Most canker sores heal on their own within one to two weeks, but you can speed that up and reduce pain significantly with the right approach. The key is starting treatment early, ideally as soon as you feel that familiar tingling or spot of tenderness inside your mouth.
What a Canker Sore Actually Is
A canker sore is a small, round ulcer that forms inside your mouth, usually on the inner cheeks, lips, or tongue. It typically appears as a white or yellow spot with a red border. Unlike cold sores, canker sores are not caused by a virus and are not contagious. They form when your immune system essentially overreacts, sending inflammatory cells that destroy a small patch of the tissue lining your mouth.
The exact cause isn’t fully understood, but common triggers include minor mouth injuries (biting your cheek, sharp food, dental work), stress, hormonal changes, and deficiencies in iron, folate, or vitamin B12. Some people get them once or twice a year. Others deal with recurring cycles.
Home Remedies That Actually Help
A saltwater or baking soda rinse is the simplest and most accessible treatment. Mix about half a teaspoon of salt or baking soda into a cup of warm water and swish for 30 to 60 seconds. The solution reduces acid levels in your mouth, which lowers irritation around the ulcer and creates a less hospitable environment for bacteria. You can do this several times a day, especially after meals.
Applying a small amount of milk of magnesia directly to the sore with a cotton swab works on a similar principle, neutralizing acid right at the surface. Placing a damp tea bag (black tea) against the sore can also provide temporary relief, since the tannins have mild astringent properties. Ice chips held against the sore numb the area and reduce inflammation in the short term.
The most important home care step is avoiding foods that aggravate the sore. Citrus, tomatoes, spicy dishes, and crunchy or sharp-edged foods like chips and crusty bread will all make the pain worse and can delay healing.
Over-the-Counter Products Worth Trying
If home rinses aren’t enough, several pharmacy products can meaningfully reduce pain and shorten healing time. The most effective ones come as pastes, gels, or liquids that you apply directly to the sore. Look for products containing benzocaine, which is a topical numbing agent found in brands like Anbesol, Orabase, and Zilactin-B. These provide near-instant pain relief that lasts 30 minutes to an hour.
Hydrogen peroxide rinses designed for mouth sores (like Orajel Antiseptic Mouth Sore Rinse) help keep the area clean and reduce bacterial buildup. You can also make your own by mixing equal parts 3% hydrogen peroxide and water, dabbing it on the sore with a cotton swab. Don’t swallow it.
For the best results, apply these products as soon as you notice a sore forming. The earlier you start, the more you can limit its size and duration.
When You Need Something Stronger
If you get canker sores frequently or have one that’s unusually large and painful, a dentist or doctor can prescribe stronger options. Prescription-strength steroid rinses reduce the immune response that’s driving the ulcer, which can dramatically cut healing time. Steroid ointments applied directly to the sore work on the same principle but stay in contact with the tissue longer.
Laser treatment is another option that’s becoming more widely available at dental offices. In one controlled study, patients treated with a diode laser experienced near-complete pain relief immediately after the session. Their sores healed in about 3 days on average, compared to nearly 9 days in the untreated group. The procedure takes just a few minutes and doesn’t require anesthesia.
Preventing Canker Sores From Coming Back
If you’re someone who gets canker sores regularly, one of the simplest changes you can make is switching to a toothpaste that doesn’t contain sodium lauryl sulfate (SLS). SLS is a foaming agent found in most mainstream toothpastes, and it irritates the delicate tissue inside your mouth. A systematic review of clinical trials found that people using SLS-free toothpaste developed significantly fewer ulcers, had shorter outbreaks (roughly two fewer days per episode), and experienced less pain overall. Brands like Sensodyne, Biotene, and some Tom’s of Maine varieties are SLS-free.
Beyond toothpaste, pay attention to patterns. Keep a rough mental note of what you ate, how stressed you were, or whether you injured your mouth before an outbreak. Some people find that certain foods, particularly nuts, chocolate, or acidic fruits, reliably trigger sores. If your canker sores coincide with periods of poor diet or fatigue, it may be worth having your doctor check your iron, folate, and B12 levels, since deficiencies in all three are linked to recurrent outbreaks.
Canker Sores vs. Cold Sores
These two get confused constantly, but they’re completely different. Canker sores appear inside the mouth and are not caused by a virus. Cold sores (fever blisters) appear on the outside of the mouth, usually on or around the lips, and are caused by herpes simplex virus type 1. Cold sores look like clusters of small, fluid-filled blisters. Canker sores are single, open ulcers with a white or yellow center. Cold sores are contagious; canker sores are not.
This distinction matters because the treatments are different. Antiviral medications work on cold sores but do nothing for canker sores.
Signs a Sore Needs Medical Attention
Most canker sores are minor and resolve within two weeks. Major canker sores, which are larger than about a centimeter across, can take weeks or even months to heal and sometimes leave scars. A third type, called herpetiform canker sores, appears as clusters of tiny ulcers that typically heal within about two weeks.
Any sore inside your mouth that hasn’t healed after two weeks deserves a professional look. A persistent sore that doesn’t follow the normal healing pattern can occasionally signal something more serious, including oral cancer, which can appear as a white or reddish patch, a non-healing ulcer, or a lump inside the mouth. Other warning signs include unexplained loose teeth, ear pain, and difficulty swallowing. The two-week mark is the standard threshold that doctors and dentists use to decide whether further evaluation is needed.