Most canker sores heal on their own within 4 to 14 days, but you can speed that up and reduce pain significantly with the right approach. These small, shallow ulcers appear inside the mouth on soft tissue like the inner cheeks, gums, tongue, or soft palate. They’re not contagious and not caused by a virus, which makes them different from cold sores that show up on the outside of the lips.
Start Treatment Early for Faster Healing
The single most important thing you can do is treat the sore as soon as you notice it. Over-the-counter products come as pastes, creams, gels, or liquids, and they work best when applied to the sore right when it appears. The most common active ingredient is benzocaine, a topical numbing agent found in products like Anbesol and Zilactin-B. It won’t cure the sore, but it blocks pain on contact so you can eat and talk more comfortably.
Antiseptic mouth rinses containing hydrogen peroxide (like Peroxyl) help keep the area clean and may reduce healing time. You can also make a simple rinse at home: dissolve half a teaspoon of salt in a cup of warm water and swish it around the sore for 30 seconds, then spit. Repeat a few times a day. A baking soda rinse works similarly. These won’t sting as badly as you’d expect, and they help reduce bacteria around the ulcer.
Honey applied directly to the sore is another option with genuine evidence behind it. Research published in the Journal of Food Science and Technology found that honey preparations applied to oral ulcers twice daily reduced ulcer size and supported faster healing. You can dab a small amount of raw honey onto the sore with a clean finger after meals and before bed. It will wash away with saliva, so reapplication matters.
What to Avoid While You Heal
Acidic and spicy foods are the biggest offenders. Citrus fruits, tomatoes, vinegar-based dressings, hot peppers, and chips with sharp edges all irritate the ulcer and slow healing. Stick to soft, bland foods while the sore is at its worst. Yogurt, mashed potatoes, oatmeal, and smoothies are good choices.
Your toothpaste may also be making things worse. Sodium lauryl sulfate (SLS), the foaming agent in most toothpastes, has been linked to longer-lasting canker sores and more pain. A meta-analysis of four randomized controlled trials found that people who switched to SLS-free toothpaste experienced shorter ulcer duration and lower pain scores. If you get canker sores regularly, switching toothpaste is one of the simplest changes you can make. Brands like Sensodyne and some versions of Tom’s of Maine are SLS-free.
When a Canker Sore Needs More Than Home Care
The typical canker sore is under 1 cm across, usually 2 to 5 mm, and clears up within two weeks without any treatment. But major canker sores, the less common type, can be 1 to 3 cm in diameter and last anywhere from 10 days to 6 weeks. These larger sores often sit deeper in the tissue and can be genuinely debilitating.
For severe or stubborn sores, a doctor or dentist can prescribe a corticosteroid mouth rinse. Dexamethasone, one of the most commonly prescribed options, works by reducing inflammation and has been shown in randomized trials to significantly shrink ulcer size and lower pain levels. Prescription-strength topical steroids like fluocinonide are also available as gels or pastes applied directly to the sore. These treatments make the biggest difference for people who get large or frequently recurring ulcers.
Why You Keep Getting Canker Sores
If canker sores keep coming back, the cause is often something you can identify and address. The most common triggers fall into a few categories.
Nutritional deficiencies are a well-documented factor. Research has found that people with recurrent canker sores consume significantly less vitamin B12 and folate than the general population. Low iron levels are also common. Studies going back decades have shown that correcting these deficiencies with supplements leads to improvement in symptoms. If you get canker sores more than a few times a year, it’s worth having your B12, folate, and iron levels checked through a simple blood test.
Mechanical injuries are another frequent trigger. Biting the inside of your cheek, brushing too aggressively, or having a rough edge on a dental appliance can all create the initial wound that develops into a canker sore. Stress is consistently linked to outbreaks as well, though the exact mechanism isn’t fully understood.
Canker Sores vs. Cold Sores
These two get confused constantly, but they’re completely different. Canker sores appear inside the mouth and have no known viral cause. Cold sores (fever blisters) appear on the outside of the mouth around the lips and are caused by herpes simplex virus type 1. Cold sores are contagious; canker sores are not. If your sore is on the outer lip or the skin around your mouth, it’s likely a cold sore and requires antiviral treatment rather than the approaches described here.
Red Flags Worth Watching For
Most canker sores are painful but harmless. However, certain patterns warrant a visit to your doctor or dentist: sores lasting longer than two weeks, unusually large sores, new sores appearing before old ones finish healing, sores that extend onto the outer lip border, pain that doesn’t respond to any home treatment, difficulty eating or drinking, or a high fever accompanying the sores. Persistent or unusually frequent canker sores can occasionally signal an underlying condition like celiac disease or an immune disorder that’s worth investigating.