Most canker sores heal on their own within 10 to 14 days, but the right home care can cut down pain and speed that timeline. These small, round ulcers form inside the mouth on soft tissue like the inner cheeks, gums, or tongue, and while they’re not dangerous, they can make eating and talking miserable.
Saltwater and Baking Soda Rinses
The simplest and most effective first step is a saltwater rinse. Mix 1 teaspoon of salt into 1 cup of warm water, swish it around your mouth for about 30 seconds, and spit it out. Do this several times a day, especially after meals. Salt draws fluid out of the sore, which helps reduce swelling and creates an environment that’s harder for bacteria to thrive in. It will sting for a few seconds, but the relief afterward is noticeable.
Baking soda works similarly. Dissolve 1 teaspoon in half a cup of warm water and rinse the same way. Baking soda neutralizes acids in your mouth that irritate the open sore, which is especially helpful if acidic foods triggered the ulcer in the first place.
Protective Coatings That Reduce Pain
One of the reasons canker sores hurt so much is that they’re exposed wounds constantly being touched by your tongue, teeth, and food. Coating the sore with a protective layer helps block that contact. Milk of magnesia works well for this. Dab a small amount directly onto the sore three to four times a day. It forms a temporary barrier and also neutralizes acid around the ulcer.
For more intense pain, you can combine milk of magnesia with liquid diphenhydramine (the antihistamine found in liquid allergy medicine). Mix equal parts, swish the mixture in your mouth for about a minute, and spit it out. The antihistamine has a mild numbing effect on the tissue, and the milk of magnesia coats the sore. Don’t swallow the mixture.
Over-the-counter oral gels containing benzocaine also numb the area on contact. Apply them directly to the sore before meals to make eating less painful. These don’t speed healing, but they make the waiting period much more tolerable.
What Triggers Canker Sores
Canker sores often come back because the underlying trigger hasn’t been addressed. The most common culprits are mechanical injury (biting your cheek, aggressive brushing, or irritation from braces), acidic or spicy foods, stress, and hormonal shifts. Switching to a soft-bristled toothbrush and a toothpaste free of sodium lauryl sulfate, a foaming agent that irritates mouth tissue, can reduce recurrences significantly.
Nutritional gaps also play a role. Deficiencies in iron, vitamin B12, folic acid, and zinc are all linked to recurrent canker sores. If you get them frequently, it’s worth looking at whether your diet provides enough of these nutrients. Leafy greens, beans, fortified cereals, and lean meats cover most of them. A basic blood panel can identify a deficiency if dietary changes alone don’t help.
When a Canker Sore Needs Prescription Treatment
Most canker sores are minor, meaning they’re small, shallow, and gone within two weeks without scarring. Major canker sores are a different situation. They’re deeper, often larger than a centimeter (roughly the size of a pea), and can last weeks to months, sometimes healing with scar tissue.
If home remedies aren’t controlling the pain or the sore isn’t healing, a doctor or dentist can prescribe a steroid dental paste. This is a thick paste you press onto the sore in a small dab, about a quarter inch, until a thin film forms over the ulcer. You don’t rub it in. Applied at bedtime, it keeps the steroid in contact with the sore overnight, reducing inflammation and speeding healing. For severe outbreaks, it can be applied two to three times a day after meals.
Canker Sores vs. Cold Sores
These two get confused constantly, but they’re completely different conditions that require different treatment. The easiest way to tell them apart is location. Canker sores form inside the mouth. Cold sores form outside the mouth, typically around the border of the lips. They also look different: a canker sore is a single round white or yellow ulcer with a red border, while a cold sore is 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 other people.
Signs a Sore Needs Medical Attention
A canker sore that lasts longer than two weeks, is larger than a centimeter, comes with a high fever, or keeps returning in clusters warrants a visit to your doctor or dentist. Persistent mouth ulcers can occasionally signal other conditions, including autoimmune disorders or, rarely, oral cancer. A single stubborn sore that doesn’t follow the normal healing timeline is worth getting checked, especially if it’s painless, since canker sores are almost always painful.