Most canker sores heal on their own within one to two weeks, but the right combination of treatments can cut that timeline roughly in half and dramatically reduce pain in the meantime. The fastest single intervention is chemical cauterization, which can resolve a canker sore in three to five days. If you’re managing things at home, layering pain relief with anti-inflammatory rinses gives you the best shot at speeding recovery.
The Fastest Option: Chemical Cauterization
If you want the closest thing to an instant fix, a prescription product called Debacterol cauterizes the ulcer in a single application. It chemically seals the sore, destroys exposed nerve endings, and provides immediate, lasting pain relief. Most people who use it report full healing within three to five days, compared to the seven to fourteen days an untreated sore typically takes. You’ll need to ask your dentist or doctor for it, so this isn’t something you can grab off the shelf tonight, but it’s worth knowing about if you get canker sores frequently.
Silver nitrate is another cauterization option sometimes used in dental offices. It works similarly by sealing the wound, though it tends to be less comfortable during application. Both options are a single visit, and the pain relief starts immediately.
What You Can Do Right Now at Home
The most effective home approach combines a topical numbing agent for pain with a rinse that keeps the area clean and reduces inflammation. Here’s a practical routine you can start today:
Hydrogen peroxide and Milk of Magnesia: Mix equal parts hydrogen peroxide and water, then dab the mixture directly onto the sore with a cotton swab. Follow immediately by dabbing a small amount of Milk of Magnesia on top. Repeat three to four times a day. The peroxide cleans the wound, while the Milk of Magnesia coats it and neutralizes acid.
Salt water rinse: Dissolve about half a teaspoon of salt in a cup of warm water and swish for 30 seconds. This draws fluid out of the inflamed tissue and helps the sore dry out faster. It stings for a moment, but most people feel better afterward. You can alternate this with a baking soda rinse (one teaspoon of baking soda in half a cup of water), which neutralizes mouth acids that irritate the ulcer.
Numbing gels: Over-the-counter products containing benzocaine (sold as Anbesol, Orabase, and Zilactin-B) numb the sore on contact. Apply them before meals so you can eat without pain. The relief typically lasts about an hour. These gels don’t speed healing, but they make the waiting period far more bearable.
One additional option: rinse with a mixture of half Milk of Magnesia and half liquid Benadryl (diphenhydramine). Swish it around your mouth for about a minute and spit it out. The combination coats the sore, reduces inflammation, and provides mild numbing.
What to Avoid While You’re Healing
Nothing slows canker sore recovery like repeatedly irritating the wound. Acidic foods like tomatoes, citrus fruits, and vinegar-based dressings are the biggest offenders. Spicy food, crunchy chips, and very hot drinks also aggravate the tissue. Stick to softer, blander foods until the sore starts closing up.
Skip any mouthwash that contains alcohol. Alcohol-based rinses burn on contact and dry out the tissue surrounding the sore, which can slow healing and increase pain. Look for alcohol-free alternatives, or stick with the salt water and baking soda rinses described above.
Prescription Options That Speed Healing
If your canker sore is large, unusually painful, or slow to heal, your doctor or dentist can prescribe a corticosteroid paste (like fluocinonide). These work by reducing the inflammation driving the pain and swelling. Unlike numbing gels, steroid pastes actually help the sore heal faster, though they work gradually over several days rather than providing instant relief. You apply them directly to the sore, and they’re most effective when started early.
Adhesive patches and dissolving discs are another option. They create a physical barrier over the sore that protects it from food, your teeth, and your tongue. The protection is moderate, and they don’t actively treat the ulcer, but they can make a big difference if the sore is in a spot that keeps getting bumped.
How Long Each Type Takes to Heal
Not all canker sores are the same, and knowing which type you’re dealing with helps set realistic expectations. Minor canker sores, the most common kind, are smaller than a pea and typically heal within one to two weeks without scarring. These are the ones most responsive to home treatment.
Major canker sores are larger than one centimeter, extremely painful, and can take weeks or even months to fully heal. They often leave scars. If you have a sore this size, professional treatment is worth pursuing early rather than waiting it out. Herpetiform canker sores are rare and look different: instead of a single ulcer, you’ll see clusters of tiny pinpoint sores. Despite looking alarming, they usually heal within about two weeks.
Preventing the Next One
If you get canker sores regularly, your toothpaste might be part of the problem. Sodium lauryl sulfate (SLS), the foaming agent in most major toothpaste brands, is a known soft tissue irritant. It’s the same chemical used in shampoos and household cleaners. Switching to an SLS-free toothpaste is one of the simplest changes you can make. Options include Sensodyne ProNamel, Tom’s of Maine, Hello, Arm & Hammer, and Burt’s Bees Natural Toothpaste.
Nutritional deficiencies also play a role. Low levels of B12, iron, and folate are all linked to recurring canker sores. A clinical trial tested 1,000 micrograms of sublingual vitamin B12 taken daily at bedtime over six months and found it reduced ulcer frequency and pain. If your sores keep coming back, a blood test to check these levels is a practical next step.
Common triggers worth tracking include stress, hormonal changes, food sensitivities (especially to nuts, chocolate, and acidic fruits), and physical trauma from braces, dental work, or accidentally biting your cheek. Keeping a simple log of when sores appear can help you identify your personal pattern.
Signs a Sore Needs Professional Attention
A canker sore that hasn’t healed within a few weeks deserves a closer look. The same goes for sores that are unusually large, more frequent than normal, or accompanied by red, white, or mottled patches in your mouth. A bump under the skin beneath the ulcer is another reason to get it examined. These can all be benign, but persistent mouth sores that don’t follow the normal healing pattern should be evaluated to rule out other conditions, including oral cancer. Your primary care provider can assess it and refer you to a specialist if needed.