Most canker sores heal on their own within two weeks, but the right combination of rinses, topical treatments, and trigger avoidance can cut down pain significantly and speed things along. The worst discomfort typically peaks in the first few days, then gradually fades.
Unlike cold sores, which appear on the outside of your lips and are caused by a virus, canker sores form inside your mouth on soft tissue like the inner cheeks, gums, or tongue. They look like small white or yellowish ovals with a red border. Their exact cause isn’t fully understood, but common triggers include mouth injuries (biting your cheek, aggressive brushing), stress, poor sleep, and nutritional gaps.
Rinses That Reduce Pain and Speed Healing
A simple rinse is the fastest thing you can do right now. Dissolve 1 teaspoon of baking soda in half a cup of warm water and swish it around your mouth for 30 seconds, then spit. You can also use a basic salt water rinse at similar proportions. Both options help keep the area clean and create an environment that’s less hospitable to bacteria, which reduces irritation around the sore. Repeat several times a day, especially after meals.
Over-the-counter rinses containing hydrogen peroxide (typically diluted to about 1.5%) work the same way. Look for antiseptic mouth rinses specifically labeled for oral sores. These are widely available at pharmacies and can be alternated with your baking soda or salt water rinse.
Topical Gels and Pastes
For direct pain relief, look for OTC oral gels containing benzocaine. These numb the sore on contact and make eating and drinking far more tolerable. Apply a small amount directly to the sore with a clean finger or cotton swab. The numbing effect is temporary, usually lasting 15 to 30 minutes, so reapply as needed before meals.
Protective oral pastes are another option. These form a barrier over the sore, shielding it from food, drinks, and your teeth. Some combine a numbing agent with a protective coating, which addresses both pain and mechanical irritation at once. Apply these after eating and before bed for the best coverage.
What To Avoid While It Heals
Certain foods will make a canker sore dramatically worse. Acidic items like citrus fruits, tomatoes, and vinegar-based dressings sting on contact and can slow healing. Spicy foods and anything with sharp or rough edges (chips, crusty bread, hard pretzels) physically irritate the ulcer. Stick to softer, blander foods until the sore has closed.
Your toothpaste may also be part of the problem. 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. If you get canker sores regularly, switching to an SLS-free toothpaste is one of the simplest changes you can make. Several brands market themselves specifically as SLS-free, and they’re easy to find online or at most drugstores.
Nutritional Deficiencies That Cause Recurring Sores
If canker sores keep coming back, your diet may be a factor. Deficiencies in iron, vitamin B12, folic acid, and zinc are all linked to recurrent outbreaks. You don’t necessarily need supplements. These nutrients are abundant in leafy greens (folate), red meat and shellfish (iron, B12, zinc), eggs, and fortified cereals. But if you follow a restrictive diet or suspect a deficiency, a simple blood test can confirm whether your levels are low.
This is particularly worth considering if your sores appear in clusters, recur every few weeks, or seem to show up without any obvious trigger like a mouth injury or stressful week.
When a Canker Sore Needs Medical Attention
A typical canker sore is small, painful for a few days, and gone within two weeks. You should pay closer attention if a sore is unusually large (bigger than about a centimeter across), lasts longer than three weeks, keeps coming back before the previous one has healed, or is accompanied by fever. Sores that spread rapidly or make it genuinely difficult to drink fluids also warrant a visit to your doctor or dentist.
For severe or persistent sores, a doctor can prescribe prescription-strength rinses or topical treatments that reduce inflammation more aggressively than anything available over the counter. These are typically reserved for people who get large or frequent outbreaks that interfere with eating and daily life.
Preventing the Next One
Since canker sores don’t have a single identifiable cause, prevention is about managing the web of triggers that contribute to them. Getting enough sleep, eating a nutrient-rich diet, switching to SLS-free toothpaste, and being gentle when you brush all reduce your odds. If you notice sores tend to follow periods of high stress or illness, that pattern itself is useful information. Stress management won’t guarantee you never get another canker sore, but people who get frequent outbreaks often notice a clear connection between their stress levels and flare-ups.
Keeping plaque and tartar buildup under control with regular dental cleanings also helps. A heavy bacterial load in the mouth creates an environment where canker sores are more likely to develop and slower to heal.