Most canker sores heal on their own within 4 to 14 days, but you can cut down pain and speed up that timeline with the right combination of topical treatments and mouth rinses. The key is starting early: the sooner you treat a canker sore after it appears, the less severe it becomes and the faster it resolves.
Numb the Pain Right Away
The fastest way to get relief is a topical numbing gel containing benzocaine, available over the counter in 10% (regular strength) and 20% (maximum strength) formulations. Brands like Orajel and Anbesol sell both concentrations. Apply the gel directly to the sore up to four times per day, which is the maximum labeled dose. The numbing effect kicks in within minutes and lasts long enough to eat or drink comfortably.
If benzocaine gels aren’t available, try dabbing a small amount of milk of magnesia directly onto the sore with a cotton swab. It coats the ulcer and creates a protective barrier that reduces irritation from food and saliva. You can repeat this three to four times a day.
Rinse With Salt and Baking Soda
A simple alkaline rinse helps keep the sore clean and creates an environment that supports healing. Mix 1 teaspoon of table salt and 1 teaspoon of baking soda into 4 cups of warm water. Swish gently for 30 seconds to a minute, then spit. You can use this rinse several times a day, especially after meals when food debris is most likely to irritate the ulcer.
Salt water alone works too, but adding baking soda neutralizes acids in the mouth that can slow healing and increase pain. Keep a batch in a sealed container on your counter so it’s easy to rinse consistently.
Try Honey as a Topical Treatment
Honey is more than a folk remedy for canker sores. In a clinical trial comparing honey to a prescription steroid paste, honey applied four times a day for five days produced a statistically significant reduction in ulcer size, pain, and redness compared to both the steroid and a plain oral adhesive. The likely reason: honey has natural anti-inflammatory and antimicrobial properties, and its thick consistency keeps it in contact with the sore.
Use plain, unprocessed honey. Dab a small amount directly on the ulcer after meals and before bed. It will sting briefly on contact, but the discomfort fades quickly.
When to Use a Steroid Paste
If your canker sore is large or especially painful, a prescription corticosteroid dental paste can reduce inflammation and accelerate healing. The paste is applied by pressing a small dab (about a quarter inch) onto the sore until a thin film develops. Don’t rub it in. The film adheres to the moist tissue and delivers the anti-inflammatory medication directly to the ulcer.
Apply it at bedtime so the paste stays in contact with the sore overnight. For more severe ulcers, you can apply it two or three times daily, ideally after meals. This treatment works best when started at the earliest sign of a canker sore. It won’t help if the sore is caused by an active infection, so if you suspect something other than a standard canker sore, get it checked first.
Silver Nitrate for Immediate Pain Relief
Silver nitrate sticks, sometimes called caustic pencils, offer a different approach: chemical cauterization. A single application chemically seals the nerve endings on the sore’s surface. In a randomized controlled trial, 70% of patients treated with silver nitrate had significant pain reduction within one day, compared to just 11% in the placebo group. The pain relief lasted for the duration of the sore, with no reported side effects.
The trade-off is that silver nitrate doesn’t actually speed up healing. Both groups in the trial had similar healing rates by day seven. What it does is make the sore dramatically less painful while your body heals it naturally. Silver nitrate sticks are available at some pharmacies, and dentists can also perform the application in-office.
Protect the Sore From Irritation
Healing slows down every time the ulcer gets re-irritated. A few practical steps make a real difference:
- Avoid acidic foods like citrus, tomatoes, and vinegar-based dressings. These sting on contact and can inflame the tissue around the sore.
- Skip spicy and crunchy foods until the sore closes. Chips, crackers, and toast are common culprits for mechanical irritation.
- Switch to a soft-bristled toothbrush and use a toothpaste without sodium lauryl sulfate (SLS), a foaming agent linked to increased canker sore frequency in some people.
- Avoid alcohol-based mouthwashes, which dry out and irritate the tissue. Stick with your salt and baking soda rinse instead.
Reduce Future Outbreaks
If you get canker sores frequently, the issue may partly be nutritional. A review of clinical studies found that taking 1,000 micrograms of sublingual vitamin B12 daily for six months significantly reduced the number, duration, and frequency of outbreaks. The effect was most pronounced after the six-month mark, suggesting it takes time to correct an underlying deficiency. B12 supplements at this dose are inexpensive and widely available.
Iron, zinc, and folate deficiencies are also associated with recurrent canker sores. If you get them more than a few times a year, it’s worth checking your levels with a simple blood test.
What Counts as a Concerning Canker Sore
Standard canker sores (the minor type) are under 1 centimeter across and resolve within two weeks. Major canker sores can reach 1 to 3 centimeters, penetrate deeper into tissue, and take anywhere from 10 days to 6 weeks to heal. If your sore is larger than a pea, lasts longer than two weeks, or comes with fever or difficulty swallowing, it’s time for a professional evaluation. Persistent mouth ulcers can occasionally signal other conditions that need different treatment.