Most canker sores heal on their own within a few weeks, but the pain peaks in the first several days, and that’s usually what sends people searching for relief. The good news: a combination of simple rinses, over-the-counter products, and trigger avoidance can cut pain significantly and may speed healing.
Salt Water and Baking Soda Rinses
The simplest remedy is one you can make in your kitchen right now. Dissolve about half a teaspoon of salt in a cup of warm water, swish gently for 15 to 30 seconds, and spit. You can do this several times a day, especially after meals. Salt water draws fluid out of the inflamed tissue, temporarily reducing swelling and the pain that comes with it.
Baking soda works similarly. Mix about a teaspoon into half a cup of warm water and rinse. Baking soda is mildly alkaline, which helps neutralize acids in the mouth that irritate the open sore. Some people alternate between salt and baking soda rinses throughout the day. Neither will sting as badly as you might expect, though the first few seconds on a raw sore can be uncomfortable.
Over-the-Counter Numbing Products
If rinsing alone isn’t enough, topical products containing benzocaine (sold as Anbesol, Orabase, Zilactin-B, and others) create a temporary numbing film over the sore. You apply them directly to the ulcer with a clean finger or cotton swab. The relief is almost immediate but wears off within an hour or so, making reapplication necessary before meals or whenever pain flares.
Hydrogen peroxide rinses, like Orajel Antiseptic Mouth Sore Rinse, take a different approach. They clean the sore and reduce bacteria around it, which can help prevent secondary irritation. Dilute hydrogen peroxide to half strength with water if using it straight from the bottle, and avoid swallowing it.
Prescription Options for Severe Sores
When a canker sore is larger than a centimeter (roughly the size of a pea or bigger), it falls into the “major” category and can take months to heal, often leaving a scar. For sores this severe, or for frequent outbreaks, a doctor or dentist can prescribe stronger treatments.
Fluocinonide is a prescription-strength anti-inflammatory gel applied directly to the sore. For people dealing with multiple sores at once, a medicated mouth rinse containing a steroid or a numbing agent like lidocaine can coat all the affected areas at once. Another option is chemical cautery with a product called Debacterol, which essentially seals the sore and may reduce healing time to about a week. Silver nitrate cautery is sometimes used as well. It hasn’t been shown to speed healing, but it can relieve pain.
Switch Your Toothpaste
One of the most overlooked causes of recurring canker sores is sodium lauryl sulfate, or SLS, a foaming agent in most mainstream toothpastes. SLS strips away the protective mucus layer inside your mouth, leaving the tissue underneath more vulnerable to damage and ulceration.
In one widely cited study, patients with recurrent canker sores averaged 14.3 ulcers over three months while using an SLS toothpaste. After switching to an SLS-free version, that number dropped to 5.1, a 64% reduction. Most people notice a meaningful difference within four to eight weeks of making the switch. SLS-free toothpastes are easy to find now. Brands like Sensodyne, Tom’s of Maine (some formulas), and Biotene all make versions without it. Check the ingredient list for “sodium lauryl sulfate” near the top.
Check for Nutritional Deficiencies
If you get canker sores repeatedly, the problem may not be in your mouth at all. Vitamin B12 deficiency has a well-documented connection to recurrent canker sores. In screening studies, roughly 18% of patients with recurring outbreaks turned out to be B12 deficient. Research published in the Journal of Indian Academy of Oral Medicine and Radiology found a statistically significant relationship between low B12 levels and recurrent sores, and patients who received B12 replacement therapy often saw a dramatic improvement.
Iron and folate deficiencies have also been linked to frequent outbreaks, though B12 shows the strongest correlation. If you’re getting canker sores more than a few times a year, it’s worth asking for a blood test rather than just treating symptoms with multivitamins. Knowing the specific deficiency lets you target the right supplement.
Avoid Common Triggers
While you’re healing, certain foods will make a canker sore dramatically worse. Citrus fruits, tomatoes, vinegar-based dressings, and anything with sharp edges (chips, crusty bread, pretzels) can reopen or irritate the wound. Spicy food and very hot drinks are also worth avoiding until the sore closes.
Beyond food, pay attention to physical trauma. Biting the inside of your cheek, aggressive brushing, and orthodontic wires rubbing against tissue are common triggers. If braces or a dental appliance is causing repeated sores in the same spot, dental wax can create a buffer. Using a soft-bristled toothbrush and brushing gently around the sore helps prevent further damage to the area.
Stress is another well-known trigger, though harder to control. Outbreaks often cluster around periods of high stress or poor sleep, likely because the immune system’s inflammatory response becomes less regulated.
Low-Level Laser Treatment
For people with frequent or particularly painful canker sores, low-level laser therapy is an option some dental offices now offer. A single 30-second exposure to red laser light at 680 nanometers has been shown to eliminate pain within 24 hours in over 73% of patients, with more than 90% reporting complete comfort by the following day. By comparison, untreated sores typically cause pain for at least five days.
The treated sores also healed to a comfortable, closed state within about two days, roughly two to six times faster than untreated ones. The treatment itself is painless and takes seconds. Not every dental office offers it, but it’s worth asking about if you deal with canker sores regularly.
What the Healing Timeline Looks Like
Minor canker sores, the kind most people get, are smaller than a centimeter across. Pain typically improves within a few days and the sore itself heals within one to two weeks without leaving a scar. The worst discomfort is usually concentrated in the first two to four days after the sore appears.
Major canker sores are larger, deeper, and significantly more painful. These can persist for weeks to months and often leave scarring. A third, less common type called herpetiform canker sores appears as clusters of tiny ulcers that may merge together. Despite the name, these have nothing to do with the herpes virus. If a sore hasn’t started improving after two weeks, is unusually large, keeps coming back, or is accompanied by fever, it’s worth getting evaluated to rule out other conditions.