Most mouth blisters heal on their own within one to two weeks, but the right care can ease pain and speed that process along. The type of blister you’re dealing with determines the best approach, so identifying it is the first step toward relief.
Identify What You’re Dealing With
The two most common types of mouth blisters look and behave differently. Canker sores (aphthous ulcers) appear inside the mouth, usually on the inner cheeks, lips, or tongue. They’re typically a single round sore with a white or yellow center and a red border. They’re not contagious, and their exact cause isn’t fully understood, though injury, stress, smoking, and deficiencies in folic acid, iron, or vitamin B12 can all trigger them.
Cold sores (fever blisters) show up on the outside of the mouth, around the lips. They appear as clusters of small, fluid-filled blisters caused by the herpes simplex virus, usually type 1. Unlike canker sores, cold sores are contagious. The treatment strategies below focus primarily on canker sores and interior mouth blisters. Cold sores typically require antiviral treatment rather than the home remedies that work well for canker sores.
Saltwater and Baking Soda Rinses
A simple rinse is one of the most effective things you can do at home. St. Jude Children’s Research Hospital recommends this ratio: 1 teaspoon of table salt and 1 teaspoon of baking soda dissolved in 4 cups of warm water. Store the solution in a sealed container and use it several times a day, swishing gently for 30 seconds before spitting it out.
The salt draws fluid from swollen tissue, which reduces inflammation. The baking soda creates an alkaline environment that’s less hospitable to bacteria and helps neutralize acids in the mouth that irritate open sores. This combination won’t sting the way pure salt water sometimes can, and it’s safe to use as often as you need it.
Over-the-Counter Pain Relief
Topical gels and pastes containing a numbing agent (look for benzocaine on the label) can be applied directly to the sore to block pain for a few hours at a time. These are available at most pharmacies without a prescription. Some products also form a protective barrier over the sore, shielding it from further irritation while you eat or drink.
For more stubborn or painful sores, medicated mouthwashes combine several active ingredients: a numbing agent for pain, a coating agent (often an antacid base) to help the medicine stick to the lining of your mouth, and sometimes a corticosteroid to reduce swelling. These are typically used every four to six hours. After swishing, avoid eating or drinking for 30 minutes so the medicine has time to work. Prescription versions are available for severe or recurring cases.
Foods to Avoid While Healing
What you eat matters as much as what you apply to the sore. Three categories of food cause the most trouble:
- Spicy foods: Capsaicin directly irritates open sores. Skip hot sauce, salsa, chili powder, curry, and anything with hot peppers until you’ve healed.
- Acidic foods and drinks: Citrus fruits, tomatoes, pineapple, berries, vinegar, coffee, alcohol, and fruit juice can all cause a burning sensation and may delay healing.
- Hard or crunchy foods: Chips, pretzels, popcorn, granola, crackers, and crusty bread can scrape the sore and reopen it.
Stick to soft, cool, or room-temperature foods instead. Yogurt, smoothies (without citrus), mashed potatoes, scrambled eggs, and oatmeal are all gentle options. Hot food of any kind can make the pain worse, so let things cool down before eating.
Nutritional Gaps That Cause Recurring Sores
If you keep getting canker sores, your diet may be part of the problem. Low levels of vitamin B12, iron, folic acid, and ferritin (your body’s stored iron) are all linked to recurrent mouth ulcers. A clinical trial registered through the National Institutes of Health specifically investigated oral vitamin B12 as a treatment for people with frequent canker sores, reflecting how strong this nutritional connection is.
You don’t necessarily need supplements. Foods rich in B12 include meat, fish, eggs, and dairy. Leafy greens, beans, and fortified cereals supply folate. Red meat, lentils, and spinach are good iron sources. If your sores keep coming back despite good oral care, a blood test can check whether a deficiency is driving the cycle.
What the Healing Timeline Looks Like
Most mouth ulcers heal on their own without any treatment in about a week. With the rinses, topical treatments, and dietary adjustments described above, many people notice reduced pain within a day or two, though the sore itself still needs time to close. Minor canker sores (under 1 centimeter) rarely leave scars. Larger ones, sometimes called major aphthous ulcers, can take several weeks and occasionally scar.
The pain is usually worst in the first three to four days and gradually fades as the tissue regenerates. If you accidentally bite the area or eat something irritating, expect a temporary setback, but it won’t reset the healing clock entirely.
Signs That Need Medical Attention
A mouth sore that lasts longer than two weeks is no longer routine. Other reasons to see a doctor or dentist include: the sore appeared shortly after starting a new medication, you develop large white patches on the roof of your mouth or tongue, you have a fever or skin rash alongside the sore, you experience difficulty swallowing or excessive drooling, or you have a weakened immune system due to conditions like HIV or cancer treatment. Persistent or unusually large sores can occasionally signal an underlying condition that needs its own treatment rather than just symptom management.