Most canker sores heal on their own within 10 to 14 days, but you can speed things up and cut the pain significantly with the right approach. Canker sores (aphthous ulcers) appear inside the mouth, typically on the inner cheeks, inner lips, or tongue. They look like round white or yellow sores with a red border, and they’re not contagious.
Make Sure It’s Actually a Canker Sore
Before treating anything, confirm what you’re dealing with. If the sore is on the outside of your lip, along the border where your lip meets your skin, it’s more likely a cold sore (fever blister). Cold sores start as clusters of small fluid-filled blisters, are caused by the herpes virus, and are contagious. Canker sores appear only inside the mouth, are single ulcers rather than clusters, and aren’t caused by a virus. The treatments for each are completely different, so getting this right matters.
Treatments That Work Fastest
The single most important thing you can do is start treatment early. Over-the-counter gels and pastes work best when applied as soon as the sore appears, ideally during the tingling or slight tenderness stage before it fully opens up.
Look for products containing benzocaine, which numbs the area and reduces pain on contact. Brand names include Anbesol, Kank-A, Orabase, and Zilactin-B. These create a protective film over the sore, shielding it from further irritation while it heals. Apply them directly to the sore several times a day, especially before meals.
Hydrogen peroxide rinses (like Orajel Antiseptic Mouth Sore Rinse) help keep the ulcer clean and can reduce bacteria around the wound. Another simple option: dab a small amount of milk of magnesia directly onto the sore a few times a day. It coats the ulcer and neutralizes acid in your mouth that can aggravate the tissue.
Salt Water Rinses
Dissolve about half a teaspoon of salt in a cup of warm water and swish it around your mouth for 30 seconds, then spit. Do this a few times daily. It won’t taste great, but salt water draws fluid from the swollen tissue, reduces inflammation, and creates an environment that’s harder for bacteria to thrive in. This is free, available immediately, and genuinely helpful.
Honey
Applying honey directly to canker sores has real evidence behind it. A systematic review of 13 studies found that honey reduced the severity or duration of oral ulcers in 12 of them. In one study comparing honey to a standard medicated gel for minor canker sores, both performed equally well for pain reduction and shrinking ulcer size. Dab a small amount of raw honey onto the sore a few times a day. It forms a soothing barrier and has natural antibacterial properties.
When a Sore Won’t Respond to Home Care
If your canker sore hasn’t improved after a week or two of home treatment, prescription options can help. Doctors and dentists can prescribe stronger topical steroids that reduce inflammation more aggressively than anything available over the counter. These come as gels or pastes you apply directly to the sore. They don’t suppress your body’s overall immune system the way oral steroids can, so they’re considered safe for localized use.
Prescription antimicrobial mouth rinses can also reduce pain and the severity of ulceration, though they tend to treat symptoms rather than prevent future outbreaks. For especially painful sores, some providers prescribe a bioadhesive oral gel that physically coats the ulcer and shields exposed nerve endings, providing a protective barrier while you eat and talk.
Reducing Pain While You Heal
Canker sores hurt most when something touches them, so managing your diet makes a big difference. Avoid acidic foods like citrus, tomatoes, and vinegar-based dressings. Spicy foods, crunchy chips, and crusty bread are obvious irritants. Stick to softer, blander foods until the sore closes up. Drinking through a straw can help liquids bypass the sore entirely.
Cold water or ice chips held near the sore can temporarily numb the area. If pain is interfering with eating or sleeping, an over-the-counter pain reliever can help take the edge off.
Why You Keep Getting Them
If canker sores are a recurring problem for you, there’s likely something driving them beyond bad luck. One of the most well-documented triggers is a common ingredient in toothpaste called sodium lauryl sulfate (SLS), a foaming agent. A pooled analysis of clinical trials found that people who switched to SLS-free toothpaste had roughly one fewer ulcer per outbreak, ulcers that healed about two days faster, fewer episodes overall, and significantly less pain. That’s a meaningful improvement from simply changing your toothpaste. Brands like Sensodyne, Biotene, and certain varieties of Tom’s of Maine are SLS-free.
Nutritional deficiencies are another major factor. Low levels of vitamin B12, folate, and iron are all linked to recurrent canker sores. If you’re getting outbreaks two or three times a year or more, it’s worth asking your doctor to check these levels with a simple blood test. B12 deficiency in particular is common and easily treated with daily supplements. Folate deficiency can look similar on lab work but involves different markers, so testing both together gives a clearer picture.
Other known triggers include stress, hormonal changes, minor mouth injuries (like biting your cheek or aggressive brushing), and certain food sensitivities. Keeping a rough log of when outbreaks happen can help you identify your personal pattern.
Minor vs. Major Canker Sores
Most canker sores are minor, meaning they’re small (under a centimeter), shallow, and heal within 10 to 14 days without scarring. Major canker sores are larger, deeper, and can last up to a month. They sometimes leave scars and are significantly more painful. If your sore is bigger than a pea, lasts longer than two weeks, comes with fever or flu-like symptoms, or makes it difficult to eat or drink, that crosses the line from a nuisance into something that warrants professional evaluation. The same goes for sores that keep coming back several times a year, since that pattern can signal an underlying nutritional deficiency or immune issue worth investigating.