Tongue ulcers are most often caused by minor physical trauma, like biting your tongue while chewing, but they can also result from nutritional deficiencies, viral infections, immune system reactions, certain medications, and occasionally systemic diseases. Most tongue ulcers heal on their own within 10 to 14 days. When they don’t, the cause is usually something worth investigating.
Canker Sores: The Most Common Culprit
The majority of tongue ulcers are canker sores, known clinically as recurrent aphthous stomatitis. These are small, shallow sores with a white or yellowish center and a red border. They tend to appear on the softer, non-keratinized surfaces of the mouth, including the sides and underside of the tongue.
The underlying mechanism involves an overactive immune response. Your body’s T-cells release inflammatory signals that recruit other immune cells to the area, causing localized swelling and eventually destroying a small patch of the surface tissue. What triggers this reaction varies from person to person, but genetics play a strong role: up to 46% of people with recurrent canker sores have a family history of them.
Common triggers include:
- Stress, both emotional and physical
- Local trauma from biting, sharp foods, or dental work
- Hormonal shifts, particularly during menstruation and menopause (pregnancy and oral contraceptives tend to reduce outbreaks)
- Nutritional deficiencies, especially iron, folate, vitamin B12, and zinc
- Smoking cessation, which paradoxically increases risk because nicotine promotes a thicker, more protective layer on the oral lining
Minor canker sores typically heal within two weeks without scarring. Major canker sores, which are larger and deeper, can last anywhere from 10 days to six weeks or longer and may leave scars.
Physical Injury and Irritation
Accidentally biting your tongue during chewing is one of the most straightforward causes of a tongue ulcer. This also happens during seizures or from a blow to the jaw when the tongue is between the teeth. Sharp or broken fillings, chipped teeth, and poorly fitted dental appliances can repeatedly scrape the same spot on the tongue, creating a chronic ulcer that won’t heal until the source of irritation is removed.
Acute traumatic ulcers usually become painless within three days of the injury and heal within 10 days. Chronic traumatic ulcers, where the irritation continues, can persist for weeks. If you notice a sore that lines up with a rough tooth edge or a new dental appliance, that’s likely the cause.
Nutritional Deficiencies
Low levels of vitamin B12, iron, and folate are well-established triggers for tongue ulcers and tongue inflammation. In one study of patients with tongue problems, 68% were deficient in vitamin B12 and about 14% were deficient in iron stores. Normal vitamin B12 levels fall between 180 and 914 ng/L, so values well below 180 are a clear red flag. Folate deficiency (below 4.0 ng/mL) and low iron stores can also contribute.
These deficiencies impair your body’s ability to maintain healthy oral tissue and can make existing ulcers slower to heal. If you’re getting recurrent tongue ulcers without an obvious cause, a simple blood test can check for these. Vegetarians, vegans, people with digestive conditions that impair absorption, and heavy alcohol users are at higher risk for B12 and folate shortfalls.
Viral Infections
The herpes simplex virus is a common cause of tongue ulcers, particularly during an initial infection. The first outbreak, called herpetic stomatitis, often appears in childhood and can cause blisters on the tongue, cheeks, roof of the mouth, and gums. These blisters rupture and form painful ulcers, sometimes accompanied by a fever as high as 104°F. The sores typically heal within 5 to 10 days.
After the first infection, the virus stays dormant in the body. Reactivations usually cause cold sores on the lips rather than inside the mouth, though they can occasionally affect the tongue again in a milder form. The shingles virus can also produce oral ulcers, which tend to heal within 10 to 14 days.
Your Toothpaste Might Be Making It Worse
A foaming agent called sodium lauryl sulfate (SLS), found in most toothpastes, has been shown to irritate the oral lining and worsen canker sores. Multiple clinical trials have found that people who switched to SLS-free toothpaste experienced fewer ulcers, shorter healing times, and less pain. In one trial of 90 patients, the healing duration and pain scores were significantly lower in the SLS-free group. Case reports have also documented inflammatory reactions specifically on the top surface of the tongue from SLS-containing products.
If you get frequent tongue ulcers, switching to an SLS-free toothpaste is a low-risk change worth trying. Several brands market themselves as SLS-free, and the ingredient list on the back of any tube will tell you.
Medications That Cause Oral Ulcers
Several classes of medication can cause or worsen tongue ulcers as a side effect. The drugs most directly linked to recurrent oral ulceration include chemotherapy agents (particularly methotrexate), the heart medication nicorandil, and propylthiouracil (used for thyroid conditions). NSAIDs like naproxen and the antibiotic combination cotrimoxazole have been specifically associated with ulcers on the top surface of the tongue.
Broader drug classes that can trigger oral ulcers include antibiotics, antiepileptics, diuretics, and antiretrovirals. If your tongue ulcers started around the time you began a new medication, that timing is worth mentioning to whoever prescribed it.
Systemic Diseases Behind Recurrent Ulcers
Tongue ulcers that keep coming back can sometimes signal a larger health issue. Inflammatory bowel diseases like Crohn’s disease and ulcerative colitis are linked to oral aphthous ulcers, as is celiac disease, where the gut’s impaired absorption leads to the nutritional deficiencies that trigger sores.
Behcet’s disease is a less common autoimmune condition where painful mouth sores are often the earliest and most recognizable symptom. These sores look like canker sores, starting as raised round lesions that quickly become painful ulcers. They typically heal in one to three weeks but keep returning. Behcet’s also causes genital sores, eye inflammation, and skin problems, so mouth ulcers appearing alongside any of those symptoms is a distinctive pattern.
People with HIV are also more susceptible to recurrent oral ulcers due to shifts in their immune cell balance.
When a Tongue Ulcer Needs Attention
Most tongue ulcers are harmless and heal within two weeks. The key warning sign is duration. Any single ulcer lasting longer than two weeks is considered chronic and should be evaluated, primarily to rule out oral squamous cell carcinoma. A cancerous ulcer on the tongue often appears as a single, persistent sore that doesn’t heal, may feel firm or raised at the edges, and is typically painless in its early stages, which is the opposite of a canker sore.
Three other situations call for further investigation: when your ulcer episodes are becoming more severe over time, when recurrent ulcers first appear after age 25 with no prior history, and when ulcers are accompanied by systemic symptoms like fever, weight loss, or fatigue. In these cases, bloodwork and sometimes a tissue biopsy help identify or rule out underlying conditions.