What are canker sores?
Canker sores (formally known as aphthous ulcers or aphthous stomatitis – aphtha means ulceration in Greek) are small, round or oval, shallow ulcers that form inside of the mouth. They have a clear outer boundary that is typically red and inflamed, while the interior is yellow or grey-tinged (1).
They are typically small, but in severe cases and especially in immunocompromised people, can grow quite large. They typically form on the soft tissue, like the inside of the lips/cheeks, but can also form on the hard palate.
Canker sores are not contagious and are benign. However, they are painful and unpleasant and can be a symptom of deeper issues. They typically heal on their own within 10 to 14 days.
Recurrent aphthous stomatitis (RAS)/ recurrent aphthous ulcers (RAU) may be diagnosed if someone has gotten minor canker sores at least three separate times within the last year (1). It is estimated to affect 2.5 billion people worldwide and an estimated 20% of the general population (2, 3).
Canker sores are the most common oral mucosal disease in humans (1).
What are some predisposing factors for the development of canker sores?
40% of people who get recurrent canker sores have a family history of them, so there is likely a genetic component (4).
One study found that AA and AC genotypes of the E-selectin rs5361 gene polymorphism and TAA haplotype (rs2205849, rs5361, and rs1805193) are strongly associated with recurring canker sores (5). This gene codes for a cell adhesion molecule, and it is hypothesized that these genotypes increase the accumulation of leukocytes within the epithelium.
Another study found an association between a toll-like receptor 4 gene (TLR4 rs10759931 AA polymorphism) and recurrent canker sores (6). Toll-like receptors are involved in innate immunity.
2. Local Trauma
Injuries to mouth tissue can trigger the development of canker sores in some people (3, 7).
- Biting yourself
- Dental procedures
- Getting poked by sharp foods, like tortilla chips
- Highly acidic foods
- Injections in the mouth
- Lip picking/cheek biting when stressed or nervous
- Poorly fitting dentures
- Sharp teeth irritating the soft tissue
- Toothbrush injury
3. Certain Medications
Medications that have been linked with the development of canker sores include (8, 9):
- Captopril (ACE inhibitor)
- Chemotherapy agent
- Gold salts
- NSAIDs (propionic acid, diclofenac, and piroxicam)
- Sodium hypochlorite
4. Nutrient Deficiencies
Deficiencies in iron, thiamine, riboflavin, B12, B6, and folate are linked to the development of canker sores, and people with canker sores are twice as likely to be deficient in these nutrients compared to healthy controls (4, 8, 10).
Zinc deficiency has also been identified as a potential root cause, likely due to zinc’s important role in immunity (11, 12). One study found that 28% of people with recurring canker sores were zinc deficient, compared to only 4% of healthy controls (13).
5. Food and Chemical Sensitivities
Canker sores can also be triggered by reactions to certain foods and/or chemicals (14). The sores tend to go away when reactive foods or chemicals are removed.
SLS (sodium lauryl sulfate) and dairy are commonly reported as triggers (7, 15, 16).
A case study was also published about a woman who got canker sores from diet cola and cinnamon toothpaste due to sensitivities to balsam of Peru flavoring (in the soda) and cinnamic aldehyde (in the toothpaste) (17). They resolved when she changed her diet and removed fragrances.
Elevated levels of TNF-alpha (a pro-inflammatory cytokine) are also linked to the formation of canker sores, further suggesting a role for hypersensitivity reactions (7).
6. Stressful Life Events
Canker sores are more likely to develop after periods of intense stress, such as studying for final examinations or undergoing an important job interview. Psychological stressors are an even greater risk factor than physical stressors like injury or illness (9).
One study found that experiencing a stressful life event increased the risk of developing a canker sore within the following year by almost 3 times (18).
7. Dysbiosis of the Mouth?
One study found that people who get recurrent canker sores tend to have higher levels of IgA in their salvia, even during remission, suggesting a higher level of immune activity, even at baseline. This may be due to the presence of certain microbes in the mouth that stimulate the immune system (19).
Other studies have found an altered proportion and diversity of bacteria living in the mouth in people with recurring canker sores, but it is unclear whether this is a cause or effect (20, 21).
8. Quitting Smoking
Smoking is actually linked to a lower risk of cancer sores, possibly due to the effects of nicotine. Nicotine patches may help reduce canker sores in people who recently quit smoking (22).
9. Low Immunity
Anything else that reduces the functioning of the immune system (such as undergoing a recent organ transplant) may also increase the risk of developing canker sores (23).
What conditions are associated with canker sores?
1. Celiac Disease
Celiac disease is associated with frequent canker sores. Canker sores can be the first and/or only symptom of celiac disease in some people (24).
