonated phenolics that essentially seal the ulcer surface in a single in-office application. The treatment destroys the damaged tissue on top of the sore, which can dramatically shorten healing time and relieve pain almost immediately.
Lidocaine viscous rinse is another prescription option focused purely on pain control. You swish it around the sore until the pain subsides, then spit it out. It can be used as needed but no more than every three hours, and no more than eight doses in 24 hours. Because it numbs your mouth and throat, avoid eating for at least an hour after using it to prevent accidentally biting your cheek or choking.
Reducing Pain While You Heal
Beyond medications, small changes to what you eat and how you eat it make a real difference. Acidic foods like tomatoes, citrus fruits, and vinegar-based dressings irritate open ulcers. Spicy foods and anything with sharp edges (chips, crusty bread, raw vegetables) can re-traumatize the sore and delay healing. Stick to softer, blander foods when the pain is at its worst, usually the first four or five days.
Cold foods like yogurt, smoothies, and ice chips can temporarily numb the area. Drinking through a straw helps liquids bypass a sore on the front of the mouth or lips.
Switch to SLS-Free Toothpaste
If you get canker sores regularly, your toothpaste may be part of the problem. Most commercial toothpastes contain sodium lauryl sulfate (SLS), a foaming detergent that can irritate the lining of your mouth. A meta-analysis of studies involving people with recurrent canker sores found that switching to SLS-free toothpaste reduced the number of ulcers by about one per cycle, shortened their duration by roughly two days, and significantly lowered pain levels. It also reduced the number of separate episodes.
SLS-free options are widely available. Brands like Sensodyne (some formulas), Biotene, and Verve all skip this ingredient. Check the inactive ingredients list on the back of the tube. This is one of the simplest changes you can make if canker sores are a recurring issue.
Nutritional Deficiencies and Recurrence
Recurrent canker sores are sometimes a sign that your body is low on certain nutrients, particularly vitamin B12. In one study comparing people with recurring canker sores to healthy controls, over 50% of canker sore patients were deficient in B12, while none of the controls were. Among those who received B12 supplementation, 73% recovered completely.
Iron and folate deficiencies have also been linked to recurrent oral ulcers, though the association isn’t as strong as with B12. If you’re getting canker sores frequently (several times a year or more), it’s reasonable to ask your doctor to check your B12, iron, and folate levels with a simple blood test. Correcting a deficiency can sometimes stop the cycle entirely.
Common Triggers to Avoid
Beyond nutritional gaps and toothpaste, several other factors are known to trigger canker sores. Minor mouth injuries are a big one: biting your cheek, brushing too aggressively, or irritation from braces or ill-fitting dental work can all set off an ulcer. Emotional stress is another well-documented trigger, though the mechanism isn’t fully understood.
Certain foods seem to provoke canker sores in susceptible people even beyond their acidity. Chocolate, coffee, strawberries, eggs, nuts, and cheese are commonly reported triggers, though the specific foods vary from person to person. Keeping a rough mental log of what you ate before an outbreak can help you identify your own patterns over time.
Hormonal changes during menstruation trigger canker sores in some women, as do periods of illness when the immune system is suppressed. If you notice sores appearing alongside other symptoms like fatigue, joint pain, or digestive issues, that pattern is worth mentioning to a doctor, since recurrent oral ulcers can occasionally signal an underlying condition like celiac disease or an autoimmune disorder.