Most canker sores heal on their own within one to two weeks, but you can speed up the process and reduce pain with the right combination of topical treatments, mouth rinses, and trigger avoidance. The key is starting treatment as early as possible, ideally when you first feel that telltale tingling or spot of tenderness inside your mouth.
What a Canker Sore Actually Is
A canker sore is a small, shallow ulcer that forms inside the mouth, typically on the inner cheeks, lips, tongue, or soft palate. They appear as round white or yellow sores with a red border. Unlike cold sores, which are caused by the herpes virus and appear outside the mouth around the lips, canker sores are not contagious and not caused by an infection you can pass to someone else.
The underlying mechanism involves your immune system attacking the lining of your mouth. Certain immune cells destroy oral tissue, and the process is sustained by a cascade of inflammatory signals. The exact trigger varies from person to person, but the result is the same: a painful open wound on soft tissue that gets irritated every time you eat, drink, or talk.
Topical Treatments That Work Fastest
Over-the-counter gels, pastes, and rinses work best when applied as soon as a sore appears. The most effective OTC options contain one of these active ingredients:
- Benzocaine (found in products like Anbesol, Kank-A, Orabase, and Zilactin-B): a numbing agent that provides immediate pain relief and creates a protective layer over the sore.
- Hydrogen peroxide rinses (like Orajel Antiseptic Mouth Sore Rinse or Peroxyl): these clean the ulcer and reduce bacteria around the wound, which can help it heal faster.
- Protective mouth coatings (like Gelclair): these adhere to the surface of the sore and shield exposed nerve endings, reducing pain while you eat and drink.
Apply these products directly to the sore several times a day, especially before meals. The goal is to keep the ulcer clean, numb the pain, and protect the raw tissue from further irritation.
Simple Mouth Rinses You Can Make at Home
A saltwater rinse is the simplest home remedy. Dissolve about half a teaspoon of salt in a cup of warm water, swish it around your mouth for 30 seconds, and spit. Repeat three or four times a day. The salt draws fluid from the swollen tissue, reducing inflammation and creating a less hospitable environment for bacteria.
Baking soda rinses work similarly. Dissolve a teaspoon of baking soda in half a cup of warm water and rinse the same way. Baking soda neutralizes acids in your mouth that can irritate the sore. You can also make a paste by mixing a small amount of baking soda with water and dabbing it directly on the ulcer, though this will sting briefly.
Foods to Avoid While You’re Healing
Acidic and abrasive foods are the biggest enemies of an open canker sore. While you have an active ulcer, steer clear of citrus fruits and juices (oranges, grapefruits, lemons, limes, pineapple), tomatoes and tomato sauce, coffee, soda, strawberries, and spicy foods. All of these contain acids or irritants that inflame the exposed tissue and can make the sore larger or more painful.
Physically rough foods matter too. Chips, pretzels, crusty bread, and nuts can scrape against the sore and reopen healing tissue. Stick to soft, cool, bland foods until the ulcer closes. Yogurt, smoothies, mashed potatoes, and scrambled eggs are all safe choices that won’t aggravate the wound.
When Sores Keep Coming Back
If you get canker sores regularly, the cause is often something in your daily routine rather than bad luck. Three common culprits are worth investigating.
First, check your toothpaste. Sodium lauryl sulfate (SLS), a foaming agent found in most major toothpaste brands, is a known soft tissue irritant. It’s the same detergent used in shampoos and household cleaners. 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 appear.
Second, look at your nutrient levels. Deficiencies in vitamin B12, folate, and iron are all linked to recurrent mouth ulcers. If you’re getting canker sores frequently and also experience fatigue, a sore or red tongue, or general weakness, a blood test can check for these deficiencies. Correcting them through diet or supplements often reduces outbreaks.
Third, consider stress and sleep. Physical and emotional stress are well-established triggers. Illness, sleep deprivation, and poor diet all put strain on the immune system in ways that can set off the inflammatory response behind canker sores.
Prescription Options for Severe Cases
If OTC treatments aren’t enough, prescription-strength topical steroids can reduce pain and shorten how long sores last. These work by calming the immune response that’s destroying the tissue. They come as gels or pastes applied directly to the ulcer, and commonly prescribed options range from mild to high potency depending on the severity. These steroid treatments don’t cause significant side effects when used in the mouth for short periods, though the sores can still recur.
For widespread ulcers covering a larger area, a prescription steroid mouth rinse can reach sores that are hard to treat with a gel. One potential side effect of steroid rinses is an increased risk of developing a fungal infection in the mouth, so they’re typically used for limited periods.
An antiseptic mouth rinse containing chlorhexidine is another prescription option. It reduces the severity and pain of ulcers, though it doesn’t prevent future outbreaks from happening.
Canker Sores vs. Cold Sores
These two conditions are frequently confused, but they’re completely different. Canker sores form inside the mouth, are not contagious, and have no known single cause. Cold sores (fever blisters) form outside the mouth, usually around the border of the lips, and are caused by the herpes simplex virus. Cold sores appear as clusters of small fluid-filled blisters, while canker sores are single round ulcers. The treatments are entirely different, so getting this distinction right matters.
Signs a Canker Sore Needs Medical Attention
Most canker sores resolve within two weeks without any treatment at all. But certain patterns signal something more serious. Contact your doctor or dentist if a sore lasts longer than two weeks, is larger than a centimeter (roughly the size of a pea), comes with fever or flu-like symptoms, interferes with eating or drinking, or recurs two to three times a year. A sore that won’t heal could indicate an underlying condition that needs evaluation, and persistent ulcers occasionally require a biopsy to rule out other causes.