Mouth ulcers are painful sores that appear anywhere inside the mouth and can make eating, drinking, and speaking uncomfortable. Here are some common causes of mouth ulcers in adults:

• Minor tissue injury from dental work, such as having a cavity filled.
• Accidentally biting your cheek or tongue.
• Wearing braces or retainers.
• Using harsh or abrasive toothpaste.
• Eating lots of acidic foods, such as oranges, pineapples, and strawberries.
• Hormonal changes during your period.
• Stress.
• Lack of sleep.
• Certain health conditions, including many autoimmune diseases, can also cause mouth ulcers. These conditions may include vitamin deficiencies, viral, bacterial or fungal infections, Crohn’s disease, celiac disease, reactive arthritis, and lupus.

Most mouth ulcers are harmless and resolve by themselves within 10 to 14 days without the need for treatment. However, if a mouth ulcer lasts longer than two weeks, is extremely painful, or keeps coming back, it is best to see a doctor or dentist, as it may be a sign of a more serious problem.