The most effective things to put on a canker sore are topical numbing gels containing benzocaine or lidocaine, which provide immediate pain relief, and protective barrier products that shield the sore from food and friction. For faster healing, a simple saltwater or baking soda rinse works surprisingly well alongside these topical options. Most canker sores heal on their own within one to two weeks, but the right treatment can cut pain dramatically and speed things along.
Over-the-Counter Numbing Gels
Benzocaine gels are the go-to for immediate pain relief. Products like Orajel and Anbesol are applied directly to the sore up to four times a day, and they start numbing within seconds. The relief is temporary, usually lasting 20 to 30 minutes, but that window is enough to eat a meal or drink comfortably. Lidocaine-based products work the same way and are available in gel or liquid form.
These numbing agents don’t speed up healing. They simply block pain signals at the surface. If your main goal is to get through the day without wincing every time you chew, a numbing gel is your best first move.
Protective Barrier Products
Barrier products take a different approach: instead of numbing the sore, they cover it with a thin film that keeps food, drinks, and your teeth from irritating it. Some use a tissue adhesive that bonds to the moist surface of the ulcer. In one FDA-reviewed clinical trial, 76% of users reported reduced pain after a single application, and nearly half still had relief more than four hours later.
You can find these as patches, gels, or liquid sealants. Products like Canker Cover (a dissolving patch) and cyanoacrylate-based sealants physically sit over the sore, acting like a bandage inside your mouth. They work especially well for sores on the inner lip or cheek where friction from talking and eating is constant.
Saltwater and Baking Soda Rinses
A simple rinse is one of the oldest and most reliable treatments. Mix half a teaspoon of baking soda into 8 ounces of warm water and swish for 30 seconds, then spit. For a combined rinse, Cedars-Sinai recommends adding 1/8 teaspoon of salt and 1/4 teaspoon of baking soda to 8 ounces of warm water.
Baking soda neutralizes acids in the mouth that irritate the open sore, while salt draws out fluid and helps reduce swelling. Neither tastes great, but rinsing three to four times a day (especially after meals) keeps the area clean and creates a less hostile environment for healing. This is worth doing even if you’re also using a topical product.
Hydrogen Peroxide
Dabbing a canker sore with diluted hydrogen peroxide is another common home treatment. Mix equal parts 3% hydrogen peroxide and water, then apply it to the sore with a cotton swab. The fizzing action helps clean debris from the ulcer’s surface. You can also swish a small amount of the diluted solution around your mouth as a rinse. Avoid swallowing it, and don’t use it more than a few times a day since it can irritate healthy tissue with overuse.
Prescription Steroid Paste
When a canker sore is large, unusually painful, or keeps coming back, a prescription-strength steroid paste can make a real difference. These pastes reduce inflammation directly at the sore, which both eases pain and helps it heal faster. You press a small dab (about a quarter inch) onto the sore until a thin film forms. Don’t rub it in, or the paste crumbles into a gritty mess.
The best time to apply is at bedtime so the medication stays in contact with the sore overnight. For severe cases, you may need to apply it two or three times a day, ideally after meals when the area is relatively clean and dry. This requires a prescription from a doctor or dentist, so it’s typically reserved for sores that aren’t responding to over-the-counter options.
Chemical Cauterization at the Dentist
If you want faster results and don’t mind a brief dental visit, your dentist can chemically cauterize the sore. A product called Debacterol uses a chemical agent to seal the ulcer surface, potentially reducing healing time to about a week even for serious sores. Silver nitrate is another option. It doesn’t necessarily speed healing, but it typically eliminates the pain. Both involve applying a chemical directly to the sore for a few seconds. There’s a brief sting, followed by significant relief.
Low-level laser treatment is another in-office option gaining traction. A 30-second exposure to red laser light in the 650 to 680 nanometer range has been shown to increase healing rates for a variety of oral ulcers. Larger sores (bigger than 3 millimeters) may need a second pass to cover the full area. Not every dental office offers this, but it’s worth asking about if you deal with frequent canker sores.
Vitamin B12 for Prevention
If canker sores are a recurring problem for you, what you put in your body may matter as much as what you put on the sore. A clinical trial of 58 patients with recurring canker sores found that taking 1,000 micrograms of vitamin B12 at bedtime led to complete remission in 74% of participants after six months. Only 32% of the placebo group saw the same result. That’s a striking difference for a cheap, widely available supplement.
B12 deficiency is one of several nutritional gaps linked to recurrent canker sores. Iron, folate, and zinc deficiencies are also associated with frequent outbreaks. If you get canker sores more than a few times a year, it’s worth checking whether a nutritional gap could be contributing.
Switch to SLS-Free Toothpaste
Sodium lauryl sulfate, the foaming agent in most toothpastes, is a known irritant to oral tissue. Research has shown that SLS-containing toothpaste can increase the frequency of recurring canker sores, and one clinical study found four times fewer soft tissue lesions in people using SLS-free toothpaste compared to a standard formula. Brands like Sensodyne, Biotene, and Verve are SLS-free and widely available. This single switch is one of the easiest things you can do if canker sores are a regular problem for you.
When a Canker Sore Needs Attention
Most canker sores are minor and heal within two weeks without any treatment at all. But a sore that lasts longer than two weeks, measures larger than a centimeter (roughly the size of a pea), or comes with a fever warrants a visit to your doctor or dentist. Persistent or unusually large sores occasionally signal something other than a routine canker sore, and a professional can rule out other causes or prescribe stronger treatment to help it resolve.