Most canker sores heal on their own within 10 days, but the right home treatments can cut pain significantly and speed that timeline. These small, shallow ulcers on the inside of your mouth are not the same as cold sores (which appear on the lips and are caused by a virus). Canker sores are not contagious, and while their exact cause is debated, you have several effective options for treating them at home and preventing them from coming back.
Salt and Baking Soda Rinses
The simplest and cheapest remedy is a rinse you can make right now. Dissolve 1 teaspoon of baking soda in half a cup of warm water, swish it around your mouth for 30 to 60 seconds, and spit it out. A saltwater rinse made the same way works too. Both temporarily raise the pH inside your mouth, creating a less hospitable environment for bacteria and reducing inflammation around the sore. You can do this several times a day, especially after meals.
Topical Honey
Applying a small dab of honey directly to the ulcer is one of the better-studied natural remedies. A systematic review found that honey performed comparably to standard medicated gels for reducing pain and ulcer size in minor canker sores. In studies of more severe oral ulcers (from chemotherapy or radiation), honey groups saw dramatically better outcomes: severe ulcers dropped from 55% to 20% in one trial of pediatric cancer patients, with faster recovery times and less pain across multiple studies.
For a regular canker sore, the practical approach is simple. Apply a small amount of raw honey to the ulcer a few times per day, particularly after eating. It forms a mild protective barrier, has natural antibacterial properties, and tastes far better than most alternatives.
Over-the-Counter Pain Relief
Numbing gels and pastes containing benzocaine are available at any pharmacy and provide temporary relief by dulling the nerve endings around the sore. Look for products labeled specifically for mouth sores and apply them directly to the ulcer with a clean finger or cotton swab. The relief typically lasts 15 to 30 minutes, which can be enough to get through a meal comfortably.
Protective pastes that form a barrier over the sore are another option. These stick to the moist tissue inside your mouth and shield the ulcer from further irritation by food, teeth, or braces. Some combine a numbing agent with the barrier, giving you both protection and pain relief.
Alum Powder
Alum powder (potassium aluminum sulfate), found in the spice aisle of most grocery stores, is a traditional remedy that has some science behind it. It works as an astringent, contracting the tissue and precipitating proteins on the surface of the ulcer. This essentially creates a clean wound bed and promotes faster healing. It also has antibacterial and mild anti-inflammatory effects. The FDA recognizes alum as generally safe for consumer use.
To use it, mix a tiny pinch of alum powder with a drop of water to form a paste, apply it directly to the sore, let it sit for about a minute, then rinse your mouth. It will sting and taste unpleasant, but many people report the sore feels noticeably better afterward.
What to Avoid While You Have One
Acidic foods like citrus fruits, tomatoes, and vinegar-based dressings will make the pain significantly worse and can irritate the tissue further. Spicy foods, crunchy chips, and hard bread edges are also common culprits for re-aggravating a healing sore. Stick to softer, blander foods until it closes up. If you drink coffee or eat something acidic, follow it with a water rinse.
When Healing Takes Longer
Not all canker sores are the same. Minor canker sores, the most common type, are smaller than a centimeter across and heal in about 10 days without scarring. Major canker sores are larger, deeper, and can take weeks to months to fully resolve. They sometimes leave scars. A third type, called herpetiform canker sores, appears as clusters of tiny ulcers that merge into larger ones and typically heal within two weeks.
If you have a sore that lasts longer than two weeks or is larger than a pea (roughly one centimeter), those are the standard thresholds for getting it evaluated. Persistent or unusually large ulcers can occasionally signal an underlying condition that needs attention.
Prescription Treatments for Severe Cases
For canker sores that are large, extremely painful, or keep recurring, a doctor or dentist can prescribe a steroid-based mouth rinse. These prescription rinses reduce inflammation directly at the ulcer site. You swish the liquid for about a minute after meals and before bed, then spit it out. They are typically used for a limited course and are reserved for sores that don’t respond to simpler treatments.
Preventing Canker Sores From Recurring
If you get canker sores frequently, your toothpaste may be part of the problem. Most mainstream toothpastes contain sodium lauryl sulfate (SLS), a foaming agent that can irritate the soft tissue in your mouth. A systematic review found that switching to an SLS-free toothpaste significantly reduced the number of ulcers, how long they lasted, the number of outbreaks, and how much they hurt. One study within that review found ulcer counts dropped from an average of 14.3 to 5.1 after participants switched to SLS-free toothpaste. Several brands market themselves as SLS-free, and they are easy to find online or in health food stores.
Nutritional deficiencies also play a role. Low levels of iron, vitamin B12, folic acid, and zinc are all linked to recurrent canker sores. If you get them often and can’t identify an obvious trigger, it is worth looking at your diet or asking about a blood test to check for deficiencies. Leafy greens, legumes, fortified cereals, and lean meats cover most of these nutrients.
Other common triggers include stress, mouth injuries from biting your cheek or aggressive brushing, and hormonal changes. Braces and ill-fitting dental appliances are frequent offenders too. Using orthodontic wax over sharp edges can prevent the mechanical irritation that starts many sores in the first place.