Most canker sores heal on their own within 10 to 14 days, but you can cut down the pain and speed that timeline with the right combination of home remedies and over-the-counter products. The key is starting treatment early, ideally at the first tingling sensation, and keeping the sore clean while reducing inflammation.
Salt Water and Baking Soda Rinses
The simplest and cheapest option is already in your kitchen. Dissolve one teaspoon of baking soda in half a cup of warm water and swish it around your mouth for 30 to 60 seconds. A basic salt water rinse works too. Both approaches neutralize acids in your mouth that irritate the open sore, and they create an environment that’s less hospitable to bacteria. Do this several times a day, especially after meals when food particles can aggravate the ulcer.
These rinses won’t numb the pain instantly, but they consistently shorten healing time when used regularly. They’re also gentle enough to use alongside any other treatment on this list.
Topical Numbing Gels
Over-the-counter gels containing benzocaine or lidocaine are the fastest way to stop canker sore pain. Products like Orajel and Anbesol use these ingredients at concentrations around 20% to temporarily block nerve signals in the tissue. Apply a small amount directly to the sore with a clean finger or cotton swab. The relief kicks in within a minute or two and typically lasts long enough to eat or drink comfortably.
For a protective barrier that also numbs, look for oral pastes that stick to the sore and shield it from friction. These are especially useful if your canker sore is on your inner cheek or gum line where it rubs against your teeth constantly.
The Alum Powder Method
Alum powder, the same astringent used in pickling, is a lesser-known remedy that many people swear by. Mix a tiny amount of alum powder with a single drop of water to form a thick paste. Dab it directly onto the canker sore and leave it in place for at least one minute, then rinse your mouth thoroughly. The alum works as an astringent, drawing moisture out of the sore tissue and shrinking it. It stings, sometimes intensely, but the pain from the sore itself often decreases significantly afterward. Repeat once daily until the sore is gone.
Switch Your Toothpaste
If you get canker sores repeatedly, your toothpaste may be part of the problem. Many standard toothpastes contain sodium lauryl sulfate (SLS), a foaming agent that strips away the protective mucous lining inside your mouth. In one clinical trial, patients who switched from SLS toothpaste to an SLS-free version went from averaging 14.3 ulcers over three months to just 5.1. That’s a 64% reduction from a single change.
SLS-free toothpastes are widely available. Brands like Sensodyne, Biotene, and Tom’s of Maine (some formulas) skip SLS entirely. If you’re dealing with a current sore, switching now won’t heal it overnight, but it can make a noticeable difference in how often you get the next one.
Prescription Options for Severe Sores
Minor canker sores, the most common type, are small and heal within two weeks. But major canker sores can grow much larger and linger for up to six weeks. If your sores are large, extremely painful, or keep coming back, a prescription steroid rinse can knock down the inflammation far more aggressively than anything over the counter. These rinses are swished around the mouth for about two minutes several times a day and significantly reduce both pain and healing time.
Another clinical option is chemical cauterization, where a dentist or doctor applies a substance like silver nitrate directly to the sore. This destroys the damaged tissue and can provide near-immediate pain relief, though the area still needs a few days to fully heal. It’s worth asking about if you have a sore that’s making it hard to eat or talk.
Nutritional Gaps That Cause Recurrence
Recurring canker sores are frequently linked to nutritional deficiencies, particularly B12, folate, and iron. Your body uses these nutrients to maintain healthy tissue in the mouth lining, and when levels drop low enough, ulcers are one of the first signs. A comprehensive review in Frontiers in Oral Health found that B12 levels below 200 pg/ml and folate levels below 3 ng/ml are diagnostic thresholds associated with recurrent outbreaks.
If you get canker sores more than a few times a year, it’s worth having your levels checked with a simple blood test. Correcting a B12 deficiency, for instance, often involves a daily oral supplement of 1,000 mcg. Folate deficiency responds to 400 to 800 mcg daily. These aren’t overnight fixes for the sore in your mouth right now, but they can dramatically reduce how often you deal with them going forward.
Understanding the Healing Timeline
Not all canker sores follow the same schedule. The mildest form can resolve in as little as two to three days, with pain fading quickly and the tissue closing over. The more common minor ulcers take 10 to 14 days from first appearance to full healing. Major ulcers, which are deeper and larger, can persist for six weeks and sometimes leave scars.
The painful peak usually hits around days three through five. After that, the sore gradually shrinks and the surrounding redness fades. If a canker sore hasn’t shown any improvement after two weeks, or if you develop a fever alongside it, that’s a signal something else may be going on.
Canker Sores vs. Cold Sores
Before treating a mouth sore, make sure you’re dealing with the right one. Canker sores and cold sores look and behave differently, and they require completely different treatments. Canker sores form inside the mouth only, on the inner cheeks, lips, tongue, or gums. They appear as single round white or yellow sores with a red border, and they are not contagious.
Cold sores (fever blisters) show up outside the mouth, typically around the border of the lips. They look like clusters of small fluid-filled blisters rather than a single ulcer, and they’re caused by the herpes simplex virus, making them highly contagious. If your sore is on the outside of your lip and looks blistered, none of the treatments in this article will help. You’ll need an antiviral medication instead.