Most canker sores heal on their own within one to two weeks, but you can significantly reduce the pain and speed things along with a few simple treatments. The key is starting early: applying a topical product or rinse as soon as the sore appears makes the biggest difference in both comfort and healing time.
Quick Pain Relief at Home
A saltwater rinse is the simplest first step. Mix about half a teaspoon of salt into a cup of warm water, swish it around your mouth for 30 seconds, and spit. This draws fluid out of the inflamed tissue, temporarily reducing swelling and pain. You can repeat this several times a day. Baking soda dissolved in water works similarly and helps neutralize acids in your mouth that irritate the sore.
For more targeted relief, dab a mixture of equal parts water and hydrogen peroxide directly onto the sore with a cotton swab. Follow that with a small amount of milk of magnesia on top. You can repeat this routine up to four times a day. The peroxide helps keep the area clean while the milk of magnesia coats and soothes the surface.
Avoiding certain foods also makes a real difference. Acidic fruits like oranges and tomatoes, spicy dishes, and crunchy or sharp-edged foods (chips, crusty bread) all scrape against or chemically irritate the open sore. Stick to softer, blander foods until the worst of the pain passes, usually within the first four to five days.
Over-the-Counter Products That Work
Numbing gels and pastes containing benzocaine (sold as Anbesol, Orabase, Zilactin-B, and others) are the most widely available option. You apply a small amount directly to the sore, and it temporarily deadens the nerve endings in that spot. The relief is fast but wears off, so you may need to reapply several times a day, especially before meals.
Antiseptic rinses containing hydrogen peroxide (like Orajel Antiseptic Mouth Sore Rinse) serve double duty: they clean the ulcer and reduce the bacterial load around it, which can help prevent the sore from getting worse. These are particularly useful if you have more than one sore at a time and can’t easily dab each one individually.
Protective pastes that form a barrier over the sore are another option. They shield the raw tissue from contact with food, drinks, and your teeth, which is often what causes the sharpest bursts of pain throughout the day.
Prescription Treatments for Stubborn Sores
If over-the-counter products aren’t cutting it, a dentist or doctor can prescribe stronger options. Steroid ointments containing fluocinonide reduce inflammation directly at the sore, helping it shrink faster. For people dealing with multiple canker sores at once, a prescription mouth rinse containing a steroid or a numbing agent like lidocaine can treat the whole mouth at once rather than sore by sore.
In cases where a sore is especially large or painful, some providers use a chemical cauterizing agent applied directly to the ulcer. This essentially seals the nerve endings and can provide near-immediate pain relief, though the overall healing time remains about the same.
Preventing the Next One
Canker sores tend to come back, but a few changes can reduce how often they show up. One of the most practical is switching your toothpaste. Sodium lauryl sulfate (SLS), a foaming agent found in most major toothpaste brands, is a known soft tissue irritant. Many people who get frequent canker sores find they have fewer outbreaks after switching to an SLS-free toothpaste. Brands like Sensodyne, Biotene, and some versions of Tom’s of Maine skip this ingredient.
Nutritional gaps also play a role. Deficiencies in iron, folic acid, and vitamin B12 are all linked to recurrent mouth ulcers. If you’re getting canker sores frequently, especially alongside fatigue or a sore, reddened tongue, it’s worth having your levels checked. Correcting a deficiency through diet or supplements can make a noticeable difference in how often sores appear.
Stress and sleep deprivation are consistent triggers. You can’t always control your stress levels, but if you notice a pattern where sores pop up during high-pressure weeks, that connection is worth taking seriously. Physical trauma inside the mouth matters too: biting the inside of your cheek, aggressive brushing, or ill-fitting dental appliances can all kick off a new sore.
Canker Sores vs. Cold Sores
These two get confused constantly, but they’re completely different conditions with different causes and treatments. Canker sores appear inside the mouth, on the soft tissue of your cheeks, tongue, or the base of your gums. They look like a single round white or yellow ulcer with a red border. They are not contagious.
Cold sores (fever blisters) appear on the outside of the mouth, typically around the lips. They look like a cluster of small, fluid-filled blisters and are caused by herpes simplex virus type 1. They are contagious. If your sore is outside your mouth and looks blistery rather than like a single open ulcer, it’s likely a cold sore and needs antiviral treatment, not the remedies described here.
Signs a Canker Sore Needs Professional Attention
Most canker sores are a nuisance, not a medical emergency. But a sore that lasts longer than two weeks without improving, one that’s unusually large, or one accompanied by a fever deserves a professional look. The same goes for sores that keep coming back in clusters or that are so painful you can’t eat or drink enough to stay hydrated. In rare cases, a persistent mouth ulcer that won’t heal can signal something other than a simple canker sore, and a dentist or doctor can rule out other causes quickly with a visual exam or, if needed, a biopsy.