Most canker sores heal on their own within 10 to 14 days, but the right care can reduce pain and may shorten that timeline by a few days. These small, round ulcers form inside the mouth on soft tissue like the inner cheeks, gums, or tongue, and while they’re not dangerous, they can make eating and talking miserable in the meantime.
What Actually Causes Canker Sores
The exact cause isn’t fully understood, but canker sores appear to be driven by your own immune system. Certain immune cells attack and break down the lining of the mouth, and the damage is sustained by a local release of inflammatory signals. People who get canker sores frequently show signs of an overactive inflammatory response in the mouth’s soft tissue.
Common triggers include minor injuries (biting your cheek, aggressive brushing, sharp food), stress, hormonal changes, certain acidic or spicy foods, and nutritional deficiencies in iron, zinc, folate, or B vitamins. Sodium lauryl sulfate, a foaming agent in many toothpastes, is another well-known trigger for some people. Canker sores are not contagious and are not caused by a virus, which is what separates them from cold sores.
Home Remedies That Help
Salt Water and Baking Soda Rinses
A simple rinse is the most accessible first step. Dissolve 1 teaspoon of baking soda in half a cup of warm water and swish gently for 30 seconds, then spit. You can also use a half teaspoon of salt in the same amount of water. Either rinse helps reduce bacteria around the ulcer and creates an environment that supports healing. Do this several times a day, especially after meals.
Honey
Applying a small amount of honey directly to the sore three times a day is a well-studied alternative. In clinical comparisons, honey performed about as well as standard medicated gels for both pain reduction and ulcer size, with no reported side effects. Raw, unprocessed honey tends to be recommended. It coats the sore, provides a mild antibacterial layer, and many people find it more pleasant than chemical treatments.
Avoiding Irritants
What you stop doing matters as much as what you start doing. Avoid crunchy, acidic, or spicy foods that scrape or sting the sore. Tomatoes, citrus, vinegar-based dressings, and chips are common offenders. If your toothpaste contains sodium lauryl sulfate, switching to an SLS-free brand can help the current sore heal faster and may prevent future ones.
Over-the-Counter Treatments
Benzocaine products (typically at a 20% concentration) are the most widely available OTC option for canker sore pain. Applied directly to the ulcer, benzocaine numbs the area for temporary relief, which is especially useful before meals. You’ll find it in gels, ointments, and patches sold specifically for mouth sores. The numbing effect wears off after 15 to 30 minutes, so you may need to reapply.
Protective pastes and films are another category worth trying. These products form a barrier over the sore, shielding it from food, saliva, and friction. Some combine a protective coating with a pain reliever. Covering the ulcer this way can make eating significantly more comfortable and may speed healing by preventing repeated irritation.
Antiseptic mouth rinses containing hydrogen peroxide (diluted) can also help keep the area clean. Look for rinses specifically labeled for mouth sores rather than using full-strength hydrogen peroxide, which can irritate healthy tissue.
Prescription Options for Severe Sores
If your canker sore is unusually large, extremely painful, or keeps coming back, prescription treatments go a step further. Topical steroid pastes and creams are the main approach. These are applied directly to the sore several times a day for about two weeks and work by calming the overactive immune response that’s damaging the tissue. Starting a steroid paste early, ideally when you first feel the tingling or tenderness that signals a sore is forming, gives the best results.
For major canker sores (the kind that can last up to a month and leave scars), a dentist or doctor may offer a steroid injection directly into the sore to speed healing. This is reserved for sores that are seriously interfering with eating or speaking.
Canker Sore vs. Cold Sore
These two get confused constantly, but they’re completely different conditions with different treatments. The quickest way to tell them apart:
- Location: Canker sores form inside the mouth. Cold sores (fever blisters) form outside the mouth, usually around the border of the lips.
- Appearance: A canker sore is typically a single round white or yellow sore with a red border. A cold sore is a cluster of small, fluid-filled blisters.
- Cause: Cold sores are caused by herpes simplex virus type 1 and are contagious. Canker sores have no known viral cause and cannot be spread to another person.
This distinction matters because antiviral creams designed for cold sores won’t help a canker sore, and the immune-calming treatments for canker sores aren’t appropriate for an active viral infection.
How Long Each Type Takes to Heal
Not all canker sores are the same size or severity, and the type you have determines how long you’ll be dealing with it. Minor canker sores, which account for the majority of cases, are small (under a centimeter) and heal in about 10 to 14 days without treatment. They don’t leave scars.
Major canker sores are deeper, larger, and significantly more painful. These can take up to a month to fully heal and sometimes leave scar tissue behind. A third, less common type called herpetiform ulcers appears as clusters of tiny sores that can merge into larger, irregular ulcers. Despite the name, these aren’t caused by herpes. They can persist anywhere from 10 to 100 days and make eating and speaking extremely difficult.
Signs a Sore Needs Professional Attention
A typical canker sore, while painful, resolves on its own and doesn’t need medical evaluation. But certain patterns warrant a visit to your dentist or doctor: sores that last longer than three weeks, sores that are unusually large or deep, sores that spread or appear in clusters you’ve never experienced before, sores accompanied by a high fever, or frequent recurrences (several times a year). Persistent ulcers that don’t heal on a normal timeline occasionally need a biopsy to rule out other conditions, including oral cancer, especially in people over 40 or those who use tobacco.
Preventing the Next One
If you’re prone to canker sores, small habit changes can reduce how often they appear. Switch to an SLS-free toothpaste, since this single change eliminates a common trigger. Use a soft-bristled toothbrush and brush gently to avoid micro-injuries to the lining of your mouth. Address nutritional gaps: a daily multivitamin with B12, folate, iron, and zinc covers the most commonly implicated deficiencies.
Keep a loose mental log of what you ate or what was happening before an outbreak. Many people notice patterns with specific foods (walnuts, chocolate, strawberries, and cheese are frequent culprits) or with periods of stress and poor sleep. Identifying your personal triggers is the most effective long-term prevention strategy, since the underlying immune mechanism can’t be “cured” but its triggers can often be managed.