Most canker sores heal on their own within two weeks, but the pain peaks in the first few days, which is exactly when you need relief. The good news: a combination of simple home rinses, over-the-counter numbing agents, and smart food choices can take the edge off and help the sore heal faster.
Salt Water and Baking Soda Rinses
The simplest and cheapest option is a rinse you can make right now. Dissolve one teaspoon of baking soda in half a cup of warm water, swish gently for 30 seconds, and spit. A salt water rinse works the same way: roughly half a teaspoon of table salt in the same amount of warm water. Both help reduce bacteria around the sore and create a less acidic environment in your mouth, which eases irritation. You can repeat these rinses several times a day, especially after meals.
Over-the-Counter Numbing Products
Benzocaine is the active ingredient in most OTC canker sore gels, ointments, and sprays. It works as a local anesthetic, temporarily blocking pain signals from the sore’s surface. You apply it directly to the ulcer up to four times a day, and relief kicks in within a minute or two. It comes in gels, pastes, swabs, and even lozenges that dissolve slowly in your mouth.
A few practical tips: dry the sore gently with a tissue before applying a gel or paste so it sticks better. Try to avoid eating or drinking for at least 15 minutes afterward. Don’t use benzocaine products for more than two consecutive days without checking with a dentist or doctor, as prolonged use can cause its own irritation.
Protective pastes that form a barrier over the sore are another option. These don’t numb the area but shield it from food, drinks, and your teeth, which can make eating much more comfortable.
Foods That Make It Worse
What you eat matters as much as what you put on the sore. Acidic foods and drinks lower the pH inside your mouth, breaking down the protective layer of tissue and making the ulcer sting. The obvious culprits are citrus fruits, fizzy drinks, and alcohol. Less obvious ones include strawberries and tomatoes, which are acidic enough to trigger pain even though they don’t taste sour.
Spicy and salty foods irritate the delicate lining of your mouth directly, so dial those back until the sore closes. Texture also plays a role. Hard, crunchy, or sharp foods like crusty bread, chips, and crackers can physically scrape the ulcer and set back healing. Stick to softer foods: yogurt, scrambled eggs, oatmeal, mashed potatoes, smoothies. If you eat something warm, let it cool slightly first, since heat intensifies the sting.
Check Your Toothpaste
If you get canker sores repeatedly, your toothpaste might be part of the problem. Many standard toothpastes contain sodium lauryl sulfate (SLS), a foaming detergent that helps clean your teeth but can disrupt the soft tissue inside your mouth. Research has found that switching to an SLS-free toothpaste reduced the number, pain, and recurrence of mouth ulcers. Most SLS-free options are easy to find at drugstores or online. Check the inactive ingredients list on your current tube.
Nutrient Deficiencies and Recurring Sores
A canker sore once or twice a year is normal. But if you get them frequently, low levels of certain nutrients may be a factor. Studies on people with recurrent canker sores consistently find higher rates of vitamin B12, iron, and folate deficiency compared to people who rarely get them. In one study, 73% of patients with B12 deficiency saw their ulcers resolve completely after B12 supplementation, and about 70% of patients improved with targeted nutrient replacement overall.
This doesn’t mean you should start megadosing vitamins. It does mean that if you’re dealing with sores every month or two, a blood test checking B12, ferritin (your iron stores), and folate levels is worth requesting. Vegetarians, vegans, people with digestive conditions, and anyone with a restricted diet are at higher risk for these deficiencies.
What the Healing Timeline Looks Like
Most canker sores are minor, meaning they’re small, round or oval, and shallow. Pain tends to be worst during the first two to four days. After that, the sting gradually fades even if the sore is still visible. The ulcer itself typically closes within one to two weeks without leaving a scar.
Major canker sores are deeper, larger, and far less common. These can take weeks or even months to fully heal and sometimes leave scarring. A third type, called herpetiform canker sores, appears as clusters of tiny ulcers that merge together but usually heals within about two weeks.
Canker Sores vs. Cold Sores
These two get confused constantly, but they’re different conditions. Canker sores are white or yellow ulcers that form only inside the mouth, on the inner cheeks, lips, tongue, or gums. They are not caused by a virus and are not contagious. Cold sores (fever blisters) are fluid-filled blisters caused by the herpes simplex virus, and they form on the outside of the mouth, typically along the border of the lips. The easiest way to tell them apart is location: inside the mouth means canker sore, outside means cold sore. The treatments are completely different, so getting this right matters.
When a Canker Sore Needs Attention
Most canker sores don’t need professional treatment. But a sore that hasn’t healed after two weeks, keeps growing larger, comes with a high fever, or makes it genuinely difficult to drink fluids is worth having a dentist or doctor examine. The same goes for sores that keep coming back in clusters. Prescription options exist for stubborn or severe cases, including steroid rinses and stronger topical treatments that reduce inflammation more aggressively than anything available over the counter.