Most canker sores heal on their own within 10 to 14 days, but the right combination of pain relief and protective treatments can shorten that timeline and make the wait far more bearable. These small, round ulcers with a white or yellow center and red border form inside the mouth, on the inner cheeks, lips, or tongue. Unlike cold sores, they aren’t caused by a virus and aren’t contagious.
Why Canker Sores Form
Canker sores are driven by your immune system, not by an infection you can “catch.” Immune cells attack the lining of your mouth, destroying small patches of tissue and creating the painful crater you see. This process is fueled by local inflammation, with elevated levels of signaling molecules that recruit more immune cells to the area and keep the damage going.
The triggers that set off this response vary from person to person, but the most common ones are physical trauma (biting your cheek, a sharp edge on braces), psychological stress, hormonal shifts during the menstrual cycle, and nutritional deficiencies. About a third of people with recurring canker sores have a family history of them, pointing to a genetic component in how the immune system reacts to everyday mouth bacteria.
Treatments That Speed Healing
No single product eliminates a canker sore overnight, but several over-the-counter options are backed by clinical evidence. Your best strategy is layering a protective or anti-inflammatory paste with a rinse.
Anti-inflammatory pastes: Amlexanox 5% paste significantly reduces ulcer size and shortens both healing time and pain duration, with measurable improvement by day three. Prescription steroid pastes containing triamcinolone work similarly, reducing inflammation directly at the sore. You apply a small amount with a cotton swab after meals and at bedtime, pressing gently to form a thin film rather than rubbing it in.
Debacterol: This topical treatment, available by prescription, reduced pain scores dramatically compared to placebo by day three (a 45-point drop on a 100-point scale versus 15 points for placebo) and resolved symptoms more effectively by day six. It works by chemically sealing the ulcer surface.
Silver nitrate: A dentist can apply silver nitrate directly to the sore. It doesn’t speed overall healing, but it’s effective at eliminating pain quickly, with more patients reporting zero pain on day one compared to other options.
OTC numbing gels: Products containing benzocaine provide temporary pain relief on contact. They won’t shorten healing, but they make eating and talking significantly less painful for 15 to 30 minutes at a time.
Rinses That Help
A simple saltwater rinse is one of the most accessible remedies. Dissolve about half a teaspoon of salt in a cup of warm water, swish for 30 seconds, and spit. A baking soda rinse works similarly: one teaspoon of baking soda in half a cup of warm water. Both help keep the area clean and reduce irritation. You can repeat either rinse several times a day.
Antiseptic mouthwashes offer a modest but measurable benefit. In clinical trials, Listerine (containing menthol, thymol, and eucalyptol) shortened canker sore outbreaks by nearly a full day compared to placebo and reduced pain severity on a 10-point scale. Chlorhexidine mouthwash, available over the counter in some formulations, cut overall ulcer burden roughly in half compared to placebo in studies tracking sore frequency and severity over time.
What to Avoid While You Heal
Acidic foods like tomatoes, citrus fruits, and vinegar-based dressings will sting on contact and can slow healing. Spicy foods and anything with rough or sharp edges (chips, crusty bread, hard pretzels) physically irritate the open sore. Stick to softer, blander foods until the ulcer closes. Drinking through a straw can help liquids bypass the sore if it’s on your inner lip or cheek.
Preventing Future Canker Sores
Switch Your Toothpaste
Sodium lauryl sulfate (SLS), the foaming agent in most toothpastes, is a well-documented contributor to canker sore formation. Dental researchers in both the U.S. and Norway have confirmed this link. Switching to an SLS-free toothpaste is one of the simplest changes you can make, and for many people it significantly reduces how often sores come back. Brands like Sensodyne, Biotene, and some versions of Tom’s of Maine are SLS-free.
Check for Nutritional Gaps
Vitamin B12 deficiency has a striking connection to recurring canker sores. In one study, over half of patients with recurrent ulcers had B12 levels below normal, compared to zero in the control group. Folate deficiency showed up in nearly 46% of patients as well. Iron deficiency played a smaller role. If you get canker sores frequently, it’s worth asking about a blood test for these levels, especially if you follow a vegetarian or vegan diet, which carries a higher risk of B12 deficiency.
Manage Stress and Track Triggers
Stress is one of the most consistent triggers. Outbreaks tend to cluster around high-pressure periods like exams, deadlines, or major life changes. Keeping a simple log of when sores appear alongside what you’ve eaten, your stress level, and your menstrual cycle (if applicable) can help you identify your personal pattern. Some people find that specific foods, particularly chocolate, coffee, nuts, or strawberries, reliably trigger outbreaks. Quitting smoking, surprisingly, can also trigger canker sores in some people.
Minor Sores vs. Major Sores
Most canker sores are the minor type: small, round, and gone within two weeks without scarring. Major aphthous ulcers are larger, deeper, and can take up to six weeks to heal, sometimes leaving a scar. If your sore is unusually large, hasn’t started improving after two weeks, comes with a fever, or you’re getting multiple sores at once on a regular basis, that pattern warrants a professional evaluation. Persistent or unusually large mouth sores can occasionally signal an underlying condition like celiac disease, an immune disorder, or a nutritional deficiency that needs targeted treatment.
Canker Sores vs. Cold Sores
These two get confused constantly, but they’re completely different. Canker sores form only inside the mouth, on soft tissue like the inner cheeks, lips, or tongue. They appear as a single round white or yellow sore with a red border. They are not caused by a virus and cannot spread to another person. Cold sores (fever blisters) are caused by herpes simplex virus, form on or around the outer lips, start as fluid-filled blisters, and are contagious. If your sore is on the outside of your lip or started as a blister, it’s a cold sore and needs antiviral treatment instead.