Most canker sores heal on their own within 10 to 14 days, but the right combination of home care and topical treatments can reduce pain and speed that timeline. The key is starting treatment early, keeping the area clean, and avoiding irritants that slow healing.
Start With a Rinse
The simplest and cheapest first step is a mouth rinse you can make at home. Dissolve 1 teaspoon of baking soda in half a cup of warm water and swish it around your mouth several times a day, especially after meals. A plain saltwater rinse works too. Both help keep the ulcer clean and create an environment that’s less hospitable to bacteria, which can slow healing or make pain worse.
Rinse gently. Swishing too aggressively can irritate the sore further. You’re aiming to bathe the area, not scrub it.
Over-the-Counter Pain Relief
Topical gels and pastes containing benzocaine are the most widely available option at pharmacies. Benzocaine is a local anesthetic that numbs the surface of the sore on contact, providing temporary relief so you can eat, drink, and talk more comfortably. Apply it directly to the dried sore as directed on the label. These products are meant for short-term use, not weeks of daily application, and should not be used in children under 2.
You can also find OTC protective pastes that form a barrier over the ulcer. These won’t numb the pain as quickly, but they shield the sore from food, drinks, and your teeth, which reduces irritation throughout the day.
Switch Your Toothpaste
This is one of the most overlooked changes you can make. Many standard toothpastes contain sodium lauryl sulfate (SLS), a foaming agent that can irritate the lining of your mouth. In a clinical study, people who switched to an SLS-free toothpaste experienced roughly 60 to 70% fewer canker sores compared to when they used toothpaste containing SLS. If you get canker sores repeatedly, checking your toothpaste ingredient list is worth the two minutes it takes. Several major brands sell SLS-free versions.
Avoid Common Triggers
Certain foods are notorious for either triggering canker sores or making existing ones much more painful. Acidic foods like citrus fruits, tomatoes, and pineapple top the list. Spicy foods, salty snacks, and rough-textured items like chips or crusty bread can also aggravate the sore directly. While you’re healing, stick to softer, blander foods and avoid anything that stings on contact.
Mechanical trauma matters too. Accidentally biting your cheek, brushing too hard, or irritation from braces or ill-fitting dental appliances are common triggers. If you notice your sores tend to appear after dental work or in spots where hardware rubs against your mouth, talk to your dentist about smoothing rough edges or using dental wax as a buffer.
Check for Nutritional Gaps
Recurring canker sores are sometimes a signal that your body is low on certain nutrients, particularly vitamin B12, folate, and iron. B12 deficiency is diagnosed when blood levels fall below 200 pg/mL, and folate deficiency when serum levels drop below 3 ng/mL. You won’t know your levels without a blood test, but if you get canker sores frequently (more than a few times a year), it’s worth asking about screening. Correcting a deficiency, whether through diet or supplements, can reduce how often sores come back.
Foods rich in B12 include meat, fish, eggs, and dairy. Folate is found in leafy greens, legumes, and fortified grains. Iron-rich foods include red meat, beans, and spinach.
When Prescription Treatment Helps
If your canker sores are large, unusually painful, or keep coming back, a doctor or dentist can prescribe stronger options. Topical steroid pastes applied directly to the ulcer several times a day reduce inflammation and can shorten healing time. For more widespread sores covering a larger area of the mouth, a prescription steroid rinse (swished and spit out twice a day) can reach spots that are hard to treat with a paste. One thing to be aware of: steroid rinses can sometimes lead to a secondary fungal infection in the mouth, so your provider will want to monitor you if you’re using one regularly.
Some dental offices also offer laser treatment. The procedure takes about 15 minutes, is virtually painless, and can provide immediate relief from burning and stinging while shortening overall healing time.
How Long Healing Takes
The timeline depends on the type of sore. Minor canker sores, which make up the majority of cases, are under 1 centimeter across and typically heal within 10 to 14 days without scarring. Some mild sores resolve in as little as 2 to 3 days with minimal pain.
Major canker sores are larger than 1 centimeter and behave very differently. They can take up to 6 weeks to fully heal and sometimes leave a scar. These deeper ulcers are the ones most likely to benefit from prescription treatment rather than home care alone.
Some people fall into a pattern of near-constant sores, where a new one forms almost as soon as the last one heals. This pattern warrants a medical evaluation to look for underlying causes like nutritional deficiencies, immune system issues, or other conditions that can mimic canker sores.
When a Canker Sore Needs Medical Attention
Any mouth ulcer that lasts longer than 2 weeks without healing needs professional evaluation. This is a firm threshold. A sore that persists beyond that point, whether painful or not, should be examined to rule out oral cancer, viral or fungal infections, and chronic conditions like lichen planus. This doesn’t mean every lingering sore is dangerous, but a 2-week ulcer that isn’t improving is outside the normal range and deserves a closer look.
Other signs that warrant a visit: sores that are unusually large, sores accompanied by high fever, difficulty swallowing or drinking enough fluids, or new sores appearing before old ones have healed on a regular basis.