Are canker sores contagious?

Canker sores are not contagious, according to WebMD. While their specific cause is not known, canker sores tend to develop in individuals during periods of high stress or following consumption of acidic foods or beverages. Canker sores also commonly occur during female menstrual periods.

MedlinePlus explains that canker sores may also be caused by mouth injuries due to overzealous brushing habits or dental procedures. Iron and vitamin B-12 deficiencies can also trigger canker sores. Canker sores present as small red bumps on the cheeks, lips or tongue that eventually ulcerate. The sores typically heal on their own within 10 days but may cause additional symptoms such as swollen glands and fever.