Most canker sores heal on their own within one to two weeks, but you can speed up recovery and cut the pain significantly with a few simple steps. The key is reducing irritation, numbing the area, and keeping the sore clean so it doesn’t get worse.
Start With a Salt Water or Baking Soda Rinse
A warm rinse is the simplest and cheapest first move. Mix 2 cups of warm water with half a teaspoon of baking soda and a quarter teaspoon of salt, then swish it around your mouth for 30 seconds and spit. Follow with a rinse of plain water. You can repeat this several times a day, especially after meals when food particles are most likely to irritate the sore.
The rinse works by gently cleaning the ulcer and creating a slightly alkaline environment that discourages bacterial growth. It won’t sting as much as you’d expect, and most people notice the area feels calmer afterward.
OTC Pain Relief That Actually Works
For direct pain relief, look for an over-the-counter gel or paste containing benzocaine (sold under names like Orajel and Anbesol). These topical numbing agents coat the sore and temporarily block pain signals from the exposed nerve endings. Apply a small amount directly to the ulcer with a clean finger or cotton swab. The effect kicks in within a minute or two and typically lasts 30 to 60 minutes.
Another option from the Cleveland Clinic: dab a cotton swab soaked in a 50/50 mix of water and hydrogen peroxide onto the sore, then follow with a small dab of milk of magnesia. You can do this up to four times a day. Just be careful not to swallow the hydrogen peroxide.
If you use a mouthwash, choose one that’s alcohol-free. Alcohol-based rinses will burn on contact and can dry out the tissue around the ulcer, slowing healing.
Avoid What Makes It Worse
What you stop doing matters as much as what you start doing. Spicy, acidic, and crunchy foods are the biggest irritants. Citrus fruits, tomato sauce, chips, and anything with vinegar can re-traumatize the ulcer every time you eat. Stick to softer, blander foods until the sore closes up.
Your toothpaste may also be a factor. Many common toothpastes contain sodium lauryl sulfate (SLS), a foaming agent that strips the protective mucus layer inside your mouth and leaves the tissue underneath more vulnerable. A systematic review in the Journal of Oral Pathology and Medicine found that people who switched to SLS-free toothpaste had significantly fewer ulcers, shorter episodes, and less pain. If you get canker sores regularly, switching toothpaste is one of the easiest changes you can make. Brands like Sensodyne and some versions of Tom’s of Maine are SLS-free.
Check for Nutritional Gaps
Recurring canker sores, meaning several per year or new ones appearing before old ones heal, sometimes signal a nutritional deficiency. In a study of 273 people with recurrent canker sores, roughly 20% were deficient in iron, about 5% were low in vitamin B12, and nearly 3% had low folate levels. Anemia was present in about 21% of that group.
You don’t need to start supplementing blindly, but if your sores keep coming back, it’s worth paying attention to whether your diet is low in red meat, leafy greens, eggs, or fortified cereals. These are the primary dietary sources of iron, B12, and folate. A simple blood test can confirm whether a deficiency is contributing.
When a Canker Sore Needs Medical Attention
A typical canker sore is a single round white or yellow ulcer with a red border, located inside the mouth on the cheeks, gums, tongue, or soft palate. It hurts, but it heals. The threshold for concern is three weeks. Any mouth ulcer that hasn’t healed after three weeks should be evaluated by a doctor or dentist, because persistent ulcers can occasionally indicate something more serious, including oral cancer.
Other reasons to seek care: sores that are unusually large (roughly the size of a pencil eraser or bigger), sores that come in clusters of many at once, sores accompanied by high fever, or pain so severe that you can’t eat or drink enough to stay hydrated. For these cases, a doctor can prescribe a steroid rinse or paste that reduces inflammation and accelerates healing far beyond what OTC products can do.
Canker Sore or Cold Sore?
These get confused constantly, but they’re completely different conditions. Canker sores appear inside the mouth and look like a single round white or yellow crater with a red ring. Cold sores (fever blisters) appear outside the mouth, typically along the border of the lips, and look like a cluster of small fluid-filled blisters. Cold sores are caused by the herpes simplex virus and are contagious. Canker sores are not viral and cannot spread to another person.
This distinction matters because the treatments are different. Antiviral creams for cold sores won’t help a canker sore, and the rinses and numbing gels described above aren’t designed for cold sores. If your sore is outside the mouth and blister-like, you’re dealing with a cold sore and need a different approach.