Mouth ulcers (often called canker sores) are small, painful breaks in the lining of the mouth that usually form when that lining is irritated or when the immune system overreacts locally.

What mouth ulcers are

  • Mouth ulcers are shallow sores that appear on the inside of the lips, cheeks, tongue, or gums, not usually on the outer lips.
  • They are common, usually harmless, and tend to heal on their own in 1–2 weeks, though they can be quite painful while present.

Main reasons we get them

In most people, ulcers are triggered rather than caused by a single disease.

  • Minor injury :
    • Accidentally biting your cheek or tongue.
    • Rubbing from braces, sharp teeth, rough fillings, dentures, or brushing too hard.
  • Immune and lifestyle triggers:
    • Stress, tiredness, and anxiety can change how the immune system behaves and make ulcers more likely.
* Hormonal changes (e.g., periods, pregnancy) can also trigger outbreaks in some people.
  • Nutritional factors:
    • Low levels of iron, vitamin B12, folate, zinc, or vitamin D are linked to recurrent mouth ulcers in some people.
  • Food and product irritation:
    • Certain foods like citrus, spicy foods, chocolate, nuts, coffee, and very salty or acidic snacks can irritate the lining and trigger ulcers in sensitive people.
* Toothpastes or mouthwashes containing sodium lauryl sulfate can irritate the mouth lining for some users.
  • Medications and habits:
    • Some medicines (for example certain NSAIDs and beta blockers) list mouth ulcers as a possible side effect.
* Smoking and other tobacco products can irritate the mouth, and some people notice more ulcers when they first stop smoking.
  • Underlying health conditions (less common):
    • Conditions like coeliac disease, inflammatory bowel disease (e.g., Crohn’s), Behçet’s disease, and immune problems can show up as frequent or severe ulcers.
* Infections (such as herpes simplex, some bacterial or fungal infections) can also cause painful mouth sores.

Why they hurt so much

  • The top protective layer of the mouth lining is broken, exposing sensitive nerve endings to air, food, and drinks, which makes them sting and burn.
  • Acidic, salty, or spicy foods and hot drinks can inflame the raw surface and intensify pain until healing is complete.

When to worry and see a doctor or dentist

Most mouth ulcers are benign, but medical or dental review is important if:

  • An ulcer lasts longer than about 2–3 weeks.
  • Ulcers are unusually large, very frequent, or come with fever, rash, weight loss, diarrhea, or feeling very unwell.
  • There is a hard, painless ulcer or patch that doesn’t heal, especially if you smoke or drink alcohol heavily (to rule out more serious causes).

Simple ways to reduce and prevent them

  • Be gentle with your mouth: soft toothbrush, slower chewing, and check that braces or dentures fit well.
  • Identify and limit personal triggers: common offenders include stress, specific foods, and certain toothpastes.
  • Ask a clinician about blood tests for iron and vitamin levels if you get frequent ulcers.
  • Use protective or soothing gels and mouthwashes specifically made for ulcers, and avoid very hot, spicy, or acidic foods while a sore is healing.

Information gathered from public forums or data available on the internet and portrayed here.