Most canker sores heal on their own within two weeks, but you can cut that time shorter and dramatically reduce pain by acting fast. The single most important factor is timing: treatments work best when applied at the first tingle or within the first day of the sore appearing. Here’s what actually works, ranked roughly by how quickly you’ll feel a difference.
Start With What You Have at Home
A salt water or baking soda rinse is the fastest thing you can do right now, with no trip to the store. Dissolve 1 teaspoon of baking soda in half a cup of warm water and swish it around the sore for 30 seconds. This neutralizes acids in your mouth that irritate the ulcer and creates an environment that helps tissue repair. You can repeat this several times a day.
Ice works surprisingly well for immediate pain. Let a small ice chip rest directly on the sore until it dissolves. This won’t speed healing, but it numbs the area and reduces inflammation so you can eat and talk without wincing. Dabbing a small amount of milk of magnesia directly onto the sore a few times a day also coats and soothes it.
Over-the-Counter Products That Speed Healing
If the sore is already fully formed and painful, a topical product with benzocaine (sold under names like Anbesol, Orabase, and Zilactin-B) gives near-instant numbing relief. Apply it directly to the sore as needed. It won’t make the ulcer disappear overnight, but it blocks pain on contact so you can get through the day.
Hydrogen peroxide rinses, like Orajel Antiseptic Mouth Sore Rinse, serve a different purpose. They clean the ulcer and reduce bacteria in the area, which helps prevent the sore from getting worse and supports faster tissue repair. You can also make your own by mixing equal parts 3% hydrogen peroxide and water, then dabbing it on the sore with a cotton swab.
For the best results, combine approaches: rinse with baking soda water first to clean the area, then apply a numbing gel or protective paste directly to the sore. Products that form a coating over the ulcer, like oral adhesive pastes, act as a physical barrier between the sore and everything in your mouth. That barrier protects the wound from friction caused by food, teeth, and your tongue, which is one of the main reasons canker sores take so long to heal. Researchers at Texas A&M have been developing bioadhesive patches specifically designed to shield ulcers from physical irritation while delivering medication directly to the wound site.
Prescription Options for Severe Sores
When a canker sore is large, extremely painful, or not responding to over-the-counter treatments, a doctor or dentist can prescribe a steroid gel such as fluocinonide. These reduce the inflammatory response that causes much of the pain and swelling, and they can significantly shorten healing time when applied early.
For sores that are truly disrupting your life, some dental offices offer laser therapy or cauterization. These procedures destroy the nerve endings at the surface of the ulcer, which can eliminate pain almost immediately and speed up healing by clearing bacteria from the area. This is typically reserved for large or recurring sores, but it’s worth asking about if you get them frequently.
What to Avoid While It Heals
Everything you put in your mouth either helps or hurts. Acidic foods like tomatoes, citrus, and coffee directly irritate the open tissue and can make the sore larger. Spicy foods, crunchy chips, and anything with sharp edges (looking at you, tortilla chips) cause mechanical damage to the ulcer. Stick to soft, bland, cool foods until the sore closes up.
Check your toothpaste label for sodium lauryl sulfate, often listed as SLS. This foaming agent strips away the protective mucus layer inside your mouth, leaving tissue vulnerable to damage. A 2019 systematic review of four clinical trials found that switching to SLS-free toothpaste significantly reduced the number of ulcers, how long each one lasted, and how much pain they caused. One earlier study found a 64% reduction in canker sores simply from changing toothpaste, dropping from an average of 14.3 ulcers over three months to just 5.1. If you get canker sores regularly, this is one of the easiest and most effective changes you can make.
Why Some People Get Them Repeatedly
If canker sores keep coming back, the cause is often nutritional rather than something you’re doing wrong. Vitamin B12 deficiency is strongly linked to recurrent mouth ulcers. One study found that over 50% of patients with recurring canker sores were deficient in B12, compared to none in the control group. When those deficient patients received B12 supplementation, 73% recovered completely. Iron deficiency may also play a role, though the evidence is less consistent.
Stress is the other major trigger. Physical and emotional stress suppresses immune function in the tissues lining your mouth, making ulcers more likely to form. You can’t always control stress, but recognizing the pattern helps you act early. If you notice the telltale tingle or bump forming during a stressful week, starting treatment immediately rather than waiting gives you the best chance of keeping it small and short-lived.
When a Sore Needs Professional Attention
A typical canker sore is a round or oval white or yellowish ulcer with a red border, and it hurts. It should start improving noticeably within a week and be gone within two. If a mouth sore lingers beyond that, it’s worth having it looked at. Red, white, or mottled patches that don’t heal, a bump under the skin beneath the ulcer, or sores that are unusually large or keep recurring more severely than usual all warrant a visit to your primary care provider or dentist. These are rarely anything serious, but a persistent sore that doesn’t follow the normal healing pattern should be evaluated to rule out other conditions.