Most canker sores heal on their own within 10 to 14 days, but you don’t have to wait it out in pain. Several treatments can shrink the sore faster, reduce pain significantly, and help prevent new ones from forming. The right approach depends on how large the sore is and how often you get them.
What You’re Dealing With
Canker sores (aphthous ulcers) are small, shallow wounds inside the mouth, usually on the inner cheeks, lips, tongue, or soft palate. They’re not contagious and they’re not cold sores, which appear on the outside of the mouth and are caused by a virus. Canker sores are an immune response, and their exact trigger varies from person to person.
Most are minor, less than a centimeter across, and resolve within two weeks without scarring. Major canker sores, those larger than a centimeter, can take up to six weeks to heal and sometimes leave a scar. If yours is unusually large or hasn’t improved after two weeks, that’s worth a visit to your dentist or doctor.
Fastest Over-the-Counter Options
The quickest relief comes from topical numbing agents containing benzocaine, available under brand names like Anbesol, Kank-A, and Zilactin-B. These won’t speed healing, but they’ll numb the area within minutes so you can eat and talk without wincing. Apply directly to the sore as needed, especially before meals.
Antiseptic rinses containing hydrogen peroxide (like Orajel Antiseptic Mouth Sore Rinse or Peroxyl) serve a different purpose. They clean the ulcer and reduce bacteria in the area, which can help prevent the sore from getting worse or becoming infected. You can use both approaches together: rinse first, then apply a numbing gel.
Home Remedies That Actually Work
Salt Water Rinse
A salt water rinse is the simplest and cheapest option. Mix one teaspoon of salt into one cup of warm (not hot) water and swish for 30 seconds. It stings initially but helps dry out the sore and keep the area clean. Repeat a few times a day, particularly after eating.
Honey
Honey is more than folk medicine for canker sores. A randomized controlled trial comparing honey to a topical corticosteroid and a protective paste found that honey outperformed both. Patients who applied honey four times a day for five days had significantly faster reduction in ulcer size, fewer days of pain, and less redness around the sore. No side effects were reported. Use raw, unprocessed honey and dab it directly on the sore after meals and before bed. Try not to eat or drink for a few minutes afterward so it stays in contact with the ulcer.
Baking Soda Paste
Mix a small amount of baking soda with a few drops of water to form a paste and apply it directly to the sore. Baking soda neutralizes acids in the mouth that can irritate the ulcer. Like salt water, it will sting briefly.
Prescription Treatments for Stubborn Sores
If over-the-counter options and home remedies aren’t cutting it, or if you get canker sores frequently, a doctor or dentist can prescribe stronger treatments. The most common is a steroid dental paste (triamcinolone acetonide, sold as Kenalog in Orabase). You press a small amount onto the sore with a cotton swab to form a thin protective film. It’s applied after meals and at bedtime. The key is pressing it on gently rather than rubbing, which makes the paste crumble and lose contact with the sore.
For very painful sores, some dentists offer silver nitrate cauterization, a quick in-office procedure where a chemical is applied directly to the ulcer. It sounds aggressive, but research shows it resolves symptoms in roughly one day on average, with significant pain reduction compared to untreated sores. No adverse effects were reported in clinical studies. The tradeoff is a brief, intense sting during application.
Dental laser treatment is another in-office option that reduces inflammation and speeds healing. Not every dental office offers it, but it’s becoming more widely available.
Preventing New Canker Sores
Check for Nutritional Deficiencies
If you get canker sores repeatedly, a vitamin deficiency may be the underlying cause. One study found that over 50% of people with recurrent canker sores were deficient in vitamin B12, compared to none in the control group. Folate levels were also significantly lower in people who got frequent sores. Iron deficiency (low ferritin) played a smaller role. If your sores keep coming back, ask your doctor to check your B12, folate, and iron levels with a simple blood test. Correcting a deficiency can dramatically reduce how often sores appear.
Watch Your Triggers
Common triggers include acidic foods (citrus, tomatoes, pineapple), spicy foods, physical trauma from braces or biting your cheek, and emotional stress. Keeping a simple log of what you ate or what was happening in the day or two before a sore appeared can help you identify your personal triggers over time.
The SLS-Free Toothpaste Question
You’ll see frequent advice to switch to a toothpaste without sodium lauryl sulfate (SLS), the foaming agent in most toothpastes. The theory is that SLS irritates the lining of the mouth and makes sores more likely. The actual evidence is mixed. A 2019 review found there wasn’t enough data to confirm that SLS-free toothpastes reduce ulcer frequency, duration, or pain, and at least one well-designed study found no significant difference. That said, some people do report fewer sores after switching, and SLS-free toothpastes are easy to find and inexpensive, so it’s a low-risk experiment worth trying if you get sores often.
When a Sore Needs Medical Attention
A canker sore that hasn’t healed after two to three weeks, keeps growing, or comes with a fever deserves a professional look. Oral cancers can sometimes mimic a canker sore in appearance, but the key differences are that cancerous lesions don’t heal on a normal timeline and tend to feel firm rather than soft. Your doctor or dentist will do a visual exam and feel the area. If anything looks suspicious, they may recommend a biopsy. This is uncommon, but the distinction matters enough that a sore lasting well beyond two weeks shouldn’t be ignored.