How Mouth Sores Develop

Mouth sores do not develop right away after the cancer treatment begins. For the first few days of chemotherapy or radiation, you probably won’t notice any changes in your mouth. However, after about three to five days, the soft tissues of the mouth may feel a little warm. There might also be some tingling and mild soreness that you notice at this time.

Sores may begin to appear within about a week and a half after the start of cancer treatment. Usually, the sores remain until after treatment stops. A week or two after treatment ends, the sores generally begin to heal. Usually, by the third week after treatment stops, the mouth sores and pain disappear. If your treatment has been very aggressive, you may experience more severe mouth sores that last longer.

Indications of Mouth Sores

  • Throat and mouth feel sore or tender
  • Small ulcers
  • Discomfort in the throat or mouth, especially when eating hot or cold foods
  • Shiny, swollen tissues in the mouth and on or under the tongue
  • Red, inflamed patches, sometimes with white spots
  • Sticky mucous or blood in the mouth
  • A white or yellow film in the mouth