Crohn’s disease and ulcerative colitis are both linked to the development of canker sores in the mouth (which makes sense, since similar ulcers form in the small intestine and colon in these conditions!) (25).
3. Viral Infections
Certain viral infections, including Epstein-Barr (EBV) (mono), cytomegalovirus (CMV), and coxsackievirus are associated with increased occurrence of canker sores, especially in people with weak immune systems (8).
4. Behcet’s Disease / MAGIC Syndrome / Neumann’s Bipolar Aphthosis
Behcet’s disease and its variants, MAGIC syndrome and Neumann’s bipolar aphthosis, are associated with the development of canker sores. Both of these conditions involve the emergence of ulcers throughout the body, often beginning in the mouth (26, 27).
PFAPA, a condition of unknown cause that is usually seen in young children, involves periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis. Canker sores are one of its symptoms (8).
6. Systemic Lupus Erythematous (SLE)
Lupus is an autoimmune disease that is also linked to canker sores. Approximately 21% of people with lupus get canker sores and their emergence is linked to greater disease severity and poorer prognosis (28).
7. Sweet’s Syndrome
Sweet’s syndrome, also known as acute febrile neutrophilic dermatosis, is a rare disease that causes sudden fever and skin lesions. It is associated with the development of canker sores (29).
8. Cyclic Neutropenia
Cyclic neutropenia is an inherited disorder (autosomal dominant) that causes cycles of having low numbers of white blood cells every 21 days. Canker sores tend to appear when neutrophil levels are low since they are an important part of the immune system (30).
Since HIV weakens the immune system, canker sores are more likely to develop and are usually larger and more severe (31).
What are the recommended nutrition interventions for canker sores?
1. Check for nutrient deficiencies (1)
- CBC to check for possible anemia (due to iron, B12, or folate deficiency)
- MMA for B12 deficiency
- RBC folate for folate deficiency
- Ferritin for iron deficiency
- RBC or serum zinc for zinc deficiency
One study found that taking 1,000 mcg of sublingual vitamin B12 daily for 6 months significantly reduced canker sore recurrence in people with RAS, regardless of whether they were initially deficient in vitamin B12 or not (32).
Zinc therapy (220 mg zinc sulfate, once per day before a meal, for one month) has also been shown to put recurrent canker sores in remission (33).
It appears that determining deficiencies and then repleting them is best, rather than just broadly giving a multivitamin-mineral supplement (a MVM supplement was shown to have no effect on canker sore frequency in one study) (2).
2. Rule out celiac disease
Since canker sores can be a sign of celiac disease, it may be a good idea to rule out celiac disease with antibody testing (only accurate if the person is still regularly eating gluten).
3. Keep a food log / try an elimination diet
If food or personal care products might be the trigger, keeping a food/symptom log and/or doing an elimination diet may help (34).
Trialing a cow’s-milk-free diet for two weeks is recommended, especially before undergoing treatments or taking medications that may have side effects (x). Goat’s milk may be a suitable substitute for some people (35).
4. Reduce stress
If stress is a trigger, reducing stress through things like meditation, exercise, proper sleep, journaling, hobbies, etc. is probably a good idea!
5. Support the immune system
Since immunodeficiencies and increased oxidative stress are linked to canker sores, supporting the immune system may help (this is just a theory, no specific studies have been done) (36, 37).
Proper nutrition, reducing stress, adequate sleep, resolving infections, and avoiding foods or environmental factors that trigger allergies or sensitivities are likely all important.
Since canker sores are associated with certain viral infections, it may be a good idea to check for them. Doctors can check for the presence of EBV, coxsackie, or CMV antibodies via Labcorp.
7. Provide symptom relief
Minor canker sores will typically heal on their own without treatment. Saltwater mouth rinses may be helpful to alleviate the pain (9). Topical analgesics with lidocaine are also sometimes used.
9. Supplements to promote healing
Deglycyrrhizinated licorice (DGL) can promote the healing of canker sores when used in mouthwash or as an oral patch (38, 39). A review of the literature found that the DGL patches are just as effective as the prescription therapy amlexanox (40).
One very small study found that applying virgin coconut oil topically to canker sores was just as effective as triamcinolone at reducing ulcer size and relieving pain, but more high-quality research is needed on this topic (41).
10. Consider the timing
People who get recurring canker sores typically develop their first one between the ages of 10 and 19 years old. If someone suddenly starts getting canker sores in their 20’s or later, systemic conditions, like autoimmune diseases, celiac disease, IBD, etc., should be ruled out (9).
Erica is a registered dietitian nutritionist and lover of science and learning. She has a never-ending passion for education, and gladly spends her time writing & growing this blog! When she’s not at the computer, she can be found in the kitchen with her family, rocking out to good music and cooking up a storm.