The fastest relief for a canker sore comes from coating it with something that either numbs the nerve endings or creates a physical barrier between the ulcer and everything in your mouth. Over-the-counter numbing gels containing benzocaine are the most widely used option, but salt water rinses, milk of magnesia, and even honey can all help reduce pain and support healing. Most canker sores resolve on their own within one to two weeks, but what you put on them during that time makes a real difference in how much they hurt.
Numbing Gels and Pastes
Benzocaine gels are the go-to for immediate pain relief. They’re available without a prescription in gel, paste, ointment, spray, and liquid form. You apply a small amount directly to the sore up to four times a day. The numbing effect kicks in within a minute or two and typically lasts long enough to eat or drink comfortably. Children under two should not use benzocaine products.
These gels work best when you dry the sore gently with a tissue before applying. A dry surface helps the product stick rather than slide off immediately. Some formulas combine a numbing agent with a protective coating that stays on longer, which is worth looking for if your sore is in a spot that rubs against your teeth or cheeks.
Salt Water and Baking Soda Rinses
A simple rinse is one of the most effective things you can do, and you probably already have the ingredients. Memorial Sloan Kettering Cancer Center recommends mixing 1 teaspoon of salt and 1 teaspoon of baking soda into 1 quart (4 cups) of water. You can also use just salt or just baking soda at the same ratio. Swish the rinse around your mouth for 30 seconds, then spit. Repeat every four to six hours.
Salt water draws fluid out of the inflamed tissue, which reduces swelling. Baking soda neutralizes acids in the mouth that irritate the open ulcer. The combination won’t numb the sore, and it will sting for a few seconds, but it creates a cleaner healing environment and can shorten recovery time.
Milk of Magnesia
Dabbing a small amount of milk of magnesia directly on the canker sore a few times a day serves two purposes. It coats the ulcer with a protective layer, and it neutralizes the acid around it. You can apply it with a cotton swab after meals or whenever the sore feels especially irritated. Some people alternate between milk of magnesia and a numbing gel, using one for pain and the other for protection.
Alum Powder
Alum powder, the astringent spice found in the spice aisle, is a popular home remedy that draws moisture out of the sore and helps it shrink. Mix a tiny pinch of alum powder with a single drop of water to form a paste, then dab it onto the canker sore. Leave it on for at least one minute before rinsing your mouth thoroughly. You can repeat this once daily until the sore heals. It stings significantly on contact, but many people find the sore feels noticeably better within a day or two.
Honey
Applying raw honey to a canker sore three times a day is a gentler option. A systematic review of clinical studies found that honey performed comparably to standard prescribed treatments for ulcer size and pain, with no adverse effects reported. The results weren’t dramatically better than conventional treatment, but honey has natural anti-inflammatory properties and tastes far better than most of the alternatives. Dab a small amount on the sore after meals and before bed, and try not to eat or drink for a few minutes after applying.
Adhesive Patches and Oral Bandages
Canker sore patches stick directly over the ulcer and form a physical barrier that shields it from food, drinks, and the constant friction of your tongue and cheeks. They’re available at most pharmacies and typically dissolve on their own over several hours. Some contain medication, while others simply protect.
These patches work better than gels for sores in high-friction areas, like the inside of the lip or along the gum line, because standard gels are susceptible to being washed away by saliva and rubbed off by the tongue. The trade-off is that patches can feel bulky, and they don’t adhere well to wet surfaces, so you’ll want to dry the area before applying.
Preventing the Next One
If you get canker sores regularly, your toothpaste may be part of the problem. A foaming agent called sodium lauryl sulfate (SLS), found in most commercial toothpastes, irritates the lining of the mouth and can trigger recurrent sores. A meta-analysis found that people who switched to SLS-free toothpaste had roughly one fewer ulcer per outbreak cycle, ulcers that healed about two days faster, and significantly less pain. SLS-free toothpastes are widely available and cost about the same as regular options.
Vitamin B12 deficiency is another common contributor. Supplementing with B12 has been shown to reduce canker sore frequency, even in people whose blood levels of B12 appear normal. L-lysine, an amino acid available as a supplement, is another option some people find effective, particularly when sores are triggered by acidic foods. A typical dose is 1,000 mg taken at the first sign of irritation.
When a Sore Needs Attention
Most canker sores are small, less than one millimeter across, round or oval, and heal within a few days to two weeks. A sore larger than one centimeter, one that has irregular or ragged edges, or one that hasn’t healed after two weeks warrants a visit to a doctor or dentist. These features can overlap with more serious conditions, including oral cancer, which looks different from a typical canker sore but can be easy to dismiss early on. A sore that keeps coming back in the exact same spot is also worth getting checked.