Most canker sores on the gums heal on their own within one to three weeks, but you can speed that process and cut the pain significantly with the right combination of rinses, topical treatments, and trigger avoidance. Minor canker sores, the most common type, are smaller than a centimeter across and resolve without scarring. Major canker sores are larger, extremely painful, and can take months to heal, sometimes leaving scars behind.
Salt Water and Baking Soda Rinses
The simplest thing you can do right now is rinse your mouth with a solution of 1 teaspoon of baking soda dissolved in half a cup of warm water. This shifts the pH inside your mouth toward alkaline, creating an environment that’s less irritating to the open sore. A plain salt water rinse works similarly: dissolve half a teaspoon of table salt in the same amount of warm water. Swish gently for 30 to 60 seconds, then spit. Repeat three to four times a day, especially after meals, when food particles are most likely to irritate the sore.
Over-the-Counter Numbing Gels
Benzocaine gels designed for mouth sores contain 20% benzocaine, which numbs the tissue on contact. Dry the area around the sore with a clean tissue first, then apply a small amount directly to the ulcer. The numbing effect lasts about 15 to 30 minutes, enough to eat or drink without wincing. Reapply up to four times a day.
Milk of magnesia is another option you may already have at home. It contains magnesium hydroxide, which neutralizes acids in the mouth and coats the sore with a thin protective layer. Dab a small amount onto the ulcer with a cotton swab a few times daily.
Adhesive Patches for Gum Sores
Canker sore patches are small tablets you press directly onto the ulcer. Within about 30 minutes, the tablet dissolves into a clear gel-like bandage that seals and protects the sore for several hours. This barrier keeps food, drinks, and your tongue from rubbing against the raw tissue, which is especially useful on the gums where chewing creates constant friction. Most patches contain a mild dose of menthol for light pain relief. They work best on sores you can reach easily and press firmly against for a few seconds.
Switch to an SLS-Free Toothpaste
Sodium lauryl sulfate, listed as SLS on ingredient labels, is a foaming agent in most mainstream toothpastes. It’s also a significant canker sore trigger. In one study, people with recurrent canker sores averaged 14.3 ulcers over three months while using an SLS toothpaste, then just 5.1 ulcers after switching to an SLS-free version. That’s a 64% reduction from changing toothpaste alone. A 2019 review of four clinical trials involving 124 participants confirmed the pattern: SLS-free toothpaste reduced the number of ulcers, how long each one lasted, and the pain they caused.
If you get canker sores more than a couple of times a year, switching toothpaste is one of the highest-impact changes you can make. Brands marketed as “sensitive” or “natural” are more likely to be SLS-free, but check the ingredients to be sure.
Nutritional Deficiencies That Fuel Recurrence
Recurring canker sores are strongly linked to low vitamin B12. In one study comparing people with recurrent oral ulcers to a control group, half of the canker sore patients were deficient in B12 (levels below 220 pg/mL), while none of the controls were deficient. The average B12 level among deficient patients was just 124 pg/mL, well below normal range.
Iron deficiency also plays a role for some people, though the connection is less dramatic than B12. If you’re getting canker sores frequently, especially clusters of them, it’s worth asking your doctor to check your B12 and iron levels with a simple blood test. Supplementing a genuine deficiency can reduce how often sores come back.
When a Canker Sore Needs Prescription Treatment
If over-the-counter options aren’t enough, prescription-strength treatments exist. The most common are steroid-based rinses or ointments that reduce inflammation directly at the sore. Your dentist or doctor may prescribe a steroid rinse you swish and spit four times a day (after meals and before bed), or a steroid ointment applied as a thin film to the dried tissue. These work by calming the immune response that’s driving the ulcer, which shortens healing time and reduces pain substantially. For severe or widespread outbreaks, oral steroids are sometimes used short-term.
Everyday Habits That Help Sores Heal Faster
While a canker sore is active on your gums, what you avoid matters as much as what you apply. Acidic foods like citrus, tomatoes, and vinegar-based dressings sting on contact and can slow healing. Spicy foods do the same. Crunchy or sharp-edged foods like chips and crusty bread can physically reopen the sore.
Brush gently around the area with a soft-bristled toothbrush. Aggressive brushing near the sore tears the fragile new tissue trying to form. If the sore is right at the gumline, angle your brush away from it and rely on your rinses to keep that spot clean.
Staying hydrated helps too. A dry mouth concentrates acids and bacteria around the ulcer. Sipping water throughout the day keeps the tissue moist and dilutes irritants.
How Long Healing Takes
Minor canker sores, the kind most people get, typically close up within two to three weeks without leaving any trace. Herpetiform canker sores, which look like clusters of tiny pinpoint ulcers rather than a single sore, heal in about two weeks and also don’t scar. Major canker sores, those bigger than a centimeter, are a different experience. They can persist for months and often leave scar tissue behind.
Any single ulcer that hasn’t healed after two weeks warrants a professional look. Persistent oral ulcers can sometimes indicate other conditions that need evaluation, and a dentist can determine whether a biopsy or further testing makes sense.