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Canker Sores
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Mouth Teeth

Canker Sores

Canker sores are painful, non-contagious mouth ulcers that typically resolve on their own with time and symptom management.

Overview

Canker sores are small, round sores that appear inside your mouth, such as on the inside of your cheek, under your tongue, or in the back of your throat. They usually feature a red edge and a gray center and can be quite painful. It is important to note that they are not the same as cold sores, which are caused by herpes simplex.

Causes and Triggers

Canker sores are not contagious. While the cause is sometimes unknown, they may be triggered by several factors:

  • Viral infections
  • Stress
  • Food allergies
  • Lack of vitamins and minerals
  • Hormonal changes or menstrual periods

Management

In most cases, the sores go away by themselves. To manage discomfort, you may use ointments, creams, or rinses. Avoiding hot or spicy food while you have a sore can also help reduce pain.

Frequently Asked Questions

Canker sores appear only inside the mouth (cheeks, tongue, throat) and are not contagious. They are typically round or oval with a red border and a white or gray center. Cold sores, on the other hand, are caused by a virus, are contagious, and usually appear on the outside of the lips or around the mouth, though they can sometimes occur inside. If a sore is unusually large, lasts longer than two weeks, or is accompanied by fever or difficulty swallowing, it's best to see a doctor or dentist.
To relieve pain, you can use over-the-counter topical anesthetics or oral rinses containing ingredients like benzocaine or hydrogen peroxide. Rinsing with warm salt water or a baking soda solution (1 teaspoon baking soda in 1/2 cup warm water) can also help. Avoiding hot, spicy, acidic, or abrasive foods will prevent further irritation. For faster healing, ensure you're getting adequate vitamins, especially B12, folate, and iron, as deficiencies can be a trigger.
While triggers vary, some common ones include acidic foods (like citrus fruits, tomatoes), spicy foods, and abrasive foods (like potato chips). Stress is also a significant trigger, so stress management techniques may help. If you suspect food allergies, keeping a food diary can help identify culprits. Ensuring a balanced diet rich in vitamins and minerals, and using a soft-bristled toothbrush to avoid mouth injuries, can also reduce recurrence.
You should see a healthcare professional if your canker sore is unusually large, spreads, lasts longer than two weeks, causes extreme pain that interferes with eating or drinking, or is accompanied by a high fever. Recurrent canker sores that appear very frequently or in clusters also warrant a medical evaluation, as they could indicate an underlying health condition.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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