A small, painful white or yellow sore inside the mouth can make eating, talking, and even smiling uncomfortable. Canker sores are common, not contagious, and usually heal on their own, but understanding what triggers them can help you get them less often.
Quick Answer
Canker sores are most often triggered by minor mouth injury, stress, certain foods, or nutrient deficiencies. They typically heal within one to two weeks and are not caused by a virus, unlike cold sores.
Common Causes of Canker Sores
Minor Mouth Injury
Accidentally biting your cheek, aggressive brushing, or irritation from braces can damage the delicate lining of the mouth, triggering a sore at the site.
Stress
Emotional stress is a well-documented trigger, likely linked to its effect on the immune system and the body’s inflammatory response.
Acidic or Spicy Foods
Citrus fruits, tomatoes, and spicy foods can irritate the mouth’s lining, particularly in people already prone to canker sores.
Nutrient Deficiencies
Low levels of vitamin B12, folate, iron, or zinc are associated with more frequent canker sores in some people.
Toothpaste Ingredients
Sodium lauryl sulphate, a foaming agent in many toothpastes, has been linked to increased canker sore frequency in sensitive individuals.
Hormonal Changes
Some people notice canker sores appearing around their menstrual cycle, likely linked to shifting hormone levels.
Food Sensitivities
Certain foods, including chocolate, coffee, and nuts, are reported triggers for some people, though sensitivity varies widely from person to person.
Underlying Conditions
Frequent, severe canker sores can occasionally be linked to conditions such as coeliac disease or inflammatory bowel disease, particularly when they occur alongside digestive symptoms.
How to Ease a Canker Sore
- Rinse with warm salt water or a saline mouth rinse several times a day
- Avoid acidic, spicy, or rough-textured foods while it heals
- Use an over-the-counter oral gel to reduce pain
- Switch to a toothpaste without sodium lauryl sulphate if sores are frequent
- Use a soft-bristled toothbrush to avoid further irritation
When to See a Doctor or Dentist
- A sore lasts longer than two to three weeks
- Sores are unusually large or extremely painful
- They appear very frequently, more than a few times a year
- You have a fever or feel generally unwell alongside the sores
FAQs
Are canker sores contagious?
No. Unlike cold sores, which are caused by a virus, canker sores are not contagious and cannot be passed to others.
How long do canker sores usually last?
Most heal within one to two weeks without treatment, though larger sores can occasionally take longer.
Can diet really trigger canker sores?
Yes, for many people. Acidic, spicy, or certain trigger foods can bring one on, particularly in those already prone to them.
Conclusion
Canker sores are usually linked to minor injury, stress, or diet, and heal on their own within a couple of weeks. Simple home care eases most cases, but sores that are unusually frequent, large, or slow to heal are worth mentioning to a dentist or doctor.
This article is for general information only and is not a substitute for professional dental advice. If sores persist beyond three weeks, please see a dentist.
