Mouth ulcers are sores that appear anywhere inside the mouth and are usually red, yellow, or white. They can be painful and make eating, drinking, and speaking uncomfortable. The most common causes of mouth ulcers include:

• Minor tissue injury from dental work, such as having a cavity filled.
• Accidentally biting your cheek or tongue.
• An allergic reaction to certain bacteria.
• 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. In most cases, mouth ulcers are harmless and resolve by themselves within 10 to 14 days without the need for treatment. However, if a mouth ulcer is large, extremely painful, or lasts for a long time without healing, it is best to seek the advice of a doctor or dentist.