When am I most likely to develop a canker sore (aphthous stomatitis)?

Their exact cause is uncertain but some experts believe that immune system problems, bacteria or viruses may be reasons for developing canker sores. Another cause can be irritation from a loose orthodontic wire, a denture that doesn’t fit, or a sharp edge from a broken tooth or filling. Canker sores that last over a week should be seen by a dentist, as they can be the sign of a greater problem such as a disease or disorder. Mouth sores come in several different varieties and can have any number of causes.

Canker sores (aphthous stomatitis) can be triggered by factors such as emotional stress, lack of certain nutrients in your diet (especially iron, folic acid, or vitamin B12), menstrual periods, hormonal changes, and food allergies. They occur most commonly when you get a virus. Canker sores may occur after a mouth injury due to dental work, aggressive tooth cleaning, or biting the tongue or cheek. In some cases, the cause cannot be identified.

You can develop aphthous stomatitis (canker sore) for the first time at almost any age. However, most people report a first outbreak between 10 and 20 years of age. After a first outbreak, most people have recurrent outbreaks throughout life.