The best things to put on a canker sore are over-the-counter numbing gels, protective oral pastes, or a simple baking soda rinse. Most canker sores heal on their own within one to two weeks, but topical treatments can cut down pain significantly and may speed up the process. What you choose depends on whether you want immediate pain relief, a protective barrier, or both.
Numbing Gels and Oral Pain Relievers
Over-the-counter oral gels containing benzocaine are the most widely available option for canker sore pain. You apply a small amount directly to the sore, and it numbs the area within a minute or two. The relief typically lasts 30 to 60 minutes, which makes eating and drinking much more comfortable. Look for products labeled specifically for mouth sores rather than general topical pain relievers, since these are formulated to stick to wet tissue.
Antiseptic rinses containing hydrogen peroxide are another common OTC choice. These work differently: rather than numbing pain, they clean the sore and reduce bacteria that can slow healing. You can find pre-mixed rinses designed for mouth sores, or dilute standard 3% hydrogen peroxide with equal parts water and dab it on with a cotton swab. The tradeoff is a stinging sensation on contact, which fades quickly.
Baking Soda and Salt Water Rinses
If you want something you can make right now from kitchen ingredients, a baking soda rinse is a solid option. Dissolve one teaspoon of baking soda in half a cup of warm water, swish it around your mouth for 30 seconds, and spit. Baking soda neutralizes acids in your mouth that irritate the open sore, creating a less hostile environment for healing. You can repeat this several times a day, especially after meals.
A plain salt water rinse works similarly. Use about half a teaspoon of salt in a cup of warm water. Salt draws fluid out of the inflamed tissue, which temporarily reduces swelling. It stings on contact, but many people find the relief afterward worth it. Neither rinse will dramatically shorten healing time, but both reduce discomfort and help keep the area clean.
Protective Barriers and Pastes
One of the most frustrating things about canker sores is that every bite of food, sip of coffee, or brush of your tongue reopens the irritation cycle. Protective pastes and patches address this by forming a physical barrier over the sore. Over-the-counter oral adhesive pastes create a thin film that shields the ulcer from contact with food, teeth, and saliva. Apply a small dab to a dry sore and press gently; the paste sticks to the moist tissue and stays in place for a few hours.
The challenge with any oral barrier is that it gets washed away. Saliva, eating, and drinking all gradually dissolve these products, so you’ll need to reapply throughout the day. Researchers at Texas A&M have been developing bioadhesive patches designed to stay in place longer and deliver medication directly to the sore, but current OTC options still require frequent reapplication. For best results, apply protective pastes after meals rather than before, so you get the longest window of coverage.
Prescription Options for Severe Sores
When a canker sore is unusually large (bigger than a centimeter), lasts longer than two weeks, or keeps coming back, a dentist or doctor can prescribe stronger treatments. Prescription-strength corticosteroid mouth rinses reduce the inflammatory response driving the pain and swelling. Steroid pastes applied directly to the sore work the same way but in a more concentrated form. These treatments can meaningfully shorten healing time for major canker sores that wouldn’t resolve quickly on their own.
For people who get frequent outbreaks, prescription options may also include oral medications that address the underlying immune response rather than treating each sore individually. This is a conversation worth having with your doctor if you’re getting canker sores more than a few times a year.
Foods and Substances to Keep Away
What you avoid putting on a canker sore matters almost as much as what you apply. Acidic foods are the biggest offenders: citrus fruits, tomatoes, tomato-based sauces, and vinegar-heavy dressings all irritate the exposed tissue and intensify pain. Salty or crunchy foods like chips, pretzels, and raw nuts can physically scrape the sore, restarting inflammation. Spicy foods have the same effect through chemical irritation.
While your sore is healing, stick to soft, bland, cool foods. Yogurt, smoothies, oatmeal, scrambled eggs, and mashed potatoes are all safe choices. Drinking through a straw can help liquids bypass a sore on your lip or the front of your mouth. Avoid very hot beverages, which increase blood flow to the area and can make swelling worse.
Switching Toothpaste Can Prevent New Sores
If you get canker sores repeatedly, your toothpaste may be part of the problem. A systematic review published in the Journal of Oral Pathology and Medicine found that people who switched to toothpaste free of sodium lauryl sulfate (SLS), a common foaming agent, developed significantly fewer canker sores. Across the studies analyzed, SLS-free toothpaste users averaged about one fewer ulcer per outbreak period, nearly two fewer days of ulcer duration per episode, and reported meaningfully less pain.
SLS is a detergent that strips away the protective mucous layer inside your mouth, leaving tissue more vulnerable to small injuries that can trigger canker sores. Most major toothpaste brands use it, but SLS-free alternatives are easy to find in drugstores or online. If you’re prone to recurrent sores, this is one of the simplest changes you can make. People with gluten sensitivity or celiac disease should also be aware that gluten consumption can trigger canker sores, so managing dietary triggers may help reduce outbreaks.
A Simple Treatment Routine
For a typical canker sore, a practical approach combines two or three of these strategies. Rinse with baking soda or salt water after meals to clean the area. Apply a numbing gel before eating if pain makes chewing difficult. Use a protective paste between meals to shield the sore from further irritation. Avoid acidic, salty, and crunchy foods until healing is well underway.
Most canker sores peak in pain around days three to four and then gradually shrink over the following week. If a sore hasn’t started improving after 10 days, is unusually large, comes with fever, or makes it genuinely difficult to eat or drink, it’s worth getting it looked at. Major canker sores, those over a centimeter across, can take up to six weeks to heal and sometimes benefit from prescription treatment to speed things along.