Most canker sores heal on their own within one to two weeks, but you can speed that process and cut the pain significantly with the right combination of rinses, topical treatments, and dietary changes. The key is acting fast: treatments work best when applied as soon as a sore appears.
Why Canker Sores Form
Canker sores (aphthous ulcers) are not fully understood, but they appear to involve an overactive immune response in people with a genetic predisposition. Your immune system’s T cells attack the lining of your mouth, creating those shallow, painful craters on the inner cheeks, lips, tongue, or soft palate. They are not contagious and are not caused by a virus (that’s cold sores, which are different).
Common triggers include:
- Mouth trauma: biting your cheek, aggressive brushing, or irritation from braces or dental appliances
- Stress: outbreaks spike during exam periods and high-pressure stretches
- Nutritional deficiencies: low iron, B1, B2, or B6 levels are found in roughly 28% of people with recurring canker sores
- Hormonal shifts: some women get sores tied to the luteal phase of their menstrual cycle, with improvement during pregnancy
- Food sensitivities: reactions to cow’s milk and other allergens can trigger outbreaks in some people
- Quitting smoking: paradoxically, stopping smoking can trigger or worsen canker sores in some cases
Home Rinses That Actually Help
A saltwater rinse is the simplest and cheapest first step. Mix about half a teaspoon of salt into a cup of warm water, swish for 30 seconds, and spit. This draws fluid out of the sore, temporarily reducing swelling and creating a less hospitable environment for bacteria. You can repeat this several times a day.
Another effective option is a hydrogen peroxide rinse. Mix equal parts 3% hydrogen peroxide and water, swish gently, and spit (don’t swallow). For a more targeted approach, dab the mixture directly onto the sore with a cotton swab, then follow with a small dab of milk of magnesia. You can do this up to four times a day.
Over-the-Counter Treatments
OTC products come as pastes, gels, creams, and liquids. The most widely available contain benzocaine, a numbing agent found in products like Anbesol, Orabase, and Zilactin-B. These won’t make the sore heal faster, but they block pain for up to a few hours per application, which makes eating and talking bearable.
For best results, gently pat the sore dry with a tissue or gauze before applying any topical product. Moisture on the surface keeps gels and pastes from sticking, so they wash off within minutes instead of forming a protective layer. Apply the product right after drying, press gently, and avoid eating or drinking for at least 15 to 20 minutes afterward.
Hydrogen peroxide rinses designed for mouth sores (like Peroxyl) are also available over the counter and serve a dual role: mild antiseptic action plus some soothing relief.
Prescription Options for Severe Sores
If OTC products aren’t cutting it, a dentist or doctor can prescribe stronger options. A steroid gel containing fluocinonide reduces inflammation directly at the sore, which both eases pain and promotes faster healing.
For stubborn or especially painful sores, there’s a chemical cauterizing agent called Debacterol. It contains sulfonated phenolics and sulfuric acid, which sounds intense, and it is. A healthcare provider (or you, with a prescription) rolls the applicator across the dried sore for 5 to 10 seconds. It stings immediately on contact, but after rinsing with water, the treated tissue is sealed. One application per sore is usually enough. If pain returns shortly after rinsing, it typically means part of the ulcer wasn’t fully covered, and one repeat application can finish the job.
Switch to SLS-Free Toothpaste
Sodium lauryl sulfate (SLS) is the foaming agent in most toothpastes, and it irritates the mouth lining in people prone to canker sores. A meta-analysis of randomized controlled trials found that switching to SLS-free toothpaste reduced the number of ulcers by about one per cycle, shortened healing time by roughly two days per sore, and significantly reduced pain scores. The number of episodes dropped as well.
If you get canker sores more than a few times a year, switching toothpaste is one of the easiest and most evidence-backed changes you can make. Brands like Sensodyne, Biotene, and Verve all make SLS-free options, though you’ll need to check the label since not every product in a brand’s lineup is SLS-free.
Foods to Avoid While Healing
What you eat matters more than most people realize when a sore is active. Certain foods physically burn, sting, or scrape the ulcer, which resets the healing clock.
Acidic foods are the biggest offenders: citrus fruits, tomatoes, pineapple, berries, vinegar, coffee, fruit juice, and alcohol all cause a stinging or burning sensation and can delay tissue repair. Spicy foods containing capsaicin (hot sauce, curry, chili powder, salsa, sriracha) irritate the exposed nerve endings in the sore. Hard, crunchy foods like chips, pretzels, popcorn, crusty bread, granola, and crackers can physically scrape the ulcer open again.
Stick to soft, cool, bland foods while you’re healing. Yogurt, oatmeal, scrambled eggs, mashed potatoes, smoothies (skip the acidic fruit), and lukewarm soups are all safe choices.
Prevent Recurring Outbreaks
If you get canker sores regularly, addressing the underlying triggers makes a bigger difference than treating each sore individually. Start by switching to SLS-free toothpaste and using a soft-bristled toothbrush to minimize mouth trauma. If you wear braces or a retainer, orthodontic wax on sharp edges can prevent the friction that starts many sores.
Nutritional gaps are worth investigating. About 28% of people with recurrent canker sores have deficiencies in one or more B vitamins, and low iron levels are another common finding. A simple blood test can identify these, and supplementation or dietary changes often reduce outbreak frequency. Good dietary sources of B vitamins include whole grains, eggs, legumes, and leafy greens. Iron-rich foods include red meat, lentils, and spinach.
Keep a food diary if you suspect certain foods trigger your outbreaks. Common culprits beyond the obvious acidic and spicy categories include chocolate, nuts, and wheat, though triggers vary widely from person to person.
When a Canker Sore Signals Something Else
A typical canker sore is small, round, shallow, and heals within two weeks. Sores that don’t follow that pattern deserve medical attention. Specifically, watch for sores that last longer than three weeks, are unusually large (bigger than a centimeter across), come in frequent clusters, spread to the lips or skin outside the mouth, or are accompanied by fever, joint pain, or eye inflammation.
Recurrent, painful mouth ulcers that appear alongside genital ulcers or eye problems can be an early sign of Behçet syndrome, an inflammatory condition affecting blood vessels throughout the body. Persistent oral ulcers with deep, linear patterns, lip swelling, or a cobblestone texture to the inner cheeks can indicate Crohn’s disease. In both conditions, mouth sores are sometimes the very first symptom to appear, showing up before any digestive or systemic problems become obvious. Widespread, easily ruptured blisters inside the mouth can point to pemphigus vulgaris, an autoimmune blistering disease that needs prompt treatment.