Most canker sores heal on their own within one to two weeks, but you can speed up the process and cut the pain significantly with the right combination of rinses, topical treatments, and trigger avoidance. The key is starting treatment early, ideally within the first day or two of noticing the sore.
What’s Actually Happening Inside the Sore
Canker sores (aphthous ulcers) are not infections. They’re the result of your immune system attacking the thin tissue lining your mouth. Specific immune cells called cytotoxic T cells destroy patches of oral tissue, creating the shallow, painful craters you see on your inner cheeks, lips, tongue, or the floor of your mouth. Elevated levels of inflammatory signaling molecules drive the process, which is why canker sores tend to flare during periods of stress, illness, or nutritional depletion.
Because they’re immune-driven rather than caused by a virus or bacteria, canker sores aren’t contagious. This also means antibiotics won’t help. Treatments that work target either pain relief or the inflammatory response itself.
Salt Water and Baking Soda Rinses
A simple rinse is the fastest thing you can do right now. Mix 1 teaspoon of salt and 1 teaspoon of baking soda into 4 cups (1 quart) of water. Swish gently for 30 seconds and spit. You can also use salt or baking soda alone in the same ratio. Repeat every 4 to 6 hours throughout the day.
Salt water draws fluid from the inflamed tissue, reducing swelling. Baking soda neutralizes acids in your mouth that irritate the open sore. Neither will sting as much as you’d expect if you keep the concentration low, which is why the 1-teaspoon-per-quart ratio matters. Using too much salt creates a hypertonic solution that burns.
Over-the-Counter Topical Treatments
Benzocaine gels and ointments at 20% concentration are the most widely available option for numbing the pain. You apply a small amount directly to the sore before meals or whenever pain flares. The numbing effect lasts 15 to 30 minutes, enough to get through eating comfortably.
Protective pastes that contain ingredients like carboxymethylcellulose form a barrier film over the sore, shielding it from food, drinks, and your teeth. These work best when applied to a dry sore surface, so blot the area with a tissue first. Some products combine a numbing agent with a protective base, which gives you both pain relief and physical coverage.
Hydrogen peroxide rinses (diluted to the concentration on the label, usually around 1.5%) can also help keep the area clean and reduce bacterial buildup around the ulcer. Don’t swallow the rinse.
Honey as a Home Remedy
Applying raw honey directly to a canker sore three times daily has shown results comparable to over-the-counter medicated gels for both pain and ulcer size. A clinical trial comparing honey to a standard salicylate gel over five days found no significant difference in outcomes between the two groups, with both showing improvement in pain scores and sore size. Honey’s natural anti-inflammatory and wound-healing properties make it a reasonable option if you don’t have a pharmacy product on hand. Dab a small amount on the sore after meals and before bed.
Switch to SLS-Free Toothpaste
Sodium lauryl sulfate (SLS) is a foaming agent in most toothpastes, and it’s a well-documented trigger for canker sores. A meta-analysis of four clinical trials found that switching to an SLS-free toothpaste reduced the number of ulcers by a statistically significant margin. In a pooled analysis of 101 participants, those using SLS-free toothpaste developed roughly four fewer ulcers over the study period compared to those using standard toothpaste.
If you get canker sores more than a few times a year, this is one of the simplest long-term changes you can make. SLS-free options are available at most drugstores. Check the ingredients list for “sodium lauryl sulfate” and avoid it.
Check for Nutritional Deficiencies
Recurring canker sores have a strong link to low levels of vitamin B12, folate, and iron. In one study of patients with recurrent mouth ulcers, over 50% were deficient in B12 and nearly 46% had low folate levels. None of the healthy controls in that study were B12 deficient.
If your sores keep coming back, it’s worth asking your doctor to check these levels with a simple blood test. Correcting a deficiency through diet or supplements can dramatically reduce how often sores appear. Good dietary sources of B12 include meat, fish, eggs, and fortified cereals. Folate is abundant in leafy greens, beans, and citrus. Iron comes from red meat, lentils, and spinach.
Prescription Options for Severe Sores
When canker sores are large (over 1 centimeter), deep, or keep recurring in clusters, prescription-strength treatments can make a real difference. Steroid mouthwashes reduce the inflammatory immune response that’s destroying your mouth tissue. You swish the liquid for a set period and spit it out, typically several times a day. These work best when started at the very first sign of a sore forming.
Prescription steroid pastes applied directly to the sore are another option for isolated ulcers. Your doctor or dentist can determine which approach fits based on the size, number, and frequency of your sores. Major aphthous ulcers, which are larger and involve deeper tissue damage, sometimes take weeks to heal without prescription intervention.
Common Triggers to Avoid
While you’re healing, certain foods and habits will make the sore worse or slow recovery:
- Acidic foods like tomatoes, citrus fruits, and vinegar-based dressings directly irritate open tissue.
- Spicy foods containing capsaicin or hot spices cause immediate pain and can prolong inflammation.
- Crunchy or sharp foods like chips, crusty bread, and pretzels can physically reinjure the sore.
- Dental hardware including braces, retainers, or rough tooth edges that rub against the same spot repeatedly. Orthodontic wax can cover the offending bracket or wire.
Stress is another consistent trigger. It shifts immune function in ways that promote the inflammatory T-cell activity behind canker sores. You can’t always eliminate stress, but recognizing the pattern helps you start treatment earlier when you know a flare is likely.
Signs a Sore Needs Professional Attention
Most canker sores resolve without complications, but certain patterns warrant a visit to your doctor or dentist. The Mayo Clinic flags these specific red flags: sores lasting longer than two weeks, unusually large ulcers, new sores developing before old ones finish healing, sores extending onto the outer lip border, pain you can’t manage with over-the-counter treatments, difficulty eating or drinking, and high fever accompanying the sores. A sore that won’t heal could indicate something other than a simple canker sore, including conditions that look similar but require different treatment.