What Causes Canker Sores?

Dr. Jaudy explains the causes of canker sores.

In this article, I will discuss what canker sores are, different types of canker sores, and what causes them to appear.

Canker sores are usually gut related. What I mean by ‘gut related’ is enzyme deficiencies, nutritional deficiencies (including vitamin deficiencies), inflammatory bowel diseases (such as Crohn’s disease), celiac disease, Behçet’s disease, and many more. Basically, what happens in the gut happens in the mouth because these regions are physically, physiologically, neurologically, and chemically interconnected.

There are other causes of canker sores including swollen lymph nodes, decreased lymphatic drainage, decreased circulation, ingestion of toxicants or bacteria, emotional stress, and more.

We’ll talk more about these causes shortly, but first let’s talk about what canker sores are.

What Are Canker Sores?

Canker sores are small ulcers in the mouth or on the lips. An ulcer is a slow-healing sore on the surface of the mucous membrane. Ulcers are typically found in the gastrointestinal (GI) tract, including the intestines, stomach, esophagus, and mouth. In medical terminology, canker sores are referred to as aphthous stomatitis (‘aphthous’ meaning ‘mouth ulcer’ and ‘stomatitis’ meaning ‘inflammation of the mouth’).

More About Canker Sores

Canker sores may be recurrent, meaning that they constantly come and go. In fact, recurrent canker sores (recurrent aphthous stomatitis (RAS)) is the most common oral mucosal disease known to human beings. 1 There are three (3) main forms of RAS:

  1. Minor RAS in which the canker sores are recurrent, round, clearly defined, small, painful ulcers that heal in 10 to 14 days without scarring. 1
  2. Major RAS in which the canker sores are larger (greater than 5 mm), can last for 6 weeks or longer, and frequently scar. 1
  3. Herpetiform ulcers in which canker sores present as multiple small clusters of pinpoint lesions that can coalesce to form large irregular ulcers and last 7 to 10 days. 1

Lesions (canker sores) associated with RAS are not due to any single factor. Instead, they occur in a suitable environment that makes their development easier. Some of these factors include local trauma, smoking, stress, hormonal changes, family history, food intake and food hypersensitivity, medications and drugs, vitamin and trace element deficiencies, infectious factors, and immunological factors. 2 3

There are numerous diseases and disorders associated with canker sores. These include (but are not limited to):

  • Ulcus vulvae acutum 2
  • Mouth and genital ulcers with inflamed cartilage (MAGIC) syndrome 2
  • Fever, aphthosis, pharyngitis, and adenitis (FAPA) syndrome 2
  • Cyclic neutropenia 2
  • Celiac disease 3
  • Behçet’s disease 2 3 4
  • Crohn’s disease 5
  • Human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) 6 7
  • Vitamin deficiency (especially Vitamin B deficiencies) 8 9
  • Stevens-Johnson syndrome 10
  • Reiter’s syndrome 10
  • Problems in the immune system 11
  • And others

Canker sores are usually the result of an underlying medical condition, such as those listed above and others. However, other factors that may lead to canker sores include:

  • Physical, mental, or emotional stress 10 11
  • Chemical irritants 10
  • Viral infections 11
  • Mouth injury from dental work 11
  • Cleaning teeth too roughly 11
  • Biting the tongue or cheek 11
  • Hormonal changes 11
  • Oxidative stress 12
  • And others

With so many possible causes, it is easy to see why no single cause has been identified. Canker sores, especially those that are recurrent, are an indication of a systemic problem. All of the body’s systems interact and communicate with each other. This means that a problem in one region will likely cause problems in other regions. In the example of canker sores, we can see that underlying conditions (such as those mentioned above) cause more symptoms than each condition describes alone.

Now, consider this when you seek treatment for canker sores. Although there are numerous oral medications that can help to manage the symptom, you should ask yourself: What else is going wrong in my body if I have recurrent canker sores? You should also ask yourself: Are my canker sores related to my pre-existing condition? The answer to this second question is yes. Anytime you have a medical condition, the problem is not only in one area; it is global, meaning that it effects every function of your body. Although symptoms may seem unrelated, if they occur in the same person (such as you), they are intimately related, as is all of the functions of the body.

Furthermore, the underlying causes of most chronic conditions are neurological. Neurological misfiring causes organs, tissues, and glands to dysfunction, which can lead to a wide variety of symptoms and conditions, including many of the conditions listed above. When neurological signaling becomes aberrant, you can get decreased immune function, decreased enzyme production, decreased digestion, decreased heart, liver, and kidney function, altered hormonal and metabolic function, and more all of which can ultimately lead to many of the conditions described above and, of course, recurrent canker sores.


  1. Ship JA. Recurrent aphthous stomatitis: an update. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology 81.2 (1996): 141-147.
  2. Rogers RS. Recurrent aphthous stomatitis: Clinical characteristics and associated systemic disorders. Seminars in Cutaneous Medicine and Surgery. Vol. 16. No. 4. Elsevier Science, 1997.
  3. Natah SS, et al. Recurrent aphthous ulcers today: a review of the growing knowledge. International journal of oral and maxillofacial surgery 33.3 (2004): 221-234.
  4. Scully C, Porter S. Oral mucosal disease: recurrent aphthous stomatitis. British Journal of Oral and Maxillofacial Surgery 46.3 (2008): 198-206.
  5. Plauth M, Jenss H, Meyle J. Oral manifestations of Crohn's disease: an analysis of 79 cases. Journal of clinical gastroenterology 13.1 (1991): 29-37.
  6. Bach MC, et al. Aphthous ulceration of the gastrointestinal tract in patients with the acquired immunodeficiency syndrome (AIDS). Annals of internal medicine 112.6 (1990): 465-467.
  7. Kline MW. Oral manifestations of pediatric human immunodeficiency virus infection: a review of the literature. Pediatrics 97.3 (1996): 380-388.
  8. Piskin S, et al. Serum iron, ferritin, folic acid, and vitamin B12 levels in recurrent aphthous stomatitis. Journal of the European Academy of Dermatology and Venereology 16.1 (2002): 66-67.
  9. Nolan A, et al. Recurrent aphthous ulceration: vitamin B1, B2 and B6 status and response to replacement therapy. Journal of oral pathology & medicine 20.8 (1991): 389-391.
  10. Graykowski EA, et al. Recurrent aphthous stomatitis: Clinical, therapeutic, histopathologic, and hypersensitivity aspects. Jama 196.7 (1966): 637-644.
  11. National Institutes of Health (NIH) Medline Plus. Canker Sore. Accessed November 18, 2014. Available at: http://www.nlm.nih.gov/medlineplus/ency/article/000998.htm
  12. Arikan S, et al. Oxidant/antioxidant status in recurrent aphthous stomatitis. Oral diseases 15.7 (2009): 512-515.

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Comments: 1
  • #1

    Health Kidney (Wednesday, 23 August 2017 09:23)

    Very good points you wrote here..Great stuff...I think you've made some truly interesting points.Keep up the good work.