Most canker sores are minor, measuring less than 5 mm across, and heal 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 the sore forming.
Rinses That Reduce Pain and Irritation
A simple saltwater and baking soda rinse is one of the most effective first steps. Mix 1 teaspoon of table salt and 1 teaspoon of baking soda into 4 cups of warm water. Swish gently for 30 seconds and spit. The alkaline solution lowers the acidity in your mouth, which reduces irritation around the sore and creates a less hostile environment for healing. You can repeat this several times a day.
Hydrogen peroxide is another option. Start with the standard 3% concentration sold at drugstores and dilute it with an equal part water, bringing it down to 1.5%. You can swish this briefly or dab it directly onto the sore with a cotton swab. Don’t swallow it. Some mild redness or irritation around the gums is normal and should fade within a few hours. After dabbing peroxide, you can follow up with a small amount of milk of magnesia applied directly to the sore, up to four times a day.
Over-the-Counter Products That Help
Topical numbing products containing benzocaine (sold as Anbesol, Orajel, Zilactin-B, and others) can take the edge off pain quickly. These come as gels, pastes, or liquids that you apply directly to the sore. They won’t dramatically shorten healing time, but they make eating and talking far more tolerable while your body does the repair work.
For better results, look for products that combine pain relief with a protective barrier. Pastes and gels tend to stick to the sore longer than liquids, shielding it from food and saliva. The earlier you start using these products after a sore appears, the more effective they are. Alcohol-free mouth rinses designed for sore mouths can also help by keeping the area clean without the burning sting of standard mouthwash.
Prescription and In-Office Options
If over-the-counter products aren’t cutting it, a dentist or doctor can prescribe stronger topical treatments containing fluocinonide, a steroid that reduces inflammation more aggressively than anything available on the shelf. These are applied directly to the sore.
For stubborn or especially painful sores, a professional treatment called chemical cauterization uses a medicated swab applied to the dried ulcer for 5 to 10 seconds. The application stings immediately, but once you rinse your mouth with water, both the stinging and the ulcer pain drop off almost right away. One application is usually enough. This approach essentially seals the sore’s surface, giving it a head start on healing. Some dental offices also offer laser treatment, though the evidence on whether it meaningfully shortens healing time compared to other methods is mixed.
Why You Keep Getting Them
If canker sores are a recurring problem, the cause often traces back to one of a few common triggers. Nutritional deficiencies are a well-documented one. Low levels of vitamin B12, folate, iron, or vitamin C are all linked to repeated outbreaks. A blood test can check for these. B12 deficiency, for example, is diagnosed when serum levels fall below 200 pg/mL, and folate deficiency at serum levels below 3 ng/mL. Correcting these deficiencies with supplements often reduces how frequently sores return.
Your toothpaste may also be a factor. Sodium lauryl sulfate (SLS), a foaming agent in most major toothpaste brands, is a known trigger for canker sores in sensitive individuals. Switching to an SLS-free toothpaste is one of the simplest changes you can make, and for some people it dramatically reduces outbreaks. Sensodyne ProNamel and several Tom’s of Maine varieties are common SLS-free options.
Other triggers include stress, hormonal shifts, mouth injuries from braces or biting your cheek, and acidic or spicy foods. Keeping a rough mental log of what preceded each outbreak can help you identify your personal pattern.
When a Canker Sore Needs Attention
A typical minor canker sore, the kind 80% of people get, clears up within one to two weeks without scarring. Major canker sores are a different story. These are larger than 10 mm (roughly the width of your pinky fingernail), can take weeks or even months to heal, and often leave scars. If your sore hasn’t started improving after two weeks, is unusually large, keeps coming back in clusters, or is accompanied by fever or difficulty swallowing, that’s worth a professional evaluation. Persistent or severe sores can sometimes signal an underlying condition like celiac disease, an immune disorder, or a more significant nutritional deficiency that needs targeted treatment.