Most tongue sores are canker sores, small shallow ulcers that affect roughly 1 in 10 people and heal on their own within one to two weeks. But tongue sores can also result from accidental bites, infections, nutritional deficiencies, or, less commonly, something more serious. The cause usually becomes clear once you look at what the sore looks like, how long it’s been there, and whether anything else is going on in your body.
Canker Sores: The Most Likely Cause
Canker sores (aphthous ulcers) are the most common reason for a painful spot on your tongue. They’re round or oval with a white or yellow center and a red border, and they form on soft tissue: on or under the tongue, inside the cheeks or lips, or along the gum line. They are not contagious, and they’re not cold sores (which appear on the outside of the lips and are caused by a virus).
There are three types. Minor canker sores account for about 85% of cases. They’re small, oval, and heal without scarring in one to two weeks. Major canker sores are deeper, larger, and can take up to six weeks to heal, sometimes leaving scars. Herpetiform canker sores are the rarest (about 5% of cases) and appear as clusters of tiny pinpoint ulcers that can merge into one larger sore.
Common triggers include biting your cheek or tongue, dental work, brushing too hard, stress, and acidic or spicy foods. Some people get them repeatedly without a clear pattern. If that sounds like your sore, it’s almost certainly a canker sore, and it will likely resolve without treatment.
Injuries and Irritation
A sore that appeared right after you bit your tongue, burned it on hot food, or scraped it on a sharp chip or the edge of a tooth is a traumatic injury. These sores look red or raw, sometimes with a whitish coating as they heal, and the location usually lines up with the source of the injury. Rough dental appliances, braces, and ill-fitting dentures are frequent culprits. Traumatic tongue sores typically heal within a week or two once the irritation stops.
Infections That Affect the Tongue
Oral thrush is a fungal infection that produces creamy white patches on the tongue or inner cheeks. The patches look slightly raised, similar to cottage cheese, and can bleed if you scrape them. You might also notice a cottony feeling in your mouth, redness or burning, cracking at the corners of your lips, or a loss of taste. Thrush is common in babies, people who wear dentures, those taking antibiotics, and anyone with a weakened immune system. In otherwise healthy older children and adults, thrush is unusual enough that it warrants a visit to your doctor to check for an underlying cause.
Cold sores caused by the herpes simplex virus can occasionally appear inside the mouth, though they’re far more common on the lips. These start as fluid-filled blisters that eventually rupture and crust over. Unlike canker sores, cold sores are contagious and tend to recur in the same area.
Nutritional Deficiencies
If your tongue sore comes with a general burning sensation, redness, or a smooth and glossy appearance, a vitamin or mineral deficiency may be involved. Vitamin B12 deficiency is a well-documented cause of tongue problems. It can produce a condition sometimes called Hunter glossitis, where the tongue looks shiny and “lacquered” with a deep red color. Other oral signs of B12 deficiency include recurrent ulcers, burning of the tongue and lips, changes in taste, and tingling or numbness.
Oral changes show up in 50 to 60 percent of people with the type of anemia caused by B12 deficiency. Iron and folate deficiencies can cause similar symptoms. If you’re getting tongue sores repeatedly and your diet is limited, or if you have digestive conditions that affect nutrient absorption, a simple blood test can check your levels.
Autoimmune and Inflammatory Conditions
Recurring mouth ulcers that seem out of proportion to any obvious trigger can be a sign of a systemic condition. Behçet’s disease is a rare inflammatory disorder in which mouth ulcers are the first symptom in roughly 50 to 85 percent of cases. The ulcers look similar to canker sores (painful, round, under 10 mm, with a yellowish base and red halo) but tend to recur frequently, sometimes alongside genital ulcers, skin lesions, or eye inflammation. Behçet’s is uncommon in the U.S., affecting about 5 people per 100,000, but it’s far more prevalent in Turkey and the Middle East.
Inflammatory bowel diseases like Crohn’s disease and ulcerative colitis can also produce oral ulcers. Celiac disease is another possibility, particularly when mouth sores appear alongside digestive symptoms and don’t respond to typical treatments. In all of these cases, the mouth sores are a clue to a larger pattern of inflammation in the body.
When a Tongue Sore Could Be Cancer
This is the concern that brings many people to a search engine, and the key fact is straightforward: a sore on the tongue that doesn’t heal after two to three weeks needs professional evaluation. Tongue cancer, which usually starts in the flat cells lining the tongue’s surface, often first appears as a sore that simply won’t go away. Other warning signs include a red or white patch on the tongue, a lump or thickening, numbness, pain or difficulty swallowing, unexplained bleeding, and swollen lymph nodes in the neck.
Most tongue sores are not cancer. But because early-stage oral cancer can look deceptively harmless, the two-to-three-week rule is the standard benchmark that doctors and dentists use to decide when a closer look is needed. That closer look typically means a biopsy, where a small sample of tissue is examined under a microscope.
Relieving the Pain at Home
While your sore heals, over-the-counter oral anesthetics containing benzocaine (usually at 20% concentration) can numb the area temporarily. You apply the product directly to the dried sore and let a film form over it. Use it up to four times a day, and don’t continue for more than seven days without checking with a dentist or doctor.
What you eat matters too. Until the sore heals, avoid foods and drinks that irritate open tissue:
- Acidic foods like tomatoes and citrus fruits
- Very spicy foods
- Hard or sharp-edged foods like chips, raw vegetables, and crusty bread
- Hot foods and drinks
- Carbonated and alcoholic drinks
A saltwater rinse (half a teaspoon of salt in a cup of warm water) can also soothe irritation and help keep the area clean. Swish gently and spit.
Preventing Recurring Sores
If you get tongue sores frequently, look for patterns. Some people find that switching to a toothpaste without sodium lauryl sulfate (SLS), a foaming agent, reduces how often sores appear. Others notice flare-ups after eating certain foods, during stressful periods, or around hormonal changes. Keeping a simple log of when sores appear and what preceded them can reveal your personal triggers. Using a soft-bristled toothbrush and being careful during meals (eating slowly, avoiding talking while chewing) reduces the minor mouth injuries that set off canker sores in many people.
If your sores keep coming back despite these adjustments, or if they’re unusually large, painful, or slow to heal, your doctor may run blood tests to check for deficiencies in B12, iron, or folate, or screen for underlying inflammatory conditions. Most tongue sores are a nuisance, not a danger, but persistent ones deserve a closer look.