Mouth Sores: Causes, Symptoms, Diagnosis, Treatment and Prevention

They are painful ulcers found on the cheeks, lips, gums, tongue, the back of the mouth, and soft palate; sores can even develop in the esophagus.

These sores can be caused by various factors, ranging from stress to gastrointestinal diseases.

Symptoms of pain in the mouth usually include a burning or tingling sensation inside the mouth followed by painful and tender ulcers.

In more severe cases, sores in the mouth may be accompanied by swollen lymph nodes, physical fatigue, and fever.

Herpes simplex causes lesions on the lips or febrile blisters.

The sores in the mouth caused by herpes are very contagious, and they stop being when they are completely cured.


Multiple causes can cause sores in a person’s mouth, including mild cases to severe diseases.


Canker sores

There is no known cause for canker sores. They appear as light gray ulcers with a red outer ring. The sores in the mouth are formed by:

  • Biting cheeks, tongue, or lips.
  • Burns in the mouth when trying to eat hot foods or drinks.
  • Orthopedic appliances, dentures, or retainers cause tissue trauma.
  • Chewing tobacco or mucosal contact with irritating substances may also lead to consuming acidic foods and beverages.

Canker sores are not contagious, and the person may be more prone to them because of:

  • An immune system is weakened by illness or stress.
  • Deficiencies of minerals and vitamins.
  • Inflammatory diseases such as Crohn’s diseaseulcerative colitis, celiac disease, Behcet’s disease, and diseases related to a depressed immune system.

Occasionally, the sores in the mouth are the result of a reaction to:

  • Medicines.
  • Radiation or chemotherapy.
  • Autoimmune disorders
  • Bleeding disorders.
  • Cancer.
  • Bacterial, viral or fungal infections.
  • Lauryl (sodium sulfate, found in toothpaste and mouth rinses).
  • A weakened immune system due to AIDS or a recent organ transplant.

Herpes labial

Cold sores appear as small, fluid-filled ulcers around the lips.

They are caused by the herpes simplex virus and are highly contagious.

The virus can remain dormant for years after the initial infection and may reappear triggered by:

  • Stress.
  • Weakened immune system
  • Fever.
  • Fatigue.
  • Solar exposition.
  • Hormonal changes.

Symptoms of sores in the mouth

The sores in the mouth are usually a mild irritation and last only one or two weeks; they cause redness and pain.

They usually cause a tingling and burning sensation in the sore area.

Serious symptoms include:

  • Sores with a size of more than 1.5 cm.
  • High frequency of appearance of sores in the patient’s mouth.
  • Eruptions
  • Pain in the joints.
  • Fever.
  • Diarrhea.

The symptoms of cold sores include a sensation of itching and initial tingling around the lips, a rupture of small blisters, discharge of fluid after a burst blister, and finally, a scab.


Generally, sores in the mouth do not require a medical diagnosis.

However, the doctor should be consulted if:

  • White patches appear on the sores.
  • If you suspect herpes simplex or any other infection.
  • If the sores do not go away after a couple of weeks, they worsen.
  • When treatment is started (side effect of a medication).
  • When cancer treatment starts
  • If you recently had transplant surgery.

The doctor will perform a physical examination of the mouth, tongue, and lips.

If cancer is suspected, a biopsy and some tests may be done.


Soft mouth sores usually disappear naturally within 10 to 14 days but may last up to six weeks.

While the sores are present in the mouth, the following should be avoided:

  • Hot, spicy, salty, citrus foods with high sugar content.
  • Tobacco and alcohol.
  • Tighten or break sores or blisters.

It is recommended for the relief of symptoms:

  • Eat ice, ice cream, sorbets, or other cold foods.
  • Consume an analgesic.
  • Apply a thin paste of baking soda and water.
  • Apply a solution of one part of hydrogen peroxide and one piece of water.
  • Apply anti-inflammatory medications.
  • Apply gel with steroids.
  • When sores in the mouth are caused by viral, bacterial, or fungal infections, medications should be taken to treat the disease.
  • Eat foods that are easy to chew and swallow in small bites, and avoid raw vegetables and fruits and other hard, dry, or crunchy foods.
  • Avoid fruits and very acid juices, such as orange, grapefruit, lime, or lemon.
  • To speed up recovery, medications such as Maalox or milk of magnesia can be used, pouring the liquid over the painful area and rinsing the mouth with water after leaving for 15 to 20 minutes.

In those cases of cancer in the mouth, surgery or chemotherapy may be required.


The prevention of the appearance of sores in the mouth should be:

  • Avoid scorching foods and drinks.
  • Chew slowly, use a soft toothbrush and practice dental hygiene regularly.
  • Go to the dentist if any dental accessory or tooth irritates the mouth.
  • Decrease stress
  • Do not smoke or chew tobacco.
  • Protect the lips when exposed to the sun and use lip balms or sunscreens.
  • Check the mouth twice a day using a small flashlight and a trowel.
  • Brush the teeth with a soft bristle brush.
  • Rinse the toothbrush thoroughly with hot water after use and store it in a cool, dry place.
  • Use non-abrasive toothpaste that contains fluoride.
  • Clean dentures frequently and store them in an antibacterial solution. If the dentures fit poorly, you must make the necessary repairs to avoid irritation.