Most canker sores heal on their own within 10 to 14 days, but you can speed up the process and reduce pain significantly with the right approach. The key is keeping the sore clean, reducing irritation, and using targeted treatments that either numb the area or promote faster tissue repair.
What’s Happening Inside the Sore
A canker sore is a shallow ulcer on the soft tissue inside your mouth, usually on the inner cheeks, lips, tongue, or the floor of your mouth. Unlike cold sores, they’re not caused by a virus and aren’t contagious. The open wound exposes nerve endings, which is why eating, drinking, and even talking can sting.
Minor canker sores, the most common type, are small (under a centimeter) and heal within 10 to 14 days without scarring. Major canker sores are larger than a centimeter, deeper, and can take up to six weeks to heal. These often leave scars. The size of your sore determines how aggressive your treatment approach should be.
Salt Water and Baking Soda Rinses
The simplest and most effective home treatment is a rinse you can make in under a minute. Mix 1 teaspoon of table salt and 1 teaspoon of baking soda into 4 cups of warm water. Swish a mouthful gently over the sore for 30 seconds, then spit. You can do this several times a day, especially after meals. The salt draws out fluid from the inflamed tissue, which reduces swelling. The baking soda creates a mildly alkaline environment that helps keep the area clean and less hospitable to bacteria that could slow healing.
Store the leftover solution in a lidded container at room temperature. It stays good for about 24 hours before you should make a fresh batch.
Over-the-Counter Pain Relief
Benzocaine gels and ointments are the most widely available numbing agents for canker sores. Apply a small amount directly to the sore up to four times a day. The numbness kicks in within a minute or two and typically lasts long enough to eat a meal without wincing. For lozenges containing benzocaine, dissolve one slowly in your mouth every two hours as needed.
Protective pastes that contain ingredients like carboxymethylcellulose form a temporary barrier over the sore, shielding it from food and saliva. These work best when applied after rinsing and drying the area as much as possible with a clean tissue. The coating helps the sore heal undisturbed and makes eating less painful.
What to Avoid While Healing
Certain foods and habits will irritate the sore and slow recovery. Acidic foods like citrus, tomatoes, and vinegar-based dressings are the biggest offenders. Spicy foods, crunchy chips, and very hot beverages also aggravate the wound. Stick to softer, bland, lukewarm foods until the sore closes up.
Your toothpaste may also be part of the problem. Sodium lauryl sulfate (SLS), a foaming agent in most toothpastes, is strongly linked to canker sore flare-ups. A systematic review found that people who switched to SLS-free toothpaste had significantly fewer ulcers, shorter healing times (about two fewer days per sore), fewer episodes overall, and less pain. If you get canker sores regularly, switching toothpaste is one of the highest-impact changes you can make. Several major brands sell SLS-free versions, often marketed for sensitive mouths.
Nutritional Gaps That Fuel Recurrence
If canker sores keep coming back, a nutritional deficiency could be driving the cycle. Vitamin B12 is the strongest link. In one study comparing people with recurrent canker sores to healthy controls, over 50% of those with recurring sores were deficient in B12, while none of the controls were. That’s a striking gap.
Iron and folate deficiencies are also associated with recurrent sores, though the connection isn’t as dramatic as with B12. If you get canker sores more than a few times a year, it’s worth asking for a blood panel that includes B12, ferritin (iron stores), and folate levels. Correcting a deficiency through diet or supplements can sometimes eliminate recurrences entirely. Good dietary sources of B12 include meat, fish, eggs, and fortified cereals. Leafy greens and legumes cover folate, while red meat and beans are solid iron sources.
Professional Treatments for Stubborn Sores
For sores that won’t quit or that cause severe pain, a dentist or doctor can use chemical cauterization. One option is a topical solution called debacterol, which chemically cauterizes the sore and can cut healing time down to about a week for serious sores. Silver nitrate is another cauterizing agent. It doesn’t necessarily speed healing, but it usually provides immediate pain relief by sealing off the exposed nerve endings.
For major canker sores or frequent severe outbreaks, prescription-strength steroid gels or mouth rinses can reduce inflammation and promote faster healing. These are typically used for a limited course and applied directly to the sore.
When a Canker Sore Needs Medical Attention
Most canker sores are a nuisance, not a danger. But certain signs suggest something more is going on. Contact a doctor or dentist if your sore lasts longer than two weeks, is larger than a centimeter (roughly the size of a pea), comes with a high fever, or if you’re getting frequent clusters of new sores before old ones have healed. Sores that are unusually large or persistent can sometimes signal an underlying condition like celiac disease, inflammatory bowel disease, or an immune system issue that warrants investigation.