Most canker sores heal on their own within one to two weeks, but you can speed up the process and cut the pain significantly with the right approach. What works best depends on the size of the sore and how much it’s bothering you, ranging from simple rinses you can make at home to over-the-counter numbing gels and, for stubborn cases, prescription treatments.
How Long Canker Sores Take to Heal
Not all canker sores are the same, and knowing which type you’re dealing with helps set realistic expectations. Minor canker sores, the most common kind, are smaller than a pea (under one centimeter across). These heal within a few weeks and don’t leave scars. Most people who search for relief are dealing with this type.
Major canker sores are larger than one centimeter, extremely painful, and can take months to heal. They often leave scars. Herpetiform canker sores look different altogether: clusters of tiny pinpoint ulcers that tend to heal within about two weeks without scarring. If your sore hasn’t healed after two weeks, or if it’s unusually large, that’s a signal to get it evaluated by a doctor or dentist.
Home Remedies That Actually Help
A saltwater rinse is the simplest first step. Dissolve about half a teaspoon of salt in a cup of warm water and swish it around the sore for 30 seconds before spitting it out. This reduces bacteria around the ulcer and draws out some of the fluid causing swelling. It will sting briefly, but the discomfort eases quickly.
Hydrogen peroxide is another effective option for keeping the sore clean. Use a 3% solution (the standard concentration sold in drugstores) diluted with equal parts water. You can dab it directly onto the sore with a cotton swab or use it as a gentle mouth rinse. Don’t swallow it, and don’t use it undiluted, as full-strength peroxide can irritate the surrounding tissue.
Applying a small amount of milk of magnesia directly to the sore several times a day can coat and soothe it. Some people alternate this with the hydrogen peroxide rinse: clean with diluted peroxide first, then coat with milk of magnesia afterward. Ice chips held against the sore can also temporarily numb the area and reduce inflammation, which is especially useful right before eating.
Over-the-Counter Products Worth Trying
Benzocaine gels and pastes are the most widely used OTC treatment for canker sore pain. Products like Orajel and Anbesol contain benzocaine at concentrations between 5% and 20%, which numbs the nerve endings on contact. Apply a thin layer directly to the sore before meals or whenever the pain flares. The relief is temporary, usually lasting 15 to 30 minutes, but it makes eating and drinking far more manageable.
Protective pastes that contain ingredients like carboxymethylcellulose work differently. Rather than numbing, they form a barrier over the sore that shields it from food, drinks, and your teeth. These are especially helpful if the sore is in a spot that keeps getting irritated, like the inside of your lip or the edge of your tongue. Some products combine both a numbing agent and a protective barrier in one formula.
Antimicrobial rinses containing cetylpyridinium chloride or chlorhexidine can help prevent secondary infection that slows healing. These won’t eliminate the sore on their own, but they keep the wound environment cleaner so your body can repair the tissue faster.
When You Need Something Stronger
For canker sores that are large, recurring, or interfering with eating and speaking, a doctor or dentist can prescribe a steroid mouth rinse. These rinses reduce the inflammation driving the pain and swelling, and they can shorten healing time noticeably. You typically swish the solution for about a minute after meals and before bed, then spit it out and avoid eating or drinking for 30 minutes.
Another option your dentist may offer is chemical cauterization with silver nitrate. A study comparing this approach to a placebo found that 60% of treated sores were completely healed by day seven, compared to just 32% of untreated sores. Patients in the treatment group reported an average healing time of about 2.7 days after the procedure, and pain scores were significantly lower starting from the first day. The procedure itself takes seconds: the dentist touches a silver nitrate stick to the sore, which destroys the damaged nerve endings on the surface. It stings intensely for a moment, then the pain drops sharply.
What Causes Canker Sores in the First Place
Canker sores aren’t contagious and aren’t caused by a virus (that’s cold sores, which appear on the outside of the lips). The exact trigger varies from person to person, but common culprits include minor mouth injuries from biting your cheek or aggressive brushing, stress, hormonal shifts, and certain foods. Acidic or spicy foods like citrus, tomatoes, and hot peppers are frequent offenders.
Nutritional deficiencies play a role for some people. Research on patients with recurrent canker sores found iron deficiency in about 20% of cases, anemia in roughly 21%, and smaller percentages with low levels of B12 and folate. If you get canker sores frequently, especially more than three or four times a year, it’s worth asking your doctor to check these levels with a simple blood test. Correcting a deficiency can reduce how often sores come back.
Preventing Recurrences
You may have heard that switching to a toothpaste without sodium lauryl sulfate (SLS), a foaming agent in most toothpastes, helps prevent canker sores. The evidence on this is weak. A 2019 review found there wasn’t enough data to confirm that SLS-free toothpastes reduce how often sores appear, how long they last, or how much they hurt. A double-blind study found no significant change in ulcer patterns after switching. That said, some people report subjective improvement, and SLS-free toothpastes are inexpensive, so trying one carries little downside.
What does help is avoiding known triggers. Keep a mental note of what you ate or what was going on in the day or two before a sore appeared. Over time, patterns emerge. If citrus fruits or certain spices consistently precede an outbreak, cutting back is the most effective prevention you have. Using a soft-bristled toothbrush and being gentler when brushing reduces the minor tissue injuries that can set off a sore. Managing stress, while easier said than done, also correlates with fewer recurrences for many people.
For people who get severe or frequent outbreaks despite lifestyle adjustments, a doctor can prescribe daily supplements or low-dose medications aimed at suppressing the immune response that creates the ulcers. This level of management is reserved for cases where sores are genuinely disruptive, appearing multiple times a month or lasting far longer than the typical two-week window.