Most canker sores heal on their own within one to two weeks, but the right combination of rinses, topical treatments, and trigger avoidance can cut down pain significantly and may speed up the process. These small, shallow ulcers form inside the mouth on soft tissue like the inner cheeks, lips, or tongue. They’re not contagious and not caused by a virus, which makes them different from cold sores that appear on the outside border of the lips.
Rinses That Reduce Pain and Promote Healing
The simplest home treatment is a saltwater or baking soda rinse. Dissolve 1 teaspoon of baking soda in half a cup of warm water, swish it around your mouth for 30 seconds, and spit. This shifts the pH inside your mouth toward alkaline, which calms the irritated tissue and creates a less hospitable environment for bacteria. You can repeat this several times a day, especially after meals.
A diluted hydrogen peroxide application also works well. Mix equal parts hydrogen peroxide and water, then dab it directly on the sore with a cotton swab. This disinfects the ulcer surface and helps clear away debris. Avoid swallowing the mixture, and stick to the 1:1 dilution to prevent irritating the surrounding tissue.
Over-the-Counter Gels and Patches
Benzocaine oral gels (sold as Orajel and similar brands) numb the sore on contact, which makes eating and drinking much more manageable. Apply a small amount directly to the ulcer, following the label directions for how often you can reapply. The relief is temporary, usually lasting 30 to 60 minutes, but it’s helpful right before meals.
Adhesive mouth patches are another option. These small discs stick over the sore and form a protective barrier, shielding the ulcer from food, teeth, and tongue contact while delivering a mild antiseptic. They tend to stay in place for a few hours and dissolve on their own.
When a Prescription Helps
For larger or especially painful canker sores, a doctor or dentist can prescribe a steroid dental paste. This type of paste works by suppressing the inflammatory process that keeps the sore swollen and tender. You press a small amount onto the ulcer at bedtime so it stays in contact with the sore overnight. Depending on severity, you may need to apply it two or three times a day, ideally after meals when the area is relatively clean and dry.
Another in-office option is chemical cauterization with silver nitrate. In a randomized trial, 70% of patients treated with a single silver nitrate application had a meaningful drop in pain within one day, compared to just 11% in the placebo group. It doesn’t shorten the overall healing time, but it can make the worst days far more bearable if you’re dealing with a sore that’s interfering with eating or speaking.
Triggers Worth Avoiding
If you get canker sores repeatedly, your toothpaste may be part of the problem. A systematic review found that toothpaste containing sodium lauryl sulfate (SLS), the foaming agent in most commercial toothpastes, was linked to more frequent outbreaks. Switching to an SLS-free toothpaste significantly reduced the number of ulcers, the duration of each episode, and the level of pain. Brands like Sensodyne, Biotene, and Verve are commonly available SLS-free options.
Acidic and abrasive foods are another common trigger. Citrus fruits, tomatoes, pineapple, and crunchy chips or crackers can all irritate the soft tissue inside your mouth and either spark a new sore or aggravate an existing one. While you have an active ulcer, sticking to softer, blander foods makes a noticeable difference in day-to-day comfort.
Nutritional Gaps That Fuel Recurrence
People who get canker sores frequently often have lower intake of certain nutrients. A study comparing people with recurrent canker sores to national dietary data found that those with sores consumed significantly less vitamin B12 and folate. The B12 gap amounted to about 7% less than the recommended daily intake. Previous research has also connected recurrent outbreaks to low iron and zinc levels.
This doesn’t mean a supplement will cure an active sore overnight, but if you notice a pattern of recurring ulcers, it’s worth looking at your diet. Foods rich in B12 (meat, fish, eggs, dairy), folate (leafy greens, beans, fortified grains), and iron (red meat, lentils, spinach) address the most commonly identified gaps. A simple blood test can confirm whether a deficiency is playing a role.
Canker Sores vs. Cold Sores
These two get confused constantly, but they’re completely different conditions. Canker sores appear inside the mouth on soft, non-keratinized tissue like the inner cheeks, lips, and tongue. They have no known single cause and are not contagious. Cold sores (fever blisters) are caused by herpes simplex virus type 1, appear outside the mouth along the border of the lips, and spread easily through direct contact. The treatments are different too: antiviral medications work on cold sores but do nothing for canker sores, and the rinses and pastes described above target canker sores specifically.
Signs a Sore Needs Professional Attention
A canker sore that lasts longer than two weeks is the clearest signal to get it evaluated. Most minor sores resolve well before that mark. You should also pay attention if a sore is unusually large (bigger than about a centimeter across), if you’re developing multiple sores at once in clusters, if you’re running a fever alongside the outbreak, or if the pain is severe enough that you can’t eat or drink adequately. These patterns can sometimes point to an underlying condition that needs a different approach than home care alone.