What causes a scalloped tongue?

Look at the sides of your tongue in a mirror. If the edges have a row of rounded indentations, like a pie crust, that match the shape of your teeth, that is scalloping (also called crenated or indented tongue). The marks form when the tongue spends long periods pressed against the inner surfaces of the teeth, either because it is pushed there by habit or because there is not enough room for it.

Cleveland Clinic describes scalloping as not harmful on its own but a possible sign that something else is going on. A case report in PMC makes the same point from the other direction: scalloping is a useful visible clue that the tongue is swollen.

1. Clenching and grinding (bruxism)

Pressing the tongue against the teeth while clenching, often during sleep or concentration, leaves marks over time. Jaw ache, worn teeth or morning headaches are clues.

2. Sleep apnea

In obstructive sleep apnea the airway narrows during sleep, and the tongue may push forward against the teeth. A 2025 study in PMC found scalloping in 39.6% of people with obstructive sleep apnea compared with 20.5% of those without it. Loud snoring, gasping in sleep and daytime sleepiness alongside a scalloped tongue are worth discussing with a doctor.

3. TMJ problems

Jaw joint disorders can change how the tongue rests and are listed by Cleveland Clinic among causes.

4. A tongue that is large for the mouth

Some people simply have a broad tongue relative to their dental arch. True enlargement (macroglossia) has specific causes covered on its own page.

• Underactive thyroid (hypothyroidism): can cause tissue swelling, including the tongue, along with tiredness, weight gain, feeling cold and constipation, which the NHS lists as common symptoms.
• Dehydration: Cleveland Clinic lists it among causes of a swollen, scalloped tongue.
• Allergies and medicines: a PMC case report describes an older man whose tongue swelled and scalloped after taking a blood pressure drug; it resolved after the drug was stopped.
• Vitamin and mineral shortages: low B12, iron, niacin or riboflavin can make the tongue inflamed and swollen.
• Autoimmune and infiltrative conditions: such as Sjögren's syndrome, sarcoidosis and amyloidosis.
• Smoking: also listed as a contributing factor.

Treatment targets the cause rather than the tongue:

• A dentist can fit a night guard for grinding and check your jaw joints.
• Sleep apnea is diagnosed with a sleep study and often treated with CPAP or an oral appliance.
• Thyroid problems and deficiencies are confirmed with blood tests and treated with replacement.
• Drink enough water, avoid tobacco and manage stress, which drives daytime clenching for many people.

Once the cause is addressed, the indentations often become less pronounced, although long-standing ones may remain.

Cleveland Clinic suggests letting a provider know about a rippled tongue edge even if it does not hurt. It is rarely urgent. It becomes urgent if the tongue swells suddenly, especially with lip or throat swelling or difficulty breathing or swallowing, which can be angioedema or an allergic reaction.