Most canker sores heal on their own within one to two weeks, but several home remedies and treatments can reduce pain and speed that timeline. The key is lowering acid levels in your mouth, protecting the sore from further irritation, and avoiding foods that make things worse.
Salt Water and Baking Soda Rinses
The simplest and most effective home treatment is a warm salt water rinse. Salt and baking soda both reduce acid levels in the mouth and decrease inflammation around the ulcer. Less acid means less pain on contact and a better environment for the tissue to repair itself. Dissolve about half a teaspoon of salt (or baking soda) in a cup of warm water and swish gently for 30 seconds, then spit. Doing this a few times a day, especially after meals, keeps the area cleaner and calmer.
Milk of Magnesia as a Coating Agent
Dabbing a small amount of milk of magnesia directly onto the sore creates a protective coating over the raw tissue. It works by neutralizing acid on the ulcer’s surface, which provides fairly quick pain relief. You can apply it with a cotton swab three to four times a day. Some people alternate between a salt water rinse and a milk of magnesia application to get both the cleansing and coating benefits.
Foods That Slow Healing
What you eat while you have a canker sore matters more than most people realize. Acidic foods are the biggest offenders: citrus fruits and juices (oranges, grapefruits, lemons, limes, pineapple), tomatoes and tomato sauce, strawberries, coffee, and soda. All of these bathe the open sore in acid and can intensify pain while delaying recovery. Diet sodas are just as acidic as regular versions.
Spicy foods containing hot peppers irritate exposed tissue in the same way. Physically rough foods like chips, pretzels, and nuts can scrape against the ulcer and reinjure it. While you’re healing, stick to soft, bland, room-temperature foods. Think yogurt, oatmeal, scrambled eggs, mashed potatoes, and smoothies (without citrus).
For some people, chocolate and gluten-containing foods are personal triggers, especially if there’s an underlying sensitivity or allergy. If you notice canker sores tend to follow certain meals, that pattern is worth paying attention to.
Over-the-Counter Options
Topical gels and pastes containing a numbing agent can temporarily block pain at the sore. These are applied directly to the ulcer and form a protective barrier. Look for products specifically labeled for mouth sores at any pharmacy. Apply them after eating and before bed for the most comfortable results, since the medication works on contact and stays effective longer when you’re not eating or drinking.
Antiseptic mouth rinses designed for oral sores can also help keep the area clean and reduce bacteria that might slow healing.
Prescription Treatments for Severe Sores
When canker sores are large, extremely painful, or keep coming back, a doctor or dentist can prescribe a steroid mouth rinse. These prescription rinses reduce inflammation more aggressively than anything available over the counter. The typical routine involves swishing the solution for about a minute after meals and before bed, then spitting it out. To get the most benefit, you should avoid eating or drinking for at least 30 minutes afterward so the medication stays in contact with the tissue.
Major canker sores, the larger and deeper variety, can take six weeks or longer to heal and sometimes leave scars. Prescription treatment is more important for these.
Some dental offices now offer soft-tissue laser treatment for canker sores. The procedure takes about 15 minutes, can provide near-immediate pain relief, and shortens the overall healing time. It’s worth asking about if you get sores frequently.
Preventing Future Sores
One of the most evidence-backed prevention strategies is switching to a toothpaste that doesn’t contain sodium lauryl sulfate (SLS), the foaming agent found in most standard toothpastes. In a preliminary study published in Acta Odontologica Scandinavica, all 10 participants who switched to an SLS-free toothpaste saw improvement, with an average 70% reduction in canker sore frequency compared to their regular toothpaste. SLS-free options are widely available at drugstores and online.
Nutritional deficiencies can also play a role. Low levels of vitamin B12, folate, and iron are all linked to recurrent mouth ulcers. If you get canker sores frequently, it’s reasonable to evaluate whether your diet provides enough of these nutrients. Leafy greens, beans, eggs, meat, and fortified cereals are good sources. A blood test can confirm whether a deficiency is contributing.
Physical trauma is another common trigger. Biting your cheek, brushing too aggressively, or getting poked by braces or a rough tooth edge can all kick off a sore. A soft-bristled toothbrush and a gentler brushing technique help.
When a Sore Isn’t Just a Canker Sore
A standard canker sore hurts from the moment it appears, peaks in pain for a few days, then gradually fades. If a mouth sore lasts longer than two weeks without healing, that’s the clearest signal to get it examined by a doctor or dentist.
Other signs that something different is going on include: a bump or thickening under the sore, red, white, or mottled patches in your mouth, texture changes like rough or crusty areas, numbness in your tongue or mouth, difficulty chewing or moving your jaw, or a sore that keeps changing shape but never actually heals. Oral cancers typically don’t hurt much at first, which is the opposite of canker sores. The pain from cancer builds over time and doesn’t resolve. Unexplained weight loss, persistent bad breath despite good hygiene, or swelling in your neck lasting more than two weeks are also reasons to get checked.
People with weakened immune systems, including those with HIV, can experience canker sores that take months to heal and may need more aggressive treatment.