Most canker sores inside the lip heal on their own within 10 to 14 days, but the right home treatments can cut pain significantly and may speed that timeline. These small, round ulcers with a white or yellow center and red border form on the soft tissue inside your mouth, and unlike cold sores, they aren’t contagious or caused by a virus. While you wait for healing, several remedies can make eating and talking far less miserable.
Salt Water and Baking Soda Rinses
The simplest and most effective first step is rinsing your mouth with salt water or baking soda several times a day. For a baking soda rinse, dissolve 1 teaspoon of baking soda in half a cup of warm water. For a salt water rinse, use roughly the same ratio. Swish gently for 30 seconds, then spit. Doing this after meals and before bed keeps the area clean and reduces the bacterial load around the ulcer, which helps your tissue repair itself faster.
Over-the-Counter Pain Relief
Topical gels and pastes containing numbing agents (look for benzocaine on the label) can dull the sting for an hour or two at a time. Apply a small amount directly to the sore with a clean fingertip or cotton swab. These products work best when you dry the area gently with a tissue first so the gel actually sticks to the ulcer instead of washing away with saliva.
Protective oral pastes create a barrier film over the sore, shielding it from friction and acidic foods. You press a small dab onto the ulcer and let a thin coating develop without rubbing it in. Applying one of these at bedtime is especially useful because it keeps the sore covered through the night when your mouth produces less saliva.
Chemical Cauterization for Fast Pain Relief
If you want near-instant pain relief, a product called Debacterol is available by prescription. It contains tissue-denaturing compounds that essentially seal the exposed nerve endings on the ulcer’s surface. Your dentist or doctor applies it with a swab for no more than 10 seconds. You’ll feel a sharp sting during application, but after rinsing with water, the ulcer pain subsides almost immediately. This is one of the fastest ways to eliminate canker sore pain, though it doesn’t prevent new sores from forming.
Prescription Options for Severe Sores
For larger or more painful sores, a dentist may prescribe a steroid dental paste. You dab about a quarter inch of paste onto the sore to form a thin film, ideally at bedtime and after meals, two to three times daily. The steroid reduces inflammation by dialing down your body’s chemical pain and swelling signals at the site. Most people see noticeable improvement within a week. If the sore hasn’t started healing after seven days of use, that’s a sign to follow up with your provider.
What Triggers Canker Sores
Canker sores don’t have a single known cause, which makes them frustrating. But several triggers are well established: physical injury to the tissue (biting your cheek, a sharp chip, aggressive brushing), emotional stress, and nutritional deficiencies in iron, folate, or vitamin B12. If you get canker sores repeatedly, it’s worth asking your doctor to check your levels. Low folate (below 280 ng/ml), low B12 (below 220 pg/ml), or low iron stores can all make you more prone to recurrent ulcers, and correcting the deficiency often reduces how frequently they appear.
Your toothpaste may also play a role. Many common toothpastes contain sodium lauryl sulfate (SLS), a foaming agent that can irritate soft oral tissue. Research has shown that SLS toothpaste increases the frequency of repeated mouth ulcers in susceptible people. Switching to an SLS-free toothpaste is a low-cost experiment worth trying if you deal with canker sores regularly.
How to Avoid Making It Worse
While the sore is healing, steer clear of acidic foods like citrus, tomatoes, and vinegar-based dressings. Spicy foods and anything with rough or sharp edges (tortilla chips, crusty bread) will irritate the ulcer and reset the pain cycle. Using a soft-bristled toothbrush and being careful around the sore while brushing prevents reinjury to tissue that’s trying to repair itself.
Types of Canker Sores and Healing Times
Most canker sores are the minor type: under a centimeter across, shallow, and gone within 10 to 14 days without scarring. These are the ones you’ll typically find inside your lip.
Major canker sores are a different experience. They can grow to 1 to 3 centimeters in diameter, take up to six weeks to heal, and often leave scars. A third type, called herpetiform ulcers, appears as clusters of tiny pinpoint sores that can merge into larger irregular shapes. Despite the name, these aren’t caused by herpes.
Signs a Sore Needs Medical Attention
A typical canker sore, while painful, resolves on its own within one to three weeks. But certain features warrant a closer look. If a sore persists beyond three weeks, grows unusually large (over a centimeter), or feels hard or fixed to the tissue underneath when you press on it, those are signs that something more serious could be going on. Hardening at the base of an ulcer or attachment to deeper tissue can indicate oral cancer, and a biopsy is the standard next step to rule that out. Frequent recurrences, sores that come in clusters, sores accompanied by fever, or difficulty swallowing also deserve professional evaluation.
Canker Sores vs. Cold Sores
These two get confused constantly, but they’re completely different conditions. Canker sores appear inside the mouth, on the inner cheeks, lips, or tongue. They look like a single round ulcer with a white or yellow center. Cold sores (fever blisters) show up on the outside of the mouth, around the lips, as a cluster of small fluid-filled blisters. Cold sores are caused by herpes simplex virus type 1 and are contagious. Canker sores are not caused by any virus and cannot be passed to another person.