When a strange bump appears in your mouth, it can be easy to leap to conclusions. There are many different causes for mouth lesions, though. Some are serious, some are not. An aphthous ulcer falls into the latter category. Even if they are not on the serious end of the spectrum, they can make life painful when they occur.

What is an aphthous ulcer?

An aphthous ulcer, commonly referred to as a canker sore, is a non-cancerous, recurring ulcer that forms in the soft tissues of the mouth. They appear anywhere in the mouth with the exception of the gums, the hard palate, and the very back of the tongue.

Approximately 20% of the population in the U.S. suffers from aphthous ulcers, with the usual onset in childhood. These ulcers appear anywhere between three and six times annually. The outbreak duration is between seven and ten days. For some unfortunate folks with severe aphthous ulcers, their outbreaks may be nearly constant, with new ulcers forming before the old ones heal. This results in chronic pain and difficulty eating that may, over time, lead to malnutrition and unwanted weight loss.

Types of aphthous ulcers

There are three main types of aphthous ulcers:

  • Minor
  • Major
  • Herpetiform

Minor ulcers are smaller and shallower, generally appearing by themselves. Major aphthous ulcers are deeper and larger. Herpetiform aphthous ulcers occur more frequently and involve the vascular system.

Regardless of the type, aphthous ulcers appear first as a flat, reddened area in the mouth that develops a flat, white or yellow-tinged disc that can be wiped away. When wiped away, a characteristic red halo remains. Some people contract one aphthous ulcer at a time, while others may experience them in multiples (sometimes hundreds at a time).

What causes an aphthous ulcer?

Aphthous ulcer causes are general and not very conclusive. In other words, most people cannot pinpoint just one cause or single moment when they appeared.

Generally, most people become aware of their oral aphthous ulcers as they get older, but they may have been present since childhood. A number of predisposing factors increase the risk of developing aphthous ulcers.


Approximately 40% of people with aphthous ulcers have a family member with this condition as well. Additionally, patients whose families have aphthous ulcers usually have more severe outbreaks.


Trauma that can lead to these ulcers include:

This is more likely to occur when other predisposing factors are present.

Gluten sensitivity, celiac disease, and inflammatory bowel disease

As autoimmune disorders, the three conditions above are often accompanied by aphthous ulcers.

In some cases, people who have aphthous mouth ulcers may also have one of the above diseases without knowing it. A gluten-free diet may help, but more research is needed.

Other autoimmune disorders

HIV/AIDS and other autoimmune disorders increase the chances of developing aphthous ulcers. This may be linked to the body’s decreased ability fight infection.

There are other rare causes such as PFAPA syndrome in children and vitamin deficiencies. Vitamin deficiencies may be associated with the inability to take in proper nutrition. In other words, it is hard to know if vitamin deficiency is an effect or a cause.

What triggers aphthous ulcers?

An outbreak of aphthous mouth ulcers can be triggered by:

Are aphthous ulcers contagious?

Aphthous ulcers are not contagious in any way and are not transmissible orally or via sexual contact. A person contracts aphthous ulcers at a young age and keeps them to themselves for their entire life.

What are common aphthous ulcer symptoms?

As with other mouth sores, aphthous ulcers symptoms begin with a prodromal phase that signals an impending outbreak. This phase features tingling, redness, burning, itching, and sometimes pain. Aphthous ulcers may follow this phase by mere hours, or they may appear the following day.

Pain is the main aphthous ulcer symptom, followed by the appearance of a lesion (as described above). Pain can increase over days, eventually beginning to subside as the ulcer begins to disappear.

Treatment and prevention of aphthous ulcers