Most canker sores heal on their own within one to two weeks, but the right treatment can cut that time significantly and reduce pain in the meantime. About 21% of people who treat canker sores early see complete healing within three days, compared to only 8% of those who leave them alone. The key is acting fast, ideally as soon as you feel that telltale tingling or spot the sore forming.
Start With a Simple Rinse
The easiest first step is a saltwater or baking soda rinse. Mix about half a teaspoon of salt (or baking soda) into a cup of warm water, swish it around your mouth for 30 seconds, and spit. Do this several times a day, especially after meals. Salt draws fluid out of the sore, which reduces swelling, while baking soda helps neutralize acids in your mouth that irritate the ulcer. Neither will sting as badly as you might expect, and both create a less hospitable environment for bacteria that can slow healing.
Over-the-Counter Treatments That Work
If a rinse isn’t enough, topical products with numbing agents provide real relief. Look for gels or pastes containing benzocaine, sold under names like Anbesol, Orabase, and Zilactin-B. These numb the sore on contact, making it easier to eat and talk. Apply them directly to the sore with a clean finger or cotton swab, and reapply as directed on the label.
Hydrogen peroxide rinses (like Orajel Antiseptic Mouth Sore Rinse) are another option. You can also make your own by mixing equal parts water and hydrogen peroxide, dabbing it onto the sore with a cotton swab, then following up with a small dab of milk of magnesia. Just be careful not to swallow the peroxide. The peroxide cleans the ulcer surface while the milk of magnesia coats it, creating a protective barrier.
Alcohol-free mouth rinses can also help keep the area clean without the burning sting that alcohol-based products cause on open sores.
What to Avoid While It Heals
What you don’t put in your mouth matters as much as what you do. Acidic foods like tomatoes, citrus fruits, and vinegar-based dressings will aggravate the sore and can extend healing time. Spicy foods, crunchy chips, and hard pretzels cause direct physical irritation. Stick to softer, blander foods until the sore closes up. Drinking through a straw can help liquids bypass the sore if it’s in an inconvenient spot.
Avoid toothpaste containing sodium lauryl sulfate (SLS), a foaming agent that irritates oral tissue. Many people who switch to an SLS-free toothpaste notice fewer recurrences.
When Sores Keep Coming Back
Occasional canker sores are normal, but if you get them frequently, a nutritional deficiency may be involved. One study found that over 50% of people with recurrent canker sores were deficient in vitamin B12, compared to none in the control group. When those patients received B12 supplementation, 73% recovered completely. Iron deficiency has also been linked to recurrent sores, and about 70% of patients improved with iron and other nutritional supplementation.
If you’re getting canker sores regularly, it’s worth looking at your diet. Foods rich in B12 include meat, fish, eggs, and dairy. Folate comes from leafy greens, beans, and fortified grains. Iron is found in red meat, lentils, and spinach. A simple blood test can identify whether you’re low in any of these nutrients.
Stress is another well-known trigger. Canker sores involve an overactive immune response in the mouth’s soft tissue, where the body essentially attacks its own lining. Stress amplifies this response. Physical trauma to the mouth, like biting your cheek, aggressive brushing, or dental work, can also set one off. Once a site in your mouth has been injured and healed, that spot becomes more vulnerable to future sores when you’re run down or stressed.
Prescription Options for Severe Sores
For large or especially painful sores that don’t respond to over-the-counter products, a doctor or dentist can prescribe stronger treatments. Prescription-strength topical steroids (like fluocinonide) reduce inflammation and speed healing more aggressively than anything available on the shelf. These are applied directly to the sore as a paste or gel.
Chemical cauterization is another option your dentist may offer. This involves applying a chemical agent directly to the sore to destroy the damaged tissue and seal the surface. It sounds harsh, but it can dramatically reduce pain almost immediately and shorten healing time. The initial application stings briefly, but the relief afterward is significant.
For people with frequent, severe outbreaks, doctors sometimes prescribe oral medications that suppress the immune response driving the ulcers. These are reserved for cases where sores are large, numerous, or constant enough to interfere with eating and daily life.
Canker Sores vs. Cold Sores
Canker sores form inside the mouth, on soft tissue like the inner cheeks, gums, tongue, or soft palate. They are not contagious and are not caused by a virus. Cold sores, by contrast, appear on or around the lips, are caused by the herpes simplex virus, and are highly contagious. If your sore is on the outside of your mouth or on the border of your lip, it’s likely a cold sore and requires antiviral treatment instead.
A canker sore that hasn’t healed after three weeks, keeps growing larger, or is accompanied by a high fever warrants professional evaluation. Unusually large sores (bigger than about a centimeter across) or sores that spread in clusters can sometimes signal an underlying condition that needs attention beyond home treatment.