Most canker sores heal on their own within 10 to 14 days without leaving a scar. But several treatments can speed that timeline, cut the pain, and reduce how often sores come back. What works best depends on the size of your sore and how frequently you get them.
How Canker Sores Heal Naturally
Before a canker sore is visible, you may notice an itchy or burning sensation in one spot inside your mouth. Within hours, the area turns red and small white papules form, which break open into an ulcer that expands over the next 48 to 72 hours. After that peak, the body begins regenerating the surface tissue, and a typical minor sore (just a few millimeters wide) closes up in 10 to 14 days.
Larger sores, classified as major canker sores at one to three centimeters, can persist for up to six weeks. These rarely leave scars but are significantly more painful and disruptive. A third type, herpetiform canker sores, appear as clusters of pinhead-sized ulcers that can merge together. Because of that merging, they’re the most likely type to scar.
Saltwater and Baking Soda Rinses
A simple rinse is the most accessible home treatment and genuinely helps. An alkaline saline solution reduces acidity in the mouth, which eases irritation and creates a friendlier environment for tissue repair. St. Jude Children’s Research Hospital recommends mixing one teaspoon of table salt and one teaspoon of baking soda into four cups of warm water. Swish for 30 to 60 seconds a few times a day, especially after meals. It won’t numb the pain instantly, but consistent rinsing can shorten healing time for mild sores.
Over-the-Counter Gels and Pastes
Pharmacy shelves carry two main categories of canker sore products: numbing agents and anti-inflammatory pastes. Numbing gels containing lidocaine or benzocaine provide satisfactory short-term pain relief by blocking nerve signals at the sore’s surface. You apply them directly and get temporary numbness, which is most useful before eating.
The more effective OTC option for actual healing is amlexanox 5% paste. When applied during the early tingling stage, it reduces both the size of the ulcer and how long it lasts. A cream containing 5-aminosalicylic acid has also shown faster healing and meaningful pain reduction compared to doing nothing. Both work best when you catch the sore early, ideally during that initial burning or tingling phase before the ulcer fully forms.
Prescription Treatments for Severe Sores
If you get large or frequent canker sores, a dentist or doctor can prescribe a steroid-based mouth rinse. These typically contain triamcinolone or dexamethasone in low concentrations. You swish a small amount (about a teaspoon) for one minute after meals and before bed, then spit it out and avoid eating or drinking for 30 minutes. The steroid calms the immune response driving the ulcer, which shrinks it faster and dulls the pain. More severe cases may call for a higher-concentration rinse.
Chemical Cauterization
For a sore that’s already formed and intensely painful, chemical cauterization offers the fastest pain relief available. A dentist applies silver nitrate or a product called Debacterol directly to the ulcer, essentially burning the nerve endings on its surface. In a randomized controlled trial, 70% of patients treated with silver nitrate had significant pain reduction within one day, compared to just 11% of those given a placebo. The catch: cauterization doesn’t make the sore heal faster. By day seven, healing rates were virtually identical between both groups (83% versus 89%). So it’s a pain management tool, not a cure.
Laser Treatment
Low-level laser therapy is a newer option some dental offices provide. A cold laser is applied to the sore for a few seconds, and clinical trials have shown it can produce immediate pain relief in a single session. After treatment, patients typically report the ulcer is pain-free, with only mild sensitivity to touch remaining. It’s not widely available and usually costs out of pocket, but for people with frequent, debilitating sores, it can be worth asking about.
Nutritional Gaps That Cause Recurring Sores
If you get canker sores repeatedly, the cause may be nutritional rather than something you can fix with topical treatment. Three deficiencies are closely linked to recurrent outbreaks: vitamin B12, iron, and folate. Your doctor can check all three with a simple blood draw. Low B12 (below 180 ng/L), low ferritin (below 11 ng/mL for women, 15 ng/mL for men), or low folate (below 4.0 ng/mL) each independently raise your risk. Correcting the deficiency through diet or supplements often reduces how frequently sores appear.
Common dietary sources of these nutrients include red meat, eggs, and dairy for B12; leafy greens and legumes for folate; and red meat, shellfish, and fortified cereals for iron. If you follow a vegetarian or vegan diet, B12 supplementation is especially worth considering.
What Triggers Canker Sores
Beyond nutritional deficiencies, several everyday factors can set off an outbreak. Mechanical trauma is one of the most common: biting your cheek, a sharp edge on a tooth, or aggressive brushing can all damage the lining of your mouth enough to trigger a sore. Stress and hormonal shifts are well-documented triggers too, which is why many people notice outbreaks during exams, travel, or around menstruation.
Acidic and spicy foods don’t cause canker sores directly, but they irritate existing tissue damage and can tip a vulnerable spot into a full ulcer. Some people find that switching toothpaste helps, though a controlled study found that removing sodium lauryl sulfate (a common foaming agent) from toothpaste did not significantly change ulcer frequency or severity. Individual triggers vary, so tracking your outbreaks alongside diet, stress, and habits is the most reliable way to identify yours.
When a Sore Needs Professional Attention
A canker sore that hasn’t healed after two weeks deserves a closer look from a dentist or doctor. Persistent oral ulcers that last beyond that window, interfere with eating or speaking, or don’t respond to removing obvious irritants are generally recommended for biopsy to rule out other conditions, including oral cancer. Sores accompanied by high fever, difficulty swallowing, or sores that keep returning in clusters also warrant evaluation, as recurrent aphthous stomatitis can sometimes signal an underlying immune or gastrointestinal condition like celiac disease or Crohn’s disease.