Most canker sores heal on their own within one to two weeks, but you can speed up relief and reduce pain starting today with a few simple steps. These small, round ulcers inside your mouth are not dangerous and not contagious, but they can make eating and talking miserable while they last.
Rinses That Reduce Pain and Speed Healing
The simplest and cheapest thing you can do right now is rinse your mouth with a salt water or baking soda solution. Dissolve 1 teaspoon of baking soda in half a cup of warm water, swish it around for 30 seconds, and spit. You can do this several times a day, especially after meals. A similar rinse with half a teaspoon of table salt in warm water works too. These rinses help neutralize acids in your mouth that irritate the sore and create a cleaner environment for healing.
Over-the-Counter Pain Relief
If rinsing alone isn’t enough, topical numbing gels or pastes containing 20% benzocaine are widely available at pharmacies. You apply a small amount directly to the sore, and it temporarily numbs the area so you can eat or drink without wincing. Reapply as needed, but don’t overdo it. Numbing agents can cause rare but serious side effects if used excessively, so follow the directions on the package and use the smallest amount that helps.
You can also find protective pastes that form a barrier over the sore, shielding it from food and saliva. Hydrogen peroxide rinses (diluted to half strength with water) are another option that helps keep the area clean. Over-the-counter anti-inflammatory pain relievers like ibuprofen can take the edge off if the sore is making your whole mouth ache.
What to Eat and What to Avoid
Certain foods will make a canker sore significantly worse. Acidic foods like citrus fruits, tomatoes, and vinegar-based dressings sting on contact. Spicy foods, salty snacks, and anything with rough or sharp edges (think chips, crackers, crusty bread) can scrape the ulcer and restart the pain cycle. Coffee and other caffeinated drinks may also irritate the area.
Stick to soft, bland, cool foods while you’re healing. Yogurt, smoothies, oatmeal, scrambled eggs, and mashed potatoes are all easy choices. Drinking through a straw can help liquids bypass the sore if it’s on your inner lip or cheek.
What Triggers Canker Sores
Canker sores can seem random, but they often have identifiable triggers. Common ones include stress, minor mouth injuries (biting your cheek, aggressive brushing, dental work), hormonal changes, and certain foods. Some people notice flare-ups after eating specific items like cheese, nuts, eggs, or acidic fruits, even when those foods don’t cause problems for others.
Nutritional deficiencies play a role too. Low levels of iron, zinc, folate, or vitamin B12 have all been linked to recurring canker sores. If you get them frequently, it’s worth looking at your diet or asking about blood work to check for deficiencies. Conditions that affect the immune system or the gut, like celiac disease, can also cause repeated outbreaks.
Switching to a toothpaste without sodium lauryl sulfate (a foaming agent) has helped some people reduce how often sores appear. It’s a low-risk change worth trying if you deal with canker sores regularly.
When a Canker Sore Needs Medical Attention
Most canker sores are minor, under a centimeter across, and resolve within 7 to 14 days without scarring. Larger sores, called major aphthous ulcers, can exceed a centimeter, take weeks or even months to heal, and sometimes leave scars. If your sore hasn’t improved after two weeks, is unusually large, comes with a fever, or keeps coming back in clusters, it’s worth getting evaluated.
For persistent or severe cases, prescription options exist. Steroid-based mouth rinses or pastes reduce inflammation directly at the sore. These are stronger than anything available over the counter and can shorten healing time noticeably. In rare, very stubborn cases, oral medications that calm the immune response may be considered.
Canker Sores vs. Cold Sores
People often confuse these two, but they’re completely different. Canker sores appear inside the mouth, on the inner cheeks, lips, tongue, or soft palate. They look like single round white or yellow sores with a red border. They are not caused by a virus and cannot be spread to another person.
Cold sores (fever blisters) appear outside the mouth, typically around the border of the lips. They show up as clusters of small fluid-filled blisters and are caused by the herpes simplex virus. If your sore is on the outside of your lip and looks blistered, it’s likely a cold sore and requires a different treatment approach.