Mouth ulcers on the gums develop when the soft tissue lining becomes damaged or inflamed, and the causes range from simple physical injury to underlying health conditions. Most gum ulcers are a type called aphthous ulcers (canker sores), which heal on their own within 10 to 14 days. But when they keep coming back or won’t go away, something deeper is usually driving them.
Physical Damage to the Gums
The most straightforward cause is mechanical trauma. Gum tissue is thin and easily irritated, so everyday things can break the surface and trigger an ulcer. Braces and orthodontic hardware are common culprits: brackets and wires rub against the gum line over time, wearing the tissue raw until a sore forms. Ill-fitting dentures do the same thing. Even aggressive toothbrushing with a hard-bristled brush, or accidentally jabbing yourself with a toothpick, can create enough damage for an ulcer to develop.
Dental procedures sometimes leave the gums vulnerable too. A cleaning that scrapes along the gum line or an injection site from local anesthesia can both produce small ulcers that appear a day or two later. These trauma-related ulcers are usually isolated, meaning you get one sore in one spot, and it heals without returning.
Chemical and Dietary Irritants
Certain toothpaste ingredients, particularly sodium lauryl sulfate (a foaming agent), are known to irritate gum tissue and contribute to ulcer formation. Switching to an SLS-free toothpaste is one of the simplest changes people make when ulcers keep recurring.
Acidic foods and drinks can also trigger or worsen gum ulcers. Coffee, soda, tomatoes, citrus fruits, and alcohol all lower the pH in your mouth, which irritates exposed tissue. If you already have a small ulcer forming, these can turn it into a larger, more painful one. Chocolate, peanuts, and eggs have also been identified as foods that worsen symptoms in people prone to recurring ulcers, though the mechanism isn’t fully understood and doesn’t appear to involve a true allergic reaction.
Nutritional Deficiencies
When mouth ulcers keep coming back without an obvious physical cause, a nutritional gap is one of the first things worth investigating. Iron deficiency is the most common finding: roughly 20% of people with recurrent aphthous ulcers are low in iron. About 5% are deficient in vitamin B12, and around 3% are low in folate. Anemia shows up in about 21% of recurrent ulcer patients overall.
The connection between B12 and mouth ulcers is well documented. In clinical reports, patients with recurring gum ulcers who were found to have low B12 levels saw their ulcers resolve once the deficiency was corrected. A daily sublingual B12 supplement taken over six months has been shown to reduce ulcer frequency regardless of whether a clear deficiency was present at the start. If your ulcers are frequent and you eat a diet low in red meat, leafy greens, or fortified foods, a simple blood test can check these levels.
Stress and Immune System Disruption
Stress is one of the most reliable triggers for gum ulcers. The classic example from medical literature: college students develop canker sores during final exams at noticeably higher rates. Stress affects immune function in ways that make the mucosal lining of the mouth more vulnerable to breakdown, though the exact pathway remains unclear.
People with compromised immune systems are especially prone to severe ulcers. Those with advanced HIV infection, for instance, often develop large canker sores that persist for weeks rather than the usual 10 to 14 days. Any condition or medication that suppresses immune function can increase both the frequency and severity of gum ulcers.
Viral and Bacterial Infections
Not all gum ulcers are canker sores. Herpes simplex virus type 1 (HSV-1), the same virus responsible for cold sores, is the most common infectious cause of gum ulcers. When HSV-1 affects the gums, it causes a condition called gingivostomatitis, which produces painful sores across the gums, tongue, and inner cheeks, often accompanied by fever, swollen lymph nodes, and bad breath.
The key difference between HSV-related gum sores and canker sores is that HSV sores are contagious (for about seven days after they appear) and tend to cluster in groups of small blisters. Canker sores are not contagious and usually appear as single, flat, round ulcers. HSV-related gum ulcers typically heal within two to three weeks, but the virus remains dormant in the body and can reactivate during periods of stress, fever, sun exposure, or physical trauma to the mouth.
Gut and Autoimmune Conditions
Recurring mouth ulcers can be an early or ongoing sign of a systemic inflammatory condition, particularly Crohn’s disease and celiac disease. Among people with inflammatory bowel disease (IBD), oral symptoms show up in anywhere from 5% to 50% of patients depending on the study, with Crohn’s disease producing mouth involvement more frequently than ulcerative colitis. One Italian survey found that over 65% of IBD patients reported oral symptoms during active flare-ups of their intestinal disease.
The ulcers can develop through several routes. Sometimes the mouth is simply another site where the same inflammatory process that damages the gut also attacks the oral lining. In other cases, the ulcers result from nutritional malabsorption: when the intestines can’t properly absorb iron, B12, or folate, deficiencies develop and the mouth pays the price. There’s a third possibility too. Some of the medications used to manage bowel disease alter the oral environment through immune suppression or direct tissue effects, leading to ulcers as a side effect of treatment rather than the disease itself.
If you’re experiencing recurrent gum ulcers alongside digestive symptoms like chronic diarrhea, bloating, or unexplained weight loss, it’s worth mentioning both sets of symptoms together to your doctor. Mouth ulcers sometimes appear before a formal IBD or celiac diagnosis.
When a Gum Ulcer Isn’t a Canker Sore
Most gum ulcers are harmless and heal within two weeks. But an ulcer that doesn’t heal in that timeframe needs professional evaluation, particularly if you use tobacco or drink alcohol regularly. The concern is oral cancer, which can initially look like a stubborn ulcer.
There are a few differences that matter. Canker sores are painful from the start and become less painful as they heal. Early oral cancers are usually painless. Canker sores are flat against the tissue, while cancerous lesions often have a small lump or bump underneath that you can feel with your tongue or finger. A spot that starts small and grows larger, a white patch that turns red, or a sore that begins bleeding when it previously didn’t are all signs worth getting checked. An ulcer that has lasted more than two weeks, or one that keeps recurring in the exact same spot, warrants a visit to your dentist or an oral medicine specialist.
Managing Recurrent Gum Ulcers
For occasional ulcers, the goal is pain relief while they heal on their own. Over-the-counter options include protective pastes that coat the ulcer and shield it from further irritation, and topical numbing gels that reduce pain during eating and drinking. Avoiding acidic foods and using a soft-bristled toothbrush during a flare-up helps prevent making the ulcer worse.
When ulcers are frequent or especially painful, prescription topical treatments can shorten healing time. These are typically anti-inflammatory pastes or rinses applied directly to the ulcer several times a day. For severe cases that don’t respond to topical treatment, stronger systemic options exist, but these come with more significant side effects and are reserved for people whose quality of life is substantially affected.
The most effective long-term strategy depends on identifying your specific trigger. If it’s a nutritional deficiency, correcting it often stops the cycle entirely. If it’s an oral hygiene product, switching brands can make a noticeable difference within weeks. If stress is the pattern, ulcers tend to follow predictable periods of high pressure, which at least makes them less alarming even if they’re hard to prevent completely.