Most canker sores heal on their own within two weeks, but you can speed things up and cut the pain significantly with a few simple treatments. These small, round ulcers appear inside the mouth, typically on the inner cheeks, tongue, or soft palate, and they tend to hurt most during the first few days.
Saltwater and Hydrogen Peroxide Rinses
The simplest and cheapest remedy is a saltwater rinse. Dissolve half a teaspoon of table salt in a glass of lukewarm water, swish it around your mouth for 30 seconds, and spit. Do this a few times a day, especially after meals. It eases discomfort and helps the tissue heal faster. The rinse won’t sting as badly as you’d expect, and it works by drawing fluid out of the swollen tissue to reduce inflammation.
A diluted hydrogen peroxide rinse (equal parts 3% hydrogen peroxide and water) is another option. Dab it directly on the sore with a cotton swab or swish gently. This cleans the ulcer surface and can prevent secondary irritation from bacteria. Don’t swallow the solution.
Over-the-Counter Pain Relief
Topical gels and pastes containing benzocaine numb the sore on contact and create a protective film over it. Apply them directly to the ulcer as soon as you notice it forming. The earlier you start, the more effective they are at both reducing pain and shortening healing time. You’ll find these at any pharmacy, usually labeled for mouth sores or oral pain.
If you prefer something more natural, dabbing a small amount of honey on the sore three times a day has shown real results in clinical trials. Honey reduces ulcer size and pain, likely because of its anti-inflammatory and antimicrobial properties. Plain, unprocessed honey works best. Apply it after meals and try not to eat or drink for a few minutes afterward so it stays in contact with the sore.
What to Avoid While Healing
Acidic foods like tomatoes, citrus fruits, and vinegar-based dressings will make a canker sore burn. So will spicy food, salty chips, and anything with rough edges like toast or hard pretzels. Stick with softer, blander foods until the sore closes up. Brushing with a soft-bristled toothbrush helps too. Some people find that toothpaste containing sodium lauryl sulfate (a foaming agent) triggers canker sores or worsens existing ones, so switching to an SLS-free toothpaste is worth trying if you get them often.
Prescription Treatments
For sores that are especially large or painful, a dentist or doctor can prescribe a corticosteroid dental paste. You press a small dab (about a quarter inch) onto the sore and let a thin film develop over it. The key is not to rub it in. Just press gently and let it sit. Applying it at bedtime keeps the medication in contact with the ulcer overnight, and during the day you can reapply after meals if needed.
Another in-office option is chemical cauterization with silver nitrate. A dentist applies it directly to the sore, which essentially burns the nerve endings on the surface. It doesn’t necessarily make the ulcer heal faster, but it usually eliminates the pain almost immediately. One application is often enough.
When Canker Sores Keep Coming Back
If you get canker sores repeatedly, a nutritional deficiency may be the underlying cause. The nutrients most commonly linked to recurrent canker sores are vitamin B12, iron, zinc, and folate. B12 and iron deficiencies are particularly common culprits. A simple blood test can identify whether you’re low in any of these, and correcting the deficiency through diet or supplements often reduces how frequently the sores appear.
Stress is another well-known trigger. Many people notice canker sores popping up during exam weeks, after poor sleep, or during emotionally difficult periods. You can’t always control stress, but recognizing the pattern helps you start treatment earlier and avoid irritating foods before the sore gets worse.
Canker Sores vs. Cold Sores
These two get confused constantly, but the distinction is straightforward. Canker sores appear inside the mouth and look like a single round white or yellow sore with a red border. Cold sores (fever blisters) appear outside the mouth, usually around the border of the lips, and look like 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 and cannot spread to other people.
How Long Healing Takes
Most canker sores are the minor type, measuring less than 5 millimeters across. These heal within one to two weeks without scarring. The pain typically peaks in the first three to four days and then gradually fades as the ulcer closes.
Major canker sores, which make up about 10% of cases, are larger than 10 millimeters and can last 5 to 10 weeks. These deeper ulcers tend to appear on the lips, soft palate, or throat, and they may leave scars. Fever, difficulty swallowing, and general fatigue can accompany them. If a canker sore is unusually large, lasts longer than two weeks, or comes with a fever, it’s worth having a specialist evaluate it. Persistent or severe recurring sores can sometimes signal an underlying condition that needs its own treatment.