Most canker sores heal on their own within 10 to 14 days, but you can speed that timeline up and reduce pain significantly with the right approach. The key is treating them early, avoiding things that irritate them, and knowing when a sore needs more than home care.
What You’re Dealing With
Canker sores (aphthous ulcers) are small, shallow ulcers that form inside the mouth, on the tongue, inner cheeks, gums, or soft palate. They typically appear as a single round white or yellow sore with a red border. They’re not the same as cold sores, which are clusters of small fluid-filled blisters that show up outside the mouth, usually along the lip border. Canker sores aren’t contagious.
Most canker sores are the “minor” type, under a centimeter across, and heal within two weeks without scarring. Major canker sores are larger, deeper, and can take up to six weeks to heal, sometimes leaving a scar. If you’ve never had one this severe before, it’s worth getting it checked.
Start Treatment as Soon as You Notice It
The single most important thing you can do is act fast. Over-the-counter gels, pastes, and liquids work best when applied as soon as the sore appears. The active ingredients to look for fall into a few categories:
- Benzocaine (found in products like Anbesol and Zilactin-B) numbs the area and provides immediate pain relief.
- Hydrogen peroxide rinses (like Orajel Antiseptic Mouth Sore Rinse) clean the sore and reduce bacteria around it.
- Fluocinonide is a prescription-strength anti-inflammatory cream that your dentist or doctor can prescribe for more stubborn sores.
Apply these directly to the sore, not as a general mouth rinse. A paste or gel tends to stick better than a liquid and keeps the active ingredient in contact with the ulcer longer. Reapply after eating or drinking.
Simple Rinses That Help
A saltwater rinse is the oldest and simplest remedy for a reason. Dissolve about half a teaspoon of salt in a cup of warm water, swish it around for 30 seconds, and spit. Do this a few times a day, especially after meals. The salt draws fluid out of the inflamed tissue, which can reduce swelling and discomfort.
Baking soda rinses work similarly. Use the same ratio: about half a teaspoon in a cup of water. Baking soda helps neutralize acids in the mouth that irritate the open sore. You can alternate between salt and baking soda rinses throughout the day. Neither will sting as badly as you might expect, though the first few seconds of contact can be uncomfortable.
What to Eat and What to Avoid
Certain foods both trigger new canker sores and make existing ones worse. While the sore is active, steer clear of acidic foods (tomatoes, citrus fruits, pineapple), spicy dishes, salty snacks, and anything with sharp edges like chips or crusty bread. Coffee and carbonated drinks can also irritate the area.
If you get canker sores repeatedly, pay attention to whether specific foods seem to set them off. Common triggers beyond the obvious acidic and spicy categories include cheese, eggs, peanuts, and almonds. Everyone’s trigger list is a bit different, so tracking what you ate in the day or two before an outbreak can reveal patterns over time.
Stick with soft, cool, or room-temperature foods while you’re healing. Yogurt, smoothies, oatmeal, and mashed potatoes are all easy choices that won’t aggravate the sore.
Nutritional Deficiencies Worth Checking
If canker sores keep coming back, a nutritional gap could be the underlying cause. Vitamin B12 deficiency is the most commonly linked, and it makes sense: B12 supports red blood cell production and tissue repair, so when levels drop, mouth tissues heal poorly and ulcers recur. Folic acid (B9) plays a similar role in cell growth and repair, and low levels can trigger oral inflammation.
Iron deficiency reduces oxygen supply to tissues throughout the mouth, making soreness and ulcers more likely. Zinc deficiency delays wound healing and weakens the immune response, increasing how often sores appear and how long they stick around. If you’re dealing with canker sores more than a few times a year, a blood test to check these levels is a practical next step. Supplementation can make a real difference, but it’s most effective when you know which specific deficiency you’re correcting rather than guessing.
When a Canker Sore Needs Professional Treatment
The American Academy of Oral Medicine recommends that any mouth ulcer lasting more than 10 to 14 days be evaluated by a dentist, and biopsied if necessary. Canker sores can sometimes be confused with other conditions that look similar, so persistent sores shouldn’t be ignored.
Four or more canker sores per year with noticeable symptoms is classified as moderate disease, and professional care is recommended. For recurring or severe cases, your doctor or dentist has options that aren’t available over the counter. Prescription steroid mouth rinses containing dexamethasone reduce inflammation across multiple sores at once. Lidocaine rinses can numb pain broadly when sores are in hard-to-reach spots.
For individual stubborn sores, chemical cauterization is an option. A product called Debacterol chemically seals the sore and can reduce healing time to about a week. Silver nitrate cautery has stronger evidence behind it: in one clinical study, 60% of patients treated with silver nitrate had fully healed ulcers by day seven, compared to 32% in the control group. The treated group’s average healing time was 2.7 days after the procedure, versus 5.5 days without it. Pain relief was significant starting from the first day. The procedure itself takes seconds and is done in a dental or medical office.
Reducing Your Risk of Future Sores
Mechanical irritation is one of the most controllable triggers. A sharp tooth edge, ill-fitting braces, or aggressive brushing can all create the small injuries that become canker sores. Use a soft-bristled toothbrush and brush gently, especially along the gums and inner cheeks.
You may have heard that switching to a toothpaste without sodium lauryl sulfate (SLS), the foaming agent in most toothpastes, can prevent outbreaks. The evidence on this is mixed. SLS can irritate the skin and mucous membranes, which makes the theory plausible, but a 2019 review found there wasn’t enough data to confirm that SLS-free toothpastes actually reduce ulcer frequency, duration, or pain. That said, if your mouth generally feels irritated after brushing, trying an SLS-free option is low-risk and inexpensive.
Stress is another well-established trigger. Canker sores often show up during high-pressure periods, and while “reduce stress” is easier said than done, recognizing the pattern can at least help you start treatment earlier. Keep your preferred OTC treatment on hand so you can apply it at the first sign of tingling or soreness, before the ulcer fully forms. Early treatment consistently leads to shorter, less painful outbreaks.