Most canker sores heal on their own within one to two weeks, but the right treatment can cut pain significantly and speed up that timeline. The approach depends on severity: mild sores respond well to over-the-counter products and home remedies, while larger or frequently recurring ulcers may need prescription treatment or an in-office procedure.
What’s Actually Happening Inside a Canker Sore
Canker sores aren’t infections. They’re the result of your own immune system attacking the lining of your mouth. In people who are prone to them, an inflammatory signaling molecule called TNF-alpha triggers a chain reaction that ends with immune cells (specifically a type of white blood cell called CD8+ T-cells) destroying the surface tissue of your cheeks, gums, or tongue. That’s why the sore looks like a shallow crater with a white or yellowish center surrounded by a red border.
Because the underlying mechanism is immune-driven, treatments that calm inflammation tend to work better than antiseptics alone. It also explains why canker sores often flare during periods of stress, poor sleep, or nutritional deficiency, all of which affect immune regulation.
Over-the-Counter Pain Relief
The fastest way to get temporary relief is a topical numbing gel containing benzocaine, typically sold in a 20% concentration for oral use. It kicks in within a minute of application, but the numbness only lasts about 10 minutes. That short window makes it most useful right before eating or drinking, when the sore is most likely to hurt. You can reapply several times a day.
Protective oral pastes work differently. Instead of numbing the sore, they form a barrier film over it, shielding the raw tissue from food, drinks, and your teeth. These tend to provide longer-lasting comfort than numbing gels, though they won’t speed healing on their own. Look for products marketed as oral wound rinses or protective pastes in the dental care aisle.
Antiseptic mouth rinses containing hydrogen peroxide (diluted) or chlorhexidine can help keep the ulcer clean and reduce the chance of secondary bacterial irritation. A simple DIY alternative is a warm saltwater rinse: half a teaspoon of salt dissolved in eight ounces of water, swished gently for 30 seconds a few times a day.
Prescription Options for Severe or Recurring Sores
If your canker sores are large (bigger than a centimeter), last longer than two weeks, or come back frequently, over-the-counter products probably aren’t enough. Prescription topical corticosteroids are the standard next step. These work by directly suppressing the inflammatory immune response that created the ulcer in the first place, reducing both pain and healing time. Your doctor or dentist may prescribe a steroid paste or a steroid mouth rinse depending on where the sore is and how many you have at once.
For people who get frequent outbreaks (sometimes called recurrent aphthous stomatitis), systemic medications that broadly modulate the immune response are sometimes considered, though these carry more side effects and are reserved for truly disabling cases.
In-Office Cauterization
Chemical cauterization is a quick procedure where a dentist or doctor applies a substance directly to the sore to destroy the damaged surface tissue, essentially resetting the healing process. Two options are commonly used, and they aren’t equally effective.
Debacterol, a topical solution of sulfuric acid and sulfonated phenolics, chemically cauterizes the sore and has been shown to reduce healing time to about a week. Silver nitrate is another cauterizing option, but it hasn’t been shown to speed healing. It can, however, provide noticeable pain relief. Both are applied in a single brief visit.
Dental laser treatment is a newer alternative. The laser removes surface irritation, reduces inflammation, and stimulates healing. Many patients report immediate pain relief after treatment. Laser therapy is particularly worth considering if your ulcers are especially painful, slow to heal, or keep coming back in the same spot.
Home Remedies That Have Some Evidence
Honey applied directly to a mouth ulcer has real anti-inflammatory and wound-healing properties. While most controlled trials have focused on cold sores rather than canker sores specifically, honey has consistently shown healing timelines comparable to pharmaceutical treatments in oral lesion research. If you try this, use raw or medical-grade honey, apply it directly to the sore several times a day, and avoid eating or drinking for 15 minutes afterward.
Chamomile tea bags (cooled and held against the sore), aloe vera gel, and milk of magnesia dabbed onto the ulcer are other common home remedies. The evidence behind these is mostly anecdotal, but they’re low-risk and some people find them soothing.
Nutritional Deficiencies and Prevention
Recurring canker sores are linked to low levels of iron, folate, zinc, and vitamin B12. A clinical trial tested daily sublingual vitamin B12 tablets (1,000 micrograms taken before bed) over six months in people with recurrent aphthous ulcers. The study found benefits regardless of whether participants had low B12 levels at the start, suggesting the vitamin may play a role in immune regulation beyond simply correcting a deficiency.
If you get canker sores more than a few times a year, it’s worth asking your doctor to check your levels of these nutrients with a simple blood test. Correcting a deficiency can dramatically reduce how often sores appear.
Beyond nutrition, common triggers include acidic or spicy foods (citrus, tomatoes, hot peppers), toothpaste containing sodium lauryl sulfate (SLS), mouth injuries from braces or accidental biting, and hormonal changes. Switching to an SLS-free toothpaste is one of the easiest changes you can make, and many people notice fewer outbreaks within a month or two.
When a Canker Sore Needs Medical Attention
A typical canker sore is small, shallow, and gone within two weeks. You should get it looked at if the sore is unusually large (a centimeter or more across), lasts longer than three weeks, spreads or multiplies rapidly, comes with fever, or makes it genuinely difficult to eat or drink enough to stay hydrated. Persistent ulcers that don’t follow the normal healing pattern sometimes need a biopsy to rule out other conditions, including oral lichen planus or, rarely, oral cancer.