Most canker sores heal on their own within 10 to 14 days, but the right combination of pain relief, mouth rinses, and trigger avoidance can cut that timeline shorter and keep new sores from forming. Here’s what actually works, from immediate relief to long-term prevention.
What a Normal Healing Timeline Looks Like
Not all canker sores are created equal. Mild ones that pop up a few times a year often resolve in two to three days with minimal pain and no treatment at all. More painful ulcers can last up to 10 days. The standard minor canker sore, the kind most people get on the inside of the cheeks or lips, typically heals within 10 to 14 days without scarring.
Major canker sores, which are larger than a pea (roughly one centimeter across), are a different story. These can take up to six weeks to heal and may leave a scar. If your sore falls into this category or lasts longer than two weeks, that’s worth a call to your doctor or dentist.
Rinses You Can Make Right Now
A simple saltwater or baking soda rinse is one of the fastest ways to reduce pain and create a cleaner environment for healing. Memorial Sloan Kettering Cancer Center recommends mixing 1 teaspoon of salt and 1 teaspoon of baking soda into 1 quart (4 cups) of water. You can also use just salt or just baking soda at the same ratio. Swish gently for 30 seconds and spit. Repeat several times a day, especially after meals.
The salt draws fluid from the inflamed tissue, which helps reduce swelling. The baking soda neutralizes acids in your mouth that irritate the open sore. Neither will sting as badly as you might expect at this dilution, though the first rinse on a fresh ulcer can be uncomfortable for a few seconds.
Over-the-Counter Products That Help
Topical gels and pastes work best when you apply them as soon as you notice the sore forming. Benzocaine, the active ingredient in products like Anbesol and Zilactin-B, numbs the area on contact. It won’t speed healing, but it makes eating and talking far less painful. Hydrogen peroxide rinses like Peroxyl serve as antiseptic washes that keep the sore clean and reduce bacteria around the ulcer.
For something stronger, products containing fluocinonide (a topical steroid found in Lidex and Vanos) reduce inflammation and can shorten healing time. These are available by prescription, so you’d need to ask your doctor or dentist. Applying any topical treatment to a dry sore with a cotton swab, rather than a finger, gives you better coverage and keeps the product in place longer.
Foods That Make Things Worse
Acidic and abrasive foods are the two biggest dietary culprits. Citrus fruits, tomatoes, strawberries, and coffee all contain acids that directly irritate the exposed tissue of a canker sore. Soda is a double hit: high in acid and often loaded with corn syrup, both of which promote inflammation. Even diet soda is just as acidic as regular.
Spicy foods containing hot peppers irritate the soft tissue lining your mouth in a similar way. And sharp, crunchy foods like chips, pretzels, and nuts can physically scrape against the sore or even create new micro-injuries that develop into additional ulcers. While you have an active sore, stick to soft, bland, room-temperature foods. Yogurt, oatmeal, mashed potatoes, and smoothies (skip the citrus) are safe bets.
Switch Your Toothpaste
This is one of the simplest changes with the strongest evidence behind it. Sodium lauryl sulfate (SLS) is a foaming agent in most toothpastes, and it’s a well-documented trigger for canker sores. A meta-analysis found that people who switched to SLS-free toothpaste developed about one fewer ulcer per cycle, and their sores healed roughly two days faster. They also experienced significantly less pain and fewer total episodes.
SLS-free toothpastes are widely available. Brands like Sensodyne, Biotene, and several others skip the ingredient entirely. Check the back label for “sodium lauryl sulfate” in the inactive ingredients list. If you get canker sores more than a couple of times a year, this one swap is worth trying before anything else.
Nutritional Deficiencies to Rule Out
Recurrent canker sores, the kind that keep coming back every few weeks, are sometimes driven by nutritional gaps your body is signaling about. Vitamin B12 deficiency is the most common culprit, since B12 supports tissue repair and red blood cell production. When levels drop, the lining of your mouth heals poorly and becomes more vulnerable to ulceration.
Iron deficiency is another frequent cause. Low iron reduces oxygen delivery to tissues, which slows healing and makes the mouth lining more fragile. Folic acid (vitamin B9) plays a direct role in cell growth and repair, so a shortfall can trigger oral inflammation and cracking. Zinc deficiency delays wound healing and weakens immune function, and low vitamin C impairs collagen formation, which your mouth needs to close wounds.
If your canker sores are frequent and you can’t pin them to an obvious trigger like acidic food or a rough toothbrush, a simple blood test can check these levels. Correcting a deficiency often reduces or eliminates recurrences entirely.
Laser Treatment for Severe Cases
For people who deal with large or frequently recurring canker sores, some dental offices now offer low-level laser treatment. The procedure takes just a few minutes per sore, provides immediate pain relief, and can reduce healing time to about two days. The laser kills bacteria at the sore site and essentially cauterizes the ulcer, which also has the potential to prevent sores from recurring in that same spot.
This isn’t a first-line option for the occasional canker sore, but it’s worth knowing about if you’re dealing with major ulcers that take weeks to heal or sores that keep forming in the same location. Ask your dentist whether they offer diode laser treatment for soft tissue lesions.
Preventing the Next One
Most canker sores are triggered by a combination of minor trauma and an overactive immune response. Your immune system’s inflammatory cells target the damaged mouth lining, which is why a small bite to your cheek can turn into a full ulcer in some people but not others. You can’t change your immune response, but you can reduce the triggers that set it off.
- Use a soft-bristled toothbrush to minimize abrasion to your gums and cheeks
- Switch to SLS-free toothpaste to remove a known chemical irritant
- Limit acidic foods and drinks during periods when you’re prone to outbreaks
- Address nutritional gaps with a balanced diet or targeted supplements if blood work shows a deficiency
- Manage stress, which is a well-recognized trigger for flare-ups in susceptible people
If you’re getting canker sores more than three times a year, they’re larger than a centimeter, or they last beyond two weeks, those are signs that something beyond a simple irritation is going on. A doctor can evaluate whether an underlying condition, medication side effect, or immune issue is contributing.