Most canker sores heal on their own within one to two weeks, but the right treatments can cut pain significantly and speed things along. These small, round ulcers on the inside of your mouth are not dangerous, but they can make eating, drinking, and talking miserable. Here’s what actually works to treat them.
Rinses That Reduce Pain and Inflammation
A simple rinse is the fastest thing you can do at home. The Mayo Clinic recommends dissolving 1 teaspoon of baking soda in half a cup of warm water and swishing it around the sore. This neutralizes acids in your mouth and creates a less irritating environment for the ulcer to heal. You can repeat this several times a day, especially after meals.
Salt water rinses work similarly. Dissolve about half a teaspoon of table salt in a cup of warm water and swish gently for 30 seconds before spitting. Salt draws fluid out of the inflamed tissue, which can temporarily shrink swelling and numb the area. Both rinses sting briefly on contact, but the relief afterward is worth it.
Over-the-Counter Treatments
Topical gels and pastes containing benzocaine (a numbing agent) are widely available at pharmacies. You apply them directly to the dried sore, and they form a temporary protective layer that blocks food and saliva from hitting the raw tissue. Reapply as needed throughout the day, particularly before meals.
Protective pastes that stick to the sore and shield it while you eat can also help. Look for products specifically labeled for oral ulcers or canker sores. Hydrogen peroxide rinses (diluted to half strength with water) are another option for keeping the area clean, though they can be harsh if overused.
When Prescription Treatment Helps
For canker sores that are large, unusually painful, or keep coming back, a dentist or doctor can prescribe stronger options. Corticosteroid rinses, like dexamethasone elixir, reduce inflammation directly. You swish a small amount in your mouth and spit it out, typically twice a day. Steroid pastes applied to the dried ulcer two to four times daily are another common prescription approach.
For severe recurrent outbreaks, doctors sometimes prescribe antibiotic rinses or immune-modulating pastes that target the inflammatory process driving the ulcers. These are reserved for cases where simpler treatments haven’t worked.
Foods to Avoid While Healing
What you eat matters as much as what you apply. Acidic foods are the biggest aggravators: citrus fruits, tomatoes, strawberries, and fizzy drinks all irritate the open tissue and can delay healing. Alcohol has the same effect. Spicy and heavily salted foods irritate the mucous lining and intensify pain on contact.
Texture matters too. Hard, crunchy, or sharp-edged foods like crusty bread, chips, and raw vegetables can physically scrape the sore and reopen healing tissue. Stick to soft, cool, or room-temperature foods while you’re dealing with an active ulcer. Yogurt, smoothies, mashed potatoes, and scrambled eggs are all easy choices.
Nutritional Gaps That Cause Recurring Sores
If you get canker sores two or three times a year or more, the problem may not be in your mouth. Deficiencies in vitamin B12, folate, and vitamin C are closely linked to recurrent outbreaks. A review in Frontiers in Oral Health found that people with B12 levels below 200 pg/mL and folate levels below 3 ng/mL were significantly more likely to develop chronic canker sores.
Iron deficiency is another common culprit, particularly in women. If your sores keep returning despite good oral care, a simple blood test can check these levels. Correcting a B12 deficiency, for example, often involves daily oral supplements of 1,000 mcg, which can reduce or eliminate recurring outbreaks entirely. Vitamin C deficiency responds to 100 to 500 mg daily for mild cases. These are straightforward fixes that address the root cause rather than just treating symptoms.
Canker Sores vs. Cold Sores
These two get confused constantly, but they’re completely different conditions requiring different treatments. The simplest distinction is location: canker sores occur inside the mouth, while 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. Cold sores are clusters of small, fluid-filled blisters.
Cold sores are caused by the herpes simplex virus and are contagious. Canker sores are not caused by a virus, are not contagious, and their exact cause involves a mix of immune response, stress, minor mouth injuries (like biting your cheek), hormonal changes, and nutritional deficiencies.
Signs a Canker Sore Needs Medical Attention
Most canker sores are a nuisance, not a health threat. But the Cleveland Clinic identifies several situations that warrant a call to your doctor or dentist: sores lasting longer than two weeks, sores larger than about one centimeter (bigger than a pea), sores accompanied by flu-like symptoms, outbreaks recurring two or three times a year, or sores severe enough to interfere with eating, drinking, or daily routines. A sore that won’t heal can occasionally signal something other than a standard canker sore, and it’s worth getting checked.