Canker Sores: The 25 Most Common Causes

Doctor Dialogue Healthy Living Nutrition

Canker sores are small, painful sores on the inside of your mouth. And if you ever experienced a canker sore, you are all too familiar with the discomfort that comes along with these painful (and unattractive) blisters — but what may surprise you, is that your canker sore indicates something more about your health.

Canker sores (also known as mouth ulcers) are among the most common types of oral lesions, affecting about 20 percent of people, according to the National Institute of Dental and Craniofacial Research.

While the exact cause of some canker sores hasn’t been pinpointed, some cases of canker sores are caused by an underlying health condition, some even deadly. From drinking too much coffee to arthritis, read on for what those annoying canker sores could be telling you about your body.

Key Canker Sore Causes to be Aware Of

1. A Food Sensitivity
People with a sensitivity to certain acidic foods such as tomatoes, strawberries or pineapple often develop painful canker sores.

2. Lyme Disease
According to, carriers of Lyme disease (an infection transmitted to humans by a deer tick) often list mouth ulcers as an early symptom.

3. A Reaction to Bacteria
Canker sores may also be your body’s reaction to a gastric infection or ulcer.

4. Hormones Affect the Mouth
Your period can be blamed for everything from cramping, bloating and feeling just plain miserable — but did you know that your cycle could also be to blame for canker sores? Studies show that the fluctuation of hormones during menstruation can be to blame for gum issues, like swollen gums and canker sores.

5. Inflammation is Linked to Canker Sores
Mouth sores are often the first symptom of Vasculitis, an inflammation of the wall of blood vessels, arteries, veins, or capillaries.

6. A Weakened Immune System
Canker sores could be the result of a faulty immune system that attacks healthy cells in your mouth instead of pathogens, such as viruses and bacteria.

7. A Gluten Intolerance Could Be to Blame
Studies have found that people with a hypersensitivity reaction to gluten were more susceptible to developing canker sores.

8. Coffee May be the Culprit
The thought of skipping your morning cup of joe may have you panicked, but your daily mug of coffee may be the cause of your canker sores. Coffeecontains salicylic acid, which can irritate your mouth causing those painful sores to pop up.

9. Stress Can Cause Mouth Sores
According to a 2005 study, when you get over-stressed, your mouth’s immune system has a tougher time protecting your delicate oral tissues from bacteria.

10. HIV Affects the Mouth
Canker sores can be an early symptom of HIV, with more than a third of people living with the disease developing mouth symptoms due to their weakened immune system, according to studies.

11. You May Be Zinc Deficient
Studies show that when you’re zinc deficient, your body can’t produce healthy, new cells, which can lead to the development of canker sores.

12. You May Be Arthritic
Reactive arthritis, a reaction to another infection within your body, is one of the more unexpected canker sore causes. It often can cause inflammation, which sometimes spreads to your mouth.

13. Canker Sores Could Indicate Lupus
The Lupus Research Alliance explains people suffering from this autoimmune disease, often cite canker sores (usually on the roof of the mouth) as one of their symptoms.

14. You Could Need Folic Acid
A diet low in leafy greens and fruits can be a reason for developing canker sores, since a folic acid deficiency is often linked to the mouth ulcers, according to Livescience.

15. A Reaction to Medication
A variety of mouth issues are common side effects of pain medications, and if you have reoccurring canker sores, the use of NSAIDs and beta-blockers could be the reason.

16. Oral Trauma
If you’re prone to canker sores, you may want to pass on the pretzels. Injury is a common causes of mouth sores, often caused by excessive tooth brushing, braces or chewing hard foods.

17. Canker Sores May Be a Skin Disorder
According to the National Organization for Rare Disorders, sweet syndrome is a skin condition includes symptoms such as painful skin and mouth lesions.

18. Your Toothpaste May Be the Cause
Research shows that the Sodium Lauryl Sulfate (SLS) in your mouthwashes and toothpastes, could lead to an increase of painful canker sore outbreaks.

19. Crohn’s Disease
While mouth sores aren’t a common symptom of Crohn’s (an inflammatory bowel disease), an inflammation from the disease can affect any part of the GI tract, including the mouth.

20. Canker Sores Could be in Your Genes
Those with a family history of canker sores are more likely to have severe canker sore outbreaks.

21. Get Your Rest to Avoid Canker Sores
Avoiding canker sores may be another good reason to get a good night’s rest.Research suggests that fatigue can sometimes be a trigger for canker sore outbreaks.

22. A Side Effect of Chemotherapy
According to the American Cancer Society, chemotherapy patients are especially prone to canker sores due to an inflammatory reaction to the treatment.

23. Nicotine Withdrawal
Besides common nicotine withdrawal symptoms, like headaches and irritability, smokers are also likely to develop canker sores for up to two weeks after quitting, according to a study published in the BMJ Journals.

24. Behçet’s Disease
Another rare cause of canker sores can be from uncommon disorders such as Behçet’s disease. The multisystem inflammatory disease is characterized by ulcers affecting the mouth and genitals, various skin lesions, and abnormalities affecting the eyes.

25. Canker Sores Could Be a Sign of Cancer
If your canker sores are accompanied by other symptoms such as a lump inside the mouth or neck and difficulty swallowing, it could be a sign of oral cancer.

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