Mouth ulcers are small, painful sores that form on the soft tissues inside your mouth, including the inner cheeks, lips, gums, tongue, and the floor of the mouth. They affect anywhere from 5% to 66% of the population depending on the study, making them one of the most common oral complaints. Most are harmless and heal on their own within one to two weeks, but they can make eating, drinking, and talking genuinely miserable in the meantime.
Types of Mouth Ulcers
The most common type is the aphthous ulcer, often called a canker sore. These are not contagious and have nothing to do with the herpes virus, despite looking similar. Aphthous ulcers come in three forms:
- Minor aphthous ulcers are the most frequent. They’re small (under 1 cm across), shallow, and typically appear on the inner cheeks, lips, soft palate, or floor of the mouth. You might get one at a time or a few at once. These generally heal without scarring.
- Major aphthous ulcers are larger and penetrate deeper into the tissue. They take longer to resolve and can leave scars behind.
- Herpetiform ulcers show up as clusters of many tiny sores that can merge together. Despite the name, they aren’t caused by the herpes virus.
Other types of mouth sores include cold sores (which are caused by the herpes simplex virus and appear on or around the lips), traumatic ulcers from an injury, and sores linked to underlying medical conditions.
What Causes Them
The exact mechanism behind aphthous ulcers isn’t fully understood, but the triggers are well documented. The most common is simple mechanical trauma: biting the inside of your cheek, scraping your gums with a toothbrush, irritation from braces or dentures, or burning your mouth on hot food. In survey-based research, trauma from biting and friction consistently ranks as the top local trigger.
Stress is another major factor. Psychological stress appears to alter immune function in ways that make the mouth lining more vulnerable to breaking down. Many people notice ulcers flaring during high-pressure periods at work or school.
Diet plays a role too. Acidic foods like citrus fruits, tomatoes, and pineapple can irritate the mouth lining or trigger ulcers in people who are sensitive. Some people also react to spicy foods, chocolate, coffee, or specific food allergens.
Nutritional Deficiencies
Recurring mouth ulcers can signal that your body is low on certain nutrients. A study comparing people with recurrent ulcers to healthy controls found that about half of the ulcer patients were deficient in vitamin B12, compared to none in the control group. Folate deficiency was also common, present in roughly 46% of patients. Iron deficiency, measured through ferritin levels, played a smaller but still notable role. If your ulcers keep coming back without an obvious trigger, a blood test checking these levels is a reasonable step.
Medical Conditions
Frequent or severe mouth ulcers sometimes point to a systemic condition. Celiac disease is one of the better-known links. People with celiac disease experience more frequent and more severe canker sore outbreaks, and for some, recurring mouth ulcers are the first noticeable sign of the disease. Inflammatory bowel conditions like Crohn’s disease, Behçet’s syndrome (an autoimmune condition that causes inflammation in blood vessels), and certain immune deficiencies can also produce chronic oral ulcers. Hormonal shifts, particularly around menstruation, are another recognized trigger.
How to Treat Mouth Ulcers at Home
Most minor ulcers don’t need medical treatment. A saltwater rinse is the simplest option. Dissolve half a teaspoon of salt in a cup of warm water and swish it around your mouth for 30 seconds. It stings, but it helps dry out the sore and keep the area clean. Repeating this a few times a day can speed things along.
Honey has some evidence behind it as well. Research suggests it reduces pain, redness, and the overall size of canker sores while also helping prevent secondary infection. Dabbing a small amount of raw honey directly on the ulcer a few times a day is a low-risk approach worth trying.
Over-the-counter numbing gels containing ingredients like benzocaine or lidocaine can temporarily block pain, especially before meals. Protective oral gels work differently. They coat the ulcer and form a barrier over exposed nerve endings, reducing pain through physical shielding rather than medication. Both types are available at most pharmacies.
For ulcers that are particularly large, painful, or slow to heal, a doctor or dentist may prescribe a topical steroid paste. These reduce inflammation directly at the site and can shorten healing time significantly. They’re applied as a thin film over the sore, usually after meals and before bed.
Preventing Recurrences
If you get mouth ulcers frequently, prevention matters more than treatment. Start with the basics: use a soft-bristled toothbrush, eat slowly to avoid biting your cheeks, and limit acidic or spicy foods that seem to trigger your outbreaks.
You may have heard that switching to a toothpaste free of sodium lauryl sulfate (SLS), the foaming agent in most toothpastes, can help. The evidence on this is mixed. SLS can irritate the mouth lining, and some research has found that avoiding it reduces ulcer frequency. But a 2019 review concluded there wasn’t enough data to confirm that SLS-free toothpaste meaningfully reduces how often ulcers occur, how long they last, or how much they hurt. It’s a low-cost experiment if you want to try it, but don’t expect dramatic results.
Addressing nutritional gaps is more likely to make a real difference. Ensuring adequate intake of vitamin B12, folate, and iron through diet or supplements can reduce recurrences for people whose levels are low. Foods rich in B12 include meat, fish, eggs, and dairy. Folate comes from leafy greens, legumes, and fortified grains. Iron sources include red meat, beans, and spinach.
When a Mouth Ulcer Could Be Something Else
The key distinction most people searching this topic need to understand is the difference between a typical canker sore and something more serious. A standard aphthous ulcer hurts, but it heals. The red flag is an ulcer that doesn’t heal.
Mouth cancer can initially look like an ordinary sore. The warning signs include a mouth ulcer that persists beyond two to three weeks, a lump in the mouth or neck, white or red patches on the inside of the mouth, unexplained bleeding or numbness, pain when swallowing, or changes to your speech. Any ulcer that hasn’t started improving after two weeks deserves a professional look. This is especially true if you smoke, drink alcohol heavily, or are over 50, as these are the strongest risk factors for oral cancer.