Most canker sores heal on their own within 10 to 14 days, but the right treatment can cut down pain significantly and speed things along. What works best depends on how severe the sore is: minor cases respond well to simple home rinses and over-the-counter products, while larger or recurring sores sometimes need prescription-strength treatment.
Salt Water and Baking Soda Rinses
The simplest and cheapest treatment is a mouth rinse you can mix at home. Combine 1 teaspoon of salt and 1 teaspoon of baking soda in 1 quart (4 cups) of water. Rinse your mouth with this solution every 4 to 6 hours, or more often if the pain is bothering you. You can also use just salt or just baking soda if you prefer. The salt helps draw fluid out of the sore to reduce swelling, while baking soda neutralizes acids in your mouth that irritate the open tissue.
This rinse won’t numb the pain instantly, but it creates a cleaner environment for healing and keeps the sore from getting worse. Many people find that consistent rinsing, especially after meals, makes a noticeable difference within the first day or two.
Over-the-Counter Pain Relief
For more immediate relief, topical numbing products containing benzocaine are widely available as gels, sprays, and ointments. You apply them directly to the sore up to 4 times a day, and they temporarily block pain signals from the area. These products shouldn’t be used for more than 2 days in a row without checking with a doctor, so they’re best reserved for the worst of the pain rather than used throughout the entire healing process.
Protective pastes that form a barrier over the sore are another option. These coat the ulcer so food, drinks, and your teeth don’t keep aggravating it. Some combine a numbing agent with the protective layer, which gives you both pain relief and a physical shield. Look for products specifically labeled for mouth sores rather than general oral care.
Prescription Treatments for Severe Sores
If your canker sore is large, unusually painful, or keeps coming back, a dentist or doctor can prescribe a steroid paste. These pastes reduce the inflammation driving the pain and swelling. You apply a small amount to the sore after meals and at bedtime, pressing it gently with a cotton swab to form a thin film. The key is not to rub it in. Rubbing makes the paste crumbly and prevents it from sticking properly.
For widespread or frequently recurring sores, a prescription steroid mouthwash is sometimes used instead. This lets you treat multiple sores at once or reach spots that are hard to dab with a paste.
How Long Healing Takes
The timeline depends on what type of canker sore you’re dealing with. Most people get minor canker sores, which are small (under a centimeter), shallow, and round or oval. These typically clear up in 10 to 14 days without treatment, and faster with it.
Major canker sores are larger, deeper, and significantly more painful. These can last up to a month and sometimes leave a scar. They’re less common but more likely to need prescription treatment. A third type, called herpetiform ulcers, appears as clusters of tiny sores that can persist anywhere from 10 to 100 days. Despite the name, these aren’t caused by the herpes virus.
Preventing Canker Sores From Coming Back
If you get canker sores regularly, your toothpaste might be part of the problem. Sodium lauryl sulfate (SLS), a foaming agent found in most major toothpaste brands, is a known soft tissue irritant. It’s the same compound used in shampoos and household cleaners. Switching to an SLS-free toothpaste is one of the easiest changes you can make, and for some people it dramatically reduces how often sores appear.
Nutritional deficiencies also play a role. Low levels of B12, iron, and folate are linked to recurrent canker sores. One clinical trial tested 1,000 micrograms of sublingual vitamin B12 taken daily at bedtime for six months and found it reduced outbreaks. If your sores keep returning, it’s worth having your levels checked. Other common triggers include acidic or spicy foods, physical trauma from braces or biting your cheek, and periods of high stress or poor sleep.
Signs a Canker Sore Needs Medical Attention
A single small canker sore that heals within two weeks is nothing to worry about. But sores that make eating or drinking difficult, that recur frequently, or that persist well beyond two weeks deserve a closer look. Canker sores that are unusually large, appear in clusters, or come with fever or swollen lymph nodes can occasionally signal an underlying condition like an immune disorder or nutritional deficiency that needs to be identified and treated separately.