Most canker sores clear up on their own within one to two weeks, but you can speed that timeline and cut the pain significantly with the right approach. The key is acting early: treatments work best when applied as soon as you notice that familiar tingling or spot forming inside your mouth.
Home Rinses That Actually Help
A simple salt water rinse is the fastest thing you can do right now. Mix about half a teaspoon of salt into a cup of warm water, swish it around the sore for 30 seconds, and spit. This draws fluid out of the swollen tissue, which temporarily reduces inflammation and creates a less hospitable environment for bacteria. You can repeat this several times a day.
Baking soda works similarly. Dissolve about a teaspoon in half a cup of warm water and use it as a rinse, or mix a small amount with water to form a paste and apply it directly to the sore. Baking soda neutralizes acids in your mouth that irritate the open ulcer, which is why it often brings noticeable relief within minutes. Some people alternate between salt water and baking soda rinses throughout the day.
A diluted hydrogen peroxide rinse (equal parts 3% hydrogen peroxide and water) can also help keep the area clean. Dab it on with a cotton swab or swish gently. Avoid swallowing any of it.
Over-the-Counter Pain Relief
Topical numbing products containing benzocaine (sold under names like Anbesol, Orabase, and Zilactin-B) are the most widely available option at pharmacies. These create a temporary numbing film over the sore, blocking pain signals for anywhere from 30 minutes to a few hours depending on the product. Pastes and gels tend to stick better than liquids, especially on sores along the gumline or inner cheek.
The important thing is timing. These products work best when applied to individual sores as soon as they appear. Waiting until a canker sore is fully developed and deeply painful means you’ve missed the window where topical treatment can meaningfully shorten healing time. Apply with a clean finger or cotton swab, and try not to eat or drink for at least 15 minutes afterward so the product stays in place.
Prescription Options for Stubborn Sores
If over-the-counter products aren’t cutting it, a doctor or dentist can prescribe stronger treatments. A topical steroid paste containing fluocinonide reduces inflammation directly at the ulcer site, helping both pain and healing speed. For people dealing with multiple sores at once, a prescription mouth rinse containing a steroid or a numbing agent like lidocaine can cover more territory than a spot treatment.
Chemical cautery is another option your dentist may offer. A topical solution called Debacterol chemically seals the sore, reducing healing time to about a week even for more serious ulcers. Silver nitrate is a similar cauterizing agent that reliably reduces pain, though it hasn’t been shown to speed up healing the way Debacterol does. Both are applied in a single office visit.
Laser treatment is a newer approach some dental offices now provide. A low-level laser is directed at the sore for a short session, and in many cases a single treatment is enough to promote healing. It’s typically reserved for patients with frequent or severe outbreaks.
Why You Keep Getting Them
If canker sores are a recurring problem, the cause is often something you can identify and change. The most common triggers include acidic or spicy foods (citrus, tomatoes, chips with sharp edges), stress, hormonal shifts, and minor injuries to the mouth lining from braces, aggressive brushing, or accidentally biting your cheek.
Nutrient deficiencies play a larger role than most people realize. Low levels of vitamin B12, iron, and folic acid are all linked to recurrent canker sores. In documented cases, patients with B12 levels well below the normal range experienced repeated outbreaks that resolved after supplementation. If you’re getting canker sores more than two or three times a year, it’s worth having your levels checked with a simple blood test.
Your toothpaste may also be a factor. Many conventional toothpastes contain sodium lauryl sulfate (SLS), a foaming agent that can irritate the delicate tissue inside your mouth. In a study of patients with recurrent oral ulcers, more than half reported fewer outbreaks after switching to an SLS-free toothpaste for three months. Brands like Sensodyne, Biotene, and Verve are widely available SLS-free options.
How to Prevent New Sores
Once you’ve identified your personal triggers, prevention becomes straightforward:
- Switch to an SLS-free toothpaste and use a soft-bristled brush to minimize irritation to your mouth lining.
- Avoid your trigger foods during high-stress periods when you’re most vulnerable. For many people, this means cutting back on citrus, vinegar-based dressings, and crunchy snacks with sharp edges.
- Cover sharp dental work. If braces or a rough tooth edge keep cutting the same spot, dental wax provides a barrier while you arrange a fix.
- Address nutritional gaps. A daily multivitamin covering B12, folate, and iron can help if your diet is limited or your blood work shows borderline levels.
When a Canker Sore Needs Attention
Most canker sores are minor, mildly painful, and gone within a few days to two weeks. But about 10% of people who get recurrent canker sores develop what’s classified as major aphthous ulcers. These exceed 1 centimeter in diameter (roughly the width of your pinky fingernail), can appear on tougher tissue like the roof of your mouth, take up to six weeks to heal, and sometimes leave scars.
A sore that lasts longer than two weeks without improvement, grows unusually large, comes with fever, or makes it difficult to eat or drink enough fluids is worth having evaluated. The same goes for outbreaks that happen frequently and don’t respond to trigger avoidance. A dentist or oral medicine specialist can rule out underlying conditions and set up a treatment plan that goes beyond managing individual sores one at a time.