Most canker sores heal on their own within one to two weeks, but the right combination of topical treatments and habit changes can cut pain dramatically and speed that timeline. The single most effective thing you can do is apply a numbing or protective gel the moment you notice the sore forming, before it fully develops.
Why Canker Sores Form
Canker sores are not infections. They’re the result of your own immune system attacking the thin tissue lining your mouth. Certain T cells destroy patches of oral tissue, and the process is fueled by a cascade of inflammatory signaling molecules that keep the area inflamed and painful. People who get canker sores frequently show higher levels of these inflammatory markers in their blood even between outbreaks, which helps explain why some people are prone to them and others never get one.
Common triggers include biting the inside of your cheek, irritation from braces or dental work, stress, hormonal shifts, and certain foods. Nutritional deficiencies in iron, zinc, B12, or folate also increase susceptibility. None of these “cause” canker sores in the way a virus causes a cold sore. They tip the balance in someone whose immune system is already primed to overreact.
Over-the-Counter Treatments That Work
Topical numbing gels containing benzocaine are the fastest way to get pain relief. Products like Anbesol, Orabase, and Zilactin-B coat the sore and block nerve signals in the area within minutes. Apply them directly to the ulcer with a clean finger or cotton swab, ideally before meals so you can eat without wincing. Reapply as needed throughout the day.
Hydrogen peroxide rinses (like Orajel Antiseptic Mouth Sore Rinse) serve a different purpose. They clean the ulcer and reduce the bacterial load around it, which can help prevent secondary infection and support faster tissue repair. You can also make a simple rinse at home by mixing one part 3% hydrogen peroxide with one part water, swishing gently, and spitting.
Protective pastes that form a barrier over the sore are especially useful if the ulcer is in a spot that constantly rubs against your teeth or cheek. These work less by treating the sore and more by shielding it from further irritation, which is often what makes the difference between a sore that lingers and one that resolves quickly.
Home Remedies Worth Trying
A saltwater rinse is the simplest and most reliable home option. Dissolve about half a teaspoon of salt in a cup of warm water, swish for 30 seconds, and spit. It stings briefly but helps draw fluid from the swollen tissue and creates an environment that’s less hospitable to bacteria. Repeat three or four times a day.
Baking soda rinses work similarly. Mix one teaspoon of baking soda in half a cup of water and swish. Baking soda neutralizes acids in the mouth that can irritate the open sore. You can also make a paste with a small amount of water and dab it directly on the ulcer, though this can be uncomfortable for the first few seconds.
Placing a small amount of honey directly on the sore several times a day has shown some benefit in small studies. Honey has natural anti-inflammatory and antimicrobial properties, and it adheres to wet tissue reasonably well. It won’t numb the area, but it may help the tissue heal a day or two faster.
When to Ask About Prescription Options
If over-the-counter products aren’t providing enough relief, or if you get canker sores frequently, prescription options can make a significant difference. Steroid-based topical gels like fluocinonide suppress the immune overreaction at the site, reducing inflammation and pain more aggressively than numbing agents alone. These are applied directly to the sore, typically several times a day.
For larger or more numerous sores, a prescription steroid mouth rinse lets you treat the entire mouth at once using a swish-and-spit technique. This is particularly useful when sores appear in hard-to-reach spots like the back of the throat or soft palate.
Chemical cauterization is another option your dentist or doctor can perform in the office. A single application of silver nitrate to the ulcer reduced pain severity within one day for 70% of patients in a controlled trial, compared to just 11% with a placebo treatment. The tradeoff: it doesn’t actually speed healing. The sores still took about five and a half days to close in both groups. So cauterization is best understood as a pain management tool, not a cure.
Foods to Avoid While You Have One
Acidic foods like citrus fruits, tomatoes, and vinegar-based dressings directly irritate the exposed tissue of a canker sore. So do spicy foods, salty chips, and crunchy items with sharp edges (think tortilla chips and crusty bread). These foods don’t cause canker sores, but they can make an existing one significantly more painful and may slow healing by repeatedly aggravating the wound.
Stick to softer, milder foods while the sore is active. Yogurt, bananas, scrambled eggs, oatmeal, and smoothies are easier on your mouth. Drinking through a straw can help keep acidic or carbonated beverages away from the sore.
Preventing the Next One
If you get canker sores repeatedly, switching your toothpaste may be the single highest-impact change you can make. Most mainstream toothpastes contain sodium lauryl sulfate (SLS), a foaming agent that strips the protective mucus layer from your mouth’s lining. In one study, people who switched from an SLS-containing toothpaste to an SLS-free version saw a 64% reduction in canker sore frequency, dropping from an average of 14.3 ulcers over three months to just 5.1. Several SLS-free options are now widely available, including Sensodyne, Biotene, and Verve.
Beyond toothpaste, pay attention to patterns. If your sores consistently follow periods of poor sleep or high stress, that’s your immune system signaling that it’s being pushed. If they appear after eating certain foods, like walnuts, chocolate, strawberries, or cheese, those may be individual triggers worth avoiding. And if you have braces or a rough dental appliance, orthodontic wax over the irritating edge can prevent the mechanical trauma that sets off the whole cycle.
Sores That Need a Closer Look
A typical canker sore is small (under a centimeter), round or oval, and heals within two weeks without scarring. If a sore persists beyond two weeks, grows unusually large, keeps coming back in the same spot, or is accompanied by fever and significant swelling, it warrants a professional evaluation. Oral lesions that last longer than two weeks after any obvious irritant is removed are generally recommended for biopsy to rule out other conditions. This isn’t common with ordinary canker sores, but it’s worth knowing the threshold.