Most canker sores heal on their own within a few weeks, but the right combination of pain relief and protective treatments can shorten that timeline and make the wait far more bearable. These small, painful white or yellow ulcers form inside the mouth, on the inner cheeks, lips, or tongue, and they respond well to both over-the-counter products and simple home remedies.
Why Canker Sores Form
Canker sores develop when your immune system mistakenly attacks the cells lining the inside of your mouth. In people who are prone to them, an inflammatory chain reaction drives immune cells to destroy small patches of tissue, leaving behind an open ulcer. Common triggers include minor mouth injuries (biting your cheek, aggressive brushing, dental work), stress, hormonal shifts, acidic or spicy foods, and nutritional deficiencies in iron, zinc, folate, or vitamin B12.
They are not the same thing as cold sores. Cold sores are fluid-filled blisters caused by a virus that appear outside the mouth, typically around the border of the lips. Canker sores are not contagious and only form inside the mouth.
How Long They Last
Minor canker sores, the most common type, are smaller than a centimeter across (roughly the size of a pea) and heal within a few weeks without scarring. Major canker sores are larger than one centimeter, significantly more painful, and can take months to heal. They often leave scars. If your sore is unusually large, lasts longer than three weeks, or keeps coming back in clusters, it’s worth having a dentist or doctor take a look.
Salt Water and Baking Soda Rinses
A simple rinse is one of the fastest things you can do at home. Mix 1 teaspoon of salt and 1 teaspoon of baking soda into 1 quart (4 cups) of water. Swish a mouthful gently over the sore for 30 seconds, then spit. You can do this several times a day, especially after meals. The salt draws fluid from the inflamed tissue to reduce swelling, while the baking soda creates a mildly alkaline environment that helps keep bacteria in check and soothes irritation.
If you find the quart ratio too mild, some people prefer a more concentrated version: half a teaspoon of salt in a single cup of warm water. It will sting more but delivers a stronger effect. Use whichever concentration you can tolerate comfortably.
Over-the-Counter Pain Relief
Benzocaine gels, sprays, and ointments are the most widely available topical numbing agents for canker sores. Apply a small amount directly to the sore up to four times a day. The numbness kicks in within a minute or two and typically lasts long enough to eat or drink without wincing. Benzocaine products are safe for adults and children 2 and older, but should not be used on children under 2.
Benzocaine lozenges work similarly. Dissolve one slowly in your mouth every two hours as needed. These are better suited for sores on the tongue or deeper in the mouth where a gel is hard to keep in place.
Beyond numbing agents, look for products containing a protective coating ingredient. Several OTC oral pastes form a thin barrier over the ulcer, shielding it from food, drinks, and friction so it can heal faster. Brands marketed specifically for canker sores (like Orajel or Kank-A) combine numbing with this protective effect.
Hydrogen Peroxide as a Rinse
Diluted hydrogen peroxide can help clean the sore and reduce bacteria around it. Mix equal parts 3% hydrogen peroxide (the standard drugstore concentration) and water. Dab it onto the sore with a cotton swab or use it as a brief rinse. Don’t swallow it, and limit use to a few times a day. You may notice some foaming and mild stinging, both of which are normal.
Prescription Treatments for Stubborn Sores
If over-the-counter options aren’t cutting it, a doctor or dentist can prescribe a steroid dental paste. The most common one contains a low-dose corticosteroid that calms the immune response driving the ulcer. You press a small dab, about a quarter inch, directly onto the sore until a thin film develops. Don’t rub it in. The paste works best applied at bedtime so it stays in contact with the sore overnight, and can be used two or three times daily after meals for more severe cases.
Prescription-strength mouth rinses are another option. These may contain a corticosteroid solution or an antimicrobial that reduces secondary infection and inflammation. For people who get frequent, recurring canker sores, a doctor may also investigate underlying causes like celiac disease, inflammatory bowel conditions, or vitamin deficiencies that can be corrected.
What Helps Sores Heal Faster
Treatment helps with pain, but a few habits speed up actual healing. Avoid acidic foods and drinks like citrus, tomatoes, coffee, and carbonated beverages, all of which irritate the exposed tissue and slow recovery. Spicy foods do the same. Switch to a soft-bristled toothbrush temporarily, and use a toothpaste free of sodium lauryl sulfate (SLS), a foaming agent linked to more frequent canker sores in some people.
Eating soft, cool foods like yogurt, smoothies, and mashed potatoes reduces friction against the sore. Drinking through a straw can help liquids bypass it entirely. Ice chips held against the sore provide temporary numbing and reduce inflammation without any products at all.
Keeping your mouth clean matters more than usual while a sore is open. Bacteria colonizing the ulcer can delay healing and increase pain. Gentle brushing and consistent rinsing after meals create an environment where the tissue can repair itself more efficiently.
Preventing the Next One
If you get canker sores regularly, prevention is more effective than treatment. Track your triggers: for many people, a specific food (nuts, chocolate, strawberries, cheese, or anything highly acidic) reliably precedes an outbreak. Stress is another major trigger, and flare-ups often coincide with periods of poor sleep or high anxiety.
Nutritional gaps play a surprisingly large role. Low levels of iron, zinc, folate, and B12 are all associated with recurrent canker sores. A simple blood test can identify deficiencies, and correcting them with diet or supplements often reduces how frequently sores appear. Foods rich in these nutrients include leafy greens, beans, fortified cereals, eggs, and lean meats.
Avoiding mouth injuries helps too. Chew slowly, be cautious with sharp or crunchy foods, and if orthodontic hardware or a rough tooth edge keeps cutting the inside of your mouth, have your dentist smooth or adjust it. That repeated minor trauma is one of the most common and most fixable causes of canker sores.