Most mouth ulcers (canker sores) heal on their own within 10 to 14 days, but the right treatments can cut pain significantly and speed up recovery. These small, round sores with a white or yellow center and red border appear inside the mouth, on the tongue, inner cheeks, or gums. While you wait for healing, several home remedies, over-the-counter products, and lifestyle changes can make a real difference.
Canker Sores vs. Cold Sores
Before treating a mouth ulcer, make sure you’re dealing with the right thing. The easiest way to tell the difference is location. Canker sores appear inside the mouth. Cold sores (fever blisters) appear outside the mouth, typically around the border of the lips. They also look different: canker sores are usually a single round white or yellow sore with a red border, while cold sores are clusters of small, fluid-filled blisters. Cold sores are caused by the herpes simplex virus and require antiviral treatment, so the remedies below won’t help with those.
Salt Water and Other Home Remedies
A warm salt water rinse is the simplest and most accessible treatment. Mix one teaspoon of salt into one cup of warm (not hot) water. Swish it around your mouth for five to ten seconds, then spit it out. You can repeat this several times a day. Salt water helps reduce bacteria around the ulcer and draws fluid out of the swollen tissue, which eases discomfort.
Another option you can make at home: mix equal parts liquid antacid (the kind containing magnesium hydroxide) with liquid antihistamine containing diphenhydramine. Swish a small amount around the ulcer and spit it out. This combination coats the sore and provides temporary numbing relief. You can also dab a small amount of honey directly on the ulcer, which some people find soothing due to its natural antibacterial properties.
Avoid acidic or spicy foods while the ulcer is healing. Citrus fruits, tomatoes, hot peppers, and vinegar-based dressings can all irritate the sore and make pain worse. Eating softer foods and drinking through a straw can help you avoid bumping the ulcer.
Over-the-Counter Gels and Pastes
Numbing gels containing benzocaine (sold as Orajel and Anbesol) are widely available and provide fast, temporary pain relief when dabbed directly on the sore. Viscous lidocaine, applied with a cotton swab several times daily, works similarly by blocking pain signals at the surface.
Protective pastes like Orabase or Zilactin-B take a different approach. Instead of numbing the ulcer, they coat it with a barrier layer that shields it from food, drinks, and your teeth. This can make eating and talking much more comfortable. For best results, dry the area gently with a tissue before applying the paste so it sticks properly.
When Ulcers Need Prescription Treatment
If you get frequent or unusually painful ulcers, a dentist or doctor may prescribe a topical steroid paste or rinse. These work by reducing the inflammation driving the pain and swelling. Steroid pastes are applied directly to the sore, and research confirms they reduce symptoms without affecting your body’s hormone balance, since the medication stays local to the mouth. That said, steroid treatments don’t prevent future outbreaks. They manage the current one.
For stubborn, large ulcers, some clinicians offer chemical cauterization using silver nitrate. In one clinical trial, 60% of patients treated with silver nitrate had fully healed ulcers by day seven, compared to 32% in the placebo group. The treated group reported an average healing time of just 2.7 days after the procedure, versus 5.5 days without it. This is a quick in-office procedure, not something you’d do at home.
A protective oral rinse called Gelclair is another prescription option. It forms a film over the ulcer that shields exposed nerve endings, reducing pain during eating and drinking.
Switch to SLS-Free Toothpaste
One of the most effective preventive steps is also one of the simplest: switch your toothpaste. Sodium lauryl sulfate (SLS) is a foaming agent found in most toothpastes, and it’s a well-documented trigger for recurrent canker sores. A systematic review highlighted by the American Dental Association found that people using SLS-free toothpaste developed significantly fewer ulcers, experienced shorter ulcer duration, had fewer recurrent episodes, and reported less pain compared to those using standard toothpaste.
Brands like Sensodyne, Biotene, and several others make SLS-free formulas. Check the ingredients list for “sodium lauryl sulfate.” If you get canker sores more than a few times a year, this single change is worth trying before anything else.
Nutritional Deficiencies and Recurring Ulcers
Chronic mouth ulcers can signal that your body is low on certain nutrients. Iron, folate, and vitamin B12 deficiencies have all been linked to recurrent outbreaks. If you’re getting canker sores frequently and can’t identify an obvious trigger like stress or a sharp tooth, ask your doctor to check your blood levels for these nutrients. Correcting a deficiency through diet or supplements can reduce how often ulcers come back.
In rarer cases, recurring mouth ulcers are associated with celiac disease or other immune-related conditions. Most people with occasional canker sores are otherwise healthy, but frequent, severe, or unusually large ulcers warrant a closer look.
How Long Healing Takes
Minor canker sores, the kind most people get, typically resolve in one to two weeks without treatment. The first three to four days tend to be the most painful, after which the ulcer gradually shrinks and the pain fades. Using the treatments above can shorten that painful window considerably.
Major aphthous ulcers, which are larger and deeper, can take several weeks or even months to heal and may leave a scar. These are less common but significantly more disruptive.
Any mouth sore that lasts longer than three weeks should be evaluated by a healthcare provider. Persistent sores that don’t heal are one of the early warning signs of oral cancer, and a biopsy is strongly recommended for lesions that remain after two weeks once obvious irritants (like a rough tooth edge) have been addressed. This doesn’t mean every slow-healing canker sore is dangerous, but it’s the kind of thing worth getting checked.