A mouth ulcer is a sore that appears anywhere inside your mouth, including your gums, lips, tongue, inner cheeks, or roof of your mouth. They are usually red, yellow, or white, and you might have one or several. Mouth ulcers are often painful and can make eating, drinking, and speaking uncomfortable. Other symptoms could include swelling around the ulcers, increased soreness when brushing your teeth, and pain that worsens when eating spicy, salty, or sour foods.

Mouth ulcers may occur for a number of reasons, including minor tissue injury from dental work, accidentally biting your cheek or tongue, an allergic reaction to certain bacteria, wearing braces or retainers, and aphthous ulceration. They can also be caused by viral, bacterial, and fungal infections, chemicals, and some medical conditions. Most mouth ulcers are harmless and resolve by themselves within 10 to 14 days. However, an ulcer that won’t heal may be a sign of mouth cancer.

It’s usually safe to treat mouth ulcers at home, although your pharmacist may advise that you see your GP or dentist if the ulcer lasts longer than three weeks or is extremely painful. Treatment options include using a soft-bristled toothbrush, drinking cool drinks through a straw, eating softer foods, getting regular dental check-ups, and eating a healthy, balanced diet. Your GP or dentist may prescribe stronger medicine to treat severe, persistent, or infected mouth ulcers, such as steroid mouth spray or tablets, painkilling gels, ointments, sprays, or tablets, and mouthwashes to kill or remove any germs in your mouth.