Your oral & dental health A-Z oral health information Mouth ulcers What are mouth ulcers? Ulcers are painful sores that appear inside the mouth. They are usually red or yellow. They are different from cold sores, which appear on the outer lips and are caused by a virus. What are the common causes of mouth ulcers? Usually a single mouth ulcer is due to damage caused by biting the cheek or tongue, or by sharp teeth, brushing or poorly fitting dentures. These ulcers are called ‘traumatic' ulcers. If you have a number of mouth ulcers, and they keep coming back, this is called ‘recurrent aphthous stomatitis'. How do I know if I have a traumatic ulcer? Traumatic ulcers are usually on their own, are next to the cause of the damage and go away once the source of the problem is removed. What are the signs of recurrent aphthous stomatitis? Recurrent aphthous stomatitis is a common problem, and is the repeated appearance of mouth ulcers in otherwise healthy children and young people. The cause is not known, but it is not infectious and is unlikely to be inherited. Are there different types of recurrent mouth ulcers? Yes. Minor ulcers are the most common. They can appear inside the cheeks, and on the lips, tongue and gums and, more rarely, on the roof of the mouth. Most of these ulcers are the size of the top of a pencil and can sometimes come in clusters. You can get four to six at any one time. Large ulcers are more severe and can take longer to heal. Any ulcer that lasts longer than 3 weeks should be checked by your dentist. Large ulcers may appear near the tonsils and can be very painful, especially when you swallow. You usually only get one at a time. It is also possible to have up to 100 very small, painful ulcers which last for one to two weeks. However, these last two varieties are very rare. You may get ulcers in other parts of the body such as your eyes or genital area. It is important to tell your dental team about this. What are the less common causes of mouth ulcers? Infections can cause mouth ulcers. Herpes simplex often causes mouth ulcers in children and some adults. Other less common viral and bacterial infections may cause mouth ulcers, but this is rare. Mouth ulcers can be caused by anaemia and occasionally by other blood disorders, and some skin or gastrointestinal diseases. Sometimes the mouth ulcers are the only sign of an underlying disease. Can cancer cause mouth ulcers? Cancer of the mouth can first appear as a mouth ulcer. The ulcers caused by mouth cancer are usually single and last a long time without any obvious nearby cause (for example a sharp tooth). Any ulcer that lasts longer than three weeks should be looked at by your dentist. Ulcers caused by cancer usually appear on or under the tongue, but may occasionally appear somewhere else in the mouth. Cancer of the mouth is usually linked to heavy smoking and drinking. Doing both together greatly increases the risk. Can I catch mouth ulcers? Mouth ulcers cannot be caught by kissing, or by sharing drinks and utensils. What types of treatment are there for mouth ulcers? The treatment depends on the cause of the ulcers. Sometimes all that is needed is for a sharp tooth to be smoothed down or a denture adjusted, although some patients may need mouthwashes or tablets. What should I do if I think I have mouth ulcers? If an ulcer lasts more than 3 weeks you should always ask your dental team or doctor for advice. They may be able to tell you the cause and provide treatment, or they may arrange more tests or refer you to a specialist if needed. How can I prevent mouth ulcers? You may be able to reduce the risk of mouth ulcers by: Keeping your mouth as clean and healthy as possible. Using high-quality toothbrushes (to reduce the risk of damage to your mouth). Eating a good diet which is rich in vitamins A, C and E, and includes foods such as fresh fruit and vegetables (to lessen the risk of mouth cancer). Regularly visiting your dentist. Should I worry about my ulcers? Most ulcers heal up on their own. However, if they don't heal within three weeks you should visit your dentist. Your dental team will be able to examine your mouth to check that the problem is an ulcer and not something more serious such as mouth cancer. If you suffer from ulcers that come and go often, you should visit your dental team to check that there is not an underlying medical cause. Always see your dental team or doctor if: The ulcer lasts for more than 3 weeks. You are unwell. The ulcers keep coming back. People who viewed this page also visited... Cold sores Mouth cancer Diet Need more advice? If you need free and impartial advice about your oral health, contact our Dental Helpline by email or call 01788 539780 (local rate call in the UK). Our Dental Helpline is completely confidential and has helped almost 400,000 people since opening over 20 years ago. Contact our experts by telephone, email or online enquiry, Monday to Friday, 09:00 - 17:00.