Most canker sores heal on their own within two weeks, but several treatments can cut that time roughly in half and reduce pain significantly along the way. The key is managing inflammation, keeping the sore clean, and avoiding irritants that slow your body’s natural repair process.
How Canker Sores Heal on Their Own
Your body treats a canker sore like any other wound. Inflammation peaks in the first few days, which is when pain is worst, then new tissue gradually covers the open ulcer from the edges inward. Minor canker sores, the most common type, are smaller than a centimeter across and typically close up within one to two weeks without scarring.
Major canker sores are a different story. These are larger than a centimeter, significantly more painful, and can take months to fully heal. They often leave scars. A third, rarer type called herpetiform canker sores appears as clusters of tiny pinpoint ulcers that usually resolve in about two weeks.
Pain tends to improve within three to five days regardless of what you do. The ulcer itself takes longer to disappear, but most of the misery is front-loaded.
Home Remedies That Actually Help
A saltwater or baking soda rinse is the simplest first step. Dissolve about half a teaspoon of salt or baking soda in a cup of warm water and swish gently for 30 seconds a few times a day. The alkaline environment reduces mouth acid and irritation around the sore, creating better conditions for healing. It won’t dramatically speed things up, but it keeps the area clean and makes eating less painful.
Avoiding certain foods matters more than most people realize. Acidic foods like tomatoes, citrus, and vinegar-based dressings directly irritate the exposed tissue. Crunchy or sharp-edged foods like chips and crackers can physically reopen the wound. Sticking to softer, blander foods for a few days lets the sore close faster.
Over-the-Counter Treatments
Numbing gels and pastes containing benzocaine are widely available at pharmacies and work by temporarily blocking pain signals at the sore’s surface. They don’t accelerate healing, but they make eating and talking bearable while your body does the repair work. Apply them directly to the sore before meals for the best effect.
Antiseptic mouth rinses containing chlorhexidine can reduce the severity and pain of ulcers, though they don’t prevent new ones from forming. Adhesive oral patches that stick over the sore create a protective barrier, shielding it from food and saliva while delivering medication. These tend to work best on sores in easy-to-reach spots like the inner lip.
Switching Your Toothpaste
If you get canker sores repeatedly, your toothpaste may be part of the problem. Sodium lauryl sulfate (SLS), the foaming agent in most toothpastes, is a known trigger for recurrent canker sores. About 60% of people prone to mouth ulcers saw improvement after switching to an SLS-free toothpaste. One controlled trial found that toothpaste with SLS caused tissue irritation and sloughing in 60% of participants, while SLS-free versions caused no reaction at all.
SLS-free toothpastes are easy to find at most drugstores. This single change won’t eliminate canker sores for everyone, but for people who get them frequently, it’s one of the most effective and simplest prevention strategies available.
Prescription Options for Stubborn Sores
When a canker sore is large, unusually painful, or slow to heal, prescription-strength topical steroids can help. These work by dialing down the inflammatory response, reducing swelling and pain at the site. They come as gels, pastes, or rinses that you apply directly to the sore. Topical steroids used in the mouth at these doses don’t carry the systemic side effects people associate with long-term steroid use.
For sores that don’t respond to topical treatment, a dentist or doctor can perform chemical cauterization using silver nitrate. In one clinical study, 60% of patients who received silver nitrate cauterization had completely healed ulcers by day seven, compared to 32% in the untreated group. The average healing time after cauterization was just 2.7 days, versus 5.5 days without it. Pain dropped immediately after the procedure, and no side effects were recorded.
Low-level laser therapy is another in-office option gaining traction. In clinical studies, 75% of patients reported pain reduction during the same session, and lesions healed completely within three to four days, slightly faster than with steroid treatment alone. Not every dental office offers this, but it’s worth asking about if you deal with frequent or severe outbreaks.
Nutrient Deficiencies and Recurring Sores
People who get canker sores over and over sometimes have an underlying nutritional gap driving the cycle. Low levels of vitamin B12, iron, folate, and zinc are all linked to higher rates of recurrent canker sores. This connection is strong enough that if you’re getting sores every few weeks or months, it’s worth having your levels checked through a simple blood test.
Correcting a deficiency through diet or supplements can reduce how often sores appear. Iron-rich foods like red meat, lentils, and spinach, along with B12 from meat, eggs, and dairy, cover the most common gaps. For people on plant-based diets, B12 supplementation is especially relevant since that vitamin is almost exclusively found in animal products.
Other Common Triggers
Beyond nutrient levels and toothpaste, several other factors can set off canker sores or make them worse. Stress is one of the most consistent triggers, likely because it suppresses immune function in the mouth’s mucous membranes. Hormonal shifts, particularly around menstruation, are another well-documented pattern. Minor mouth injuries from braces, dental work, or accidentally biting your cheek can also spark a sore in the damaged spot.
Keeping a simple log of when sores appear and what preceded them can help you identify your personal triggers. Some people notice a clear pattern with certain foods, stress levels, or points in their menstrual cycle. Once you know what sets yours off, you can take targeted steps to reduce frequency rather than just treating each sore as it comes.
When a Canker Sore Needs Professional Attention
Any oral ulcer lasting more than two weeks warrants a professional evaluation. At that point, it may not be a simple canker sore, and conditions like oral lichen planus or, rarely, oral cancer can look similar. Sores larger than a centimeter, sores that come with fever, or outbreaks so frequent they overlap are also signals that something beyond a routine canker sore is going on. A dentist or oral medicine specialist can rule out other causes and, if needed, prescribe stronger treatments to break the cycle.