Most canker sores heal on their own in 4 to 14 days, but the right combination of treatments can cut that timeline significantly. The key is reducing inflammation, keeping the sore clean, and avoiding irritants that slow the process down. Here’s what actually works.
How Long Canker Sores Normally Take to Heal
Minor canker sores, the most common type at 2 to 5 mm across, typically resolve in 4 to 14 days without any treatment. Major canker sores (over 1 cm) can last anywhere from 10 days to 6 weeks. Herpetiform canker sores, which appear as tiny clusters of 1 to 2 mm ulcers, usually clear up in 7 to 10 days. Knowing your baseline helps you gauge whether a treatment is actually making a difference or whether the sore was just running its course.
Salt Water Rinses
Rinsing with warm salt water is the most accessible first step. Lab research shows that salt solutions in the 0.9 to 1.8% range promote the migration of gum tissue cells, which is part of wound repair. That said, the scientific evidence for salt water speeding oral ulcer healing specifically is still limited. What salt water reliably does is keep the area clean and reduce bacterial buildup around the sore, which helps prevent it from getting worse. Dissolve about half a teaspoon of salt in a cup of warm water and swish gently for 30 seconds, several times a day.
Antiseptic Mouth Rinses
Chlorhexidine-based mouth rinses offer more measurable results. In clinical trials, a 1% chlorhexidine gel reduced average ulcer duration from about 7.8 days to 4.8 days. That’s roughly a 3-day improvement. Chlorhexidine rinses also reduce pain severity during the healing window. You can find chlorhexidine mouthwashes over the counter in most pharmacies, though some formulations require a prescription depending on your country. The gel form appears to work better than the liquid rinse for shortening healing time.
Over-the-Counter Pain and Healing Products
Topical gels and pastes containing numbing agents like benzocaine provide immediate pain relief and create a protective barrier over the sore. This barrier shields the ulcer from food, drinks, and friction, all of which slow healing. Products with hyaluronic acid, a compound that supports tissue repair, have also shown benefit in reducing lesion size. Look for oral wound gels or canker sore patches at your pharmacy. Apply them after eating and before bed for the most uninterrupted coverage.
Prescription Steroid Treatments
If your canker sores are large, extremely painful, or keep coming back, a prescription-strength steroid paste can make a real difference. Film-forming steroid formulations reduce lesion size by about 38% after 4 days and roughly 70% after 7 days. These work by suppressing the inflammatory response that drives the ulcer’s size and pain. Your dentist or doctor can prescribe a topical paste that you apply directly to the sore. Starting the steroid early, ideally during the tingling stage before the ulcer fully forms, gives the best results.
Laser Treatment at the Dentist
Low-level laser therapy is a newer option offered by some dental offices. In one controlled study, canker sores treated with laser healed in an average of 5 days compared to about 8 days without treatment. The procedure is painless, takes just a few minutes, and often provides immediate pain relief. It’s not widely available everywhere, and it typically isn’t covered by insurance, but it’s worth asking your dentist about if you deal with frequent or severe sores.
What to Avoid While You’re Healing
Certain everyday habits actively slow canker sore healing. Acidic foods like citrus, tomatoes, and vinegar-based dressings irritate the open tissue and can make the sore larger. Spicy foods and crunchy snacks cause direct mechanical damage. Hot beverages are another common culprit.
Your toothpaste may also be a factor. A systematic review of clinical trials found that toothpaste containing sodium lauryl sulfate (SLS), a foaming agent in most mainstream brands, significantly increases the number of ulcers, their duration, the number of outbreaks, and pain levels compared to SLS-free alternatives. Switching to an SLS-free toothpaste is one of the simplest changes you can make, both for the current sore and for preventing future ones. Brands like Sensodyne, Biotene, and several others sell SLS-free formulations.
Nutritional Gaps That Fuel Recurrence
If you get canker sores frequently, a nutritional deficiency could be driving the cycle. Research has found that roughly 15 to 18% of people with recurrent canker sores are deficient in vitamin B12, iron, or folate. People with chronic canker sores consume, on average, 7% less B12 and 20% less folate than people without them. These aren’t dramatic deficiencies, which is exactly why they go unnoticed.
Correcting the deficiency through diet or supplements leads to measurable improvement in outbreak frequency and severity. Good sources of B12 include meat, fish, eggs, and fortified cereals. Folate is abundant in leafy greens, beans, and citrus. If you suspect a deficiency, a simple blood test can confirm it and guide supplementation.
Canker Sores vs. Cold Sores
These are completely different conditions that require different treatments. Canker sores appear inside the mouth, on the inner cheeks, lips, or tongue. They look like a single round white or yellow sore with a red border. Cold sores appear on the outside of the mouth, around the lips, as a cluster of small fluid-filled blisters. Cold sores are caused by the herpes simplex virus and are contagious. Canker sores are not viral and cannot be spread to another person. If your sore is on the outer lip and looks blistered, the treatments in this article won’t apply.
Signs Your Canker Sore Needs Medical Attention
A typical minor canker sore doesn’t need professional treatment. But certain patterns suggest something more is going on. See your dentist or doctor if your sore is larger than 1 centimeter, lasts longer than two weeks, or if you experience more than three outbreaks per month. Accompanying symptoms like fever, fatigue, abdominal pain, eye discomfort, or rashes on other parts of your body can indicate that the ulcers are connected to a systemic condition rather than a simple local irritation. About 15% of canker sore patients have the major form, which often requires prescription management to heal properly.