Most canker sores heal on their own within 10 to 14 days, but the right combination of home care and over-the-counter treatments can cut down pain significantly and help them resolve faster. The key is reducing irritation, keeping the area clean, and protecting the sore while your mouth does the repair work.
What You’re Dealing With
Canker sores are small, painful ulcers that form inside the mouth, typically on the inner cheeks, lips, or tongue. They appear as white or yellow spots with a red border. They’re not cold sores, which show up outside the mouth around the lips and are caused by a virus. Canker sores aren’t contagious and don’t contain fluid-filled blisters.
Minor canker sores, the most common type, are smaller than 5mm across and heal within about two weeks without scarring. Major canker sores exceed 1cm in diameter, can take up to six weeks to heal, and sometimes leave scars. A rarer type, called herpetiform ulcers, starts as dozens of tiny sores that merge into larger, irregularly shaped ulcers.
Home Remedies That Actually Help
A saltwater and baking soda rinse is one of the most effective things you can do at home. St. Jude Children’s Research Hospital recommends this ratio: 1 teaspoon of table salt and 1 teaspoon of baking soda dissolved in 4 cups of warm water. Swish about a tablespoon of the solution in your mouth for 15 to 30 seconds, then spit it out. The baking soda creates a mildly alkaline environment that soothes irritation and helps keep the area clean. You can repeat this several times a day, especially after meals.
Applying a small amount of milk of magnesia directly to the sore with a cotton swab can also coat and protect it. Some people dab honey on the ulcer, which acts as a natural barrier and has mild antibacterial properties. The goal with any topical home remedy is the same: create a protective layer so food and saliva don’t constantly aggravate the raw tissue.
Over-the-Counter Treatments
Numbing gels and ointments containing benzocaine are widely available and provide temporary pain relief. Apply the gel directly to the sore up to four times a day. These products shouldn’t be used for more than two days without checking with a dentist or doctor, as prolonged use can cause its own irritation.
OTC oral adhesive pastes create a protective film over the sore. These work best when you dab a small amount onto the ulcer and let it develop into a smooth coating without rubbing it in. Rubbing causes the paste to crumble and feel gritty instead of forming the protective barrier you want. Press gently, let it set, and it will shield the sore from friction while you eat and talk.
Antiseptic rinses containing hydrogen peroxide (diluted) can help keep the sore clean and prevent a secondary bacterial infection from slowing healing. Look for mouth rinses specifically labeled for canker sores or oral wounds.
What to Eat and Avoid
What you put in your mouth matters as much as what you put on the sore. Acidic foods sting on contact and can delay healing. That includes citrus fruits, tomatoes, berries, pineapple, vinegar, coffee, alcohol, and fruit juice. Even foods you might not think of as acidic, like tomato-based pasta sauce, can set off a wave of pain.
Crunchy or rough-textured foods physically scrape the ulcer and reopen healing tissue. Avoid granola, pretzels, crusty bread, popcorn, potato chips, and crackers until the sore has closed. Stick with soft foods: yogurt, mashed potatoes, scrambled eggs, smoothies, and soups that have cooled to a comfortable temperature. Very hot food and drinks irritate the sore just as much as acidic ones.
Prescription Options for Stubborn Sores
If your canker sore isn’t responding to home care or keeps getting worse, a dentist or doctor can prescribe a steroid dental paste. This is a prescription-strength anti-inflammatory that you press onto the sore in a thin layer (again, without rubbing) to reduce swelling and speed healing. It works by calming the overactive immune response that’s keeping the ulcer inflamed.
For severe or frequently recurring sores, some dental offices offer silver nitrate cauterization. This involves applying a chemical to the surface of the ulcer that essentially seals it. Research has found that silver nitrate provides rapid pain relief, with symptoms resolving in just over one day on average compared to nearly five days with a placebo. The procedure itself causes a brief sting, but the pain drops significantly within hours.
Why You Keep Getting Them
If canker sores are a recurring problem, the cause is worth investigating. One of the most common and overlooked triggers is sodium lauryl sulfate (SLS), the foaming agent in most toothpastes. Dental researchers in the US and Norway have identified SLS as a significant contributor to canker sore formation. Switching to an SLS-free toothpaste is one of the simplest changes you can make, and for many people it dramatically reduces how often sores appear.
Nutritional deficiencies also play a role. Low levels of vitamin B12, folate, and iron (ferritin) are all linked to recurrent canker sores. If you’re getting sores frequently, it’s worth asking your doctor to check these levels with a simple blood test. Correcting a deficiency through diet or supplements can reduce outbreaks substantially.
Other common triggers include stress, hormonal changes, minor mouth injuries (like biting your cheek or irritation from braces), and certain foods that seem to provoke sores in susceptible people. Keeping a simple log of what you ate and what was happening in your life before an outbreak can help you identify your personal triggers over time.
Signs a Canker Sore Needs Professional Attention
Most canker sores are painful but harmless. However, Cleveland Clinic identifies two specific red flags: sores that last longer than two weeks, and sores larger than one centimeter (roughly the size of a pea). Either of these warrants a visit to your dentist or doctor, as persistent or unusually large ulcers occasionally need a biopsy to rule out other conditions. The same applies if you’re running a high fever alongside the sore, if you’re getting sores so frequently that new ones appear before old ones heal, or if the pain is severe enough that you can’t eat or drink adequately.