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Mouth Sores: Why They Occur and How to Treat and Prevent Them

There are several types of mouths sores that can develop in different areas of the mouth. They may appear as raised bumps or blisters, ulcers (open lesions), inflamed areas or patches of discolored skin. Mouth sores can affect the lips, inner cheeks, tongue, gums, palate (roof of the mouth) or the mouth floor. They may develop after the mucous membranes lining the mouth come into direct contact with an irritant or as a result of allergies, infection or another disease.

A number of bacteria, viruses and fungi live in the mouth. Those in saliva, for example, help to break down food while we are chewing. However, certain factors can cause an overgrowth of these microorganisms, which then destroy tissue within the mouth, creating mouth sores.

In most cases, mouth sores last for one to two weeks and then go away on their own without any medical intervention. But occasionally, they may last for months. However, in people with compromised immune system, mouth sores can cause severe and even life-threatening complications. Failure to properly treat mouth sores may lead to the spread of infection, dental problems and, in rare cases, also oral cancer.

Patients with mouth sores that have not healed after two weeks, or are extremely painful or bleed, or suddenly changed their appearance, or those having difficulty chewing, swallowing or talking because of mouth sores, or when experiencing other associated symptoms such as rash, fever or drooling, should consult with a physician or dentist.

Symptoms that May Be Related to Mouth Sores

Depending on the cause of the mouth sores, they can be accompanied by other symptoms that may occur in or around or outside the mouth. These include:

  • Reddened skin
  • Burning sensation
  • Itching
  • Flaking skin
  • Pain or discomfort
  • Bleeding
  • Foul taste in the mouth
  • Reduction or loss of sense of taste
  • Dry mouth
  • Bad breath
  • Difficulty chewing, swallowing, talking or breathing
  • Fever, sore throat, fatigue or swollen lymph nodes

Types of Mouth Sores

Mouth sores can take many forms. The most common include:

Cold sores (fever blisters) are blisters filled with fluid that burst and form an outer crust. They typically develop on or around the lips, but occasionally may also appear inside the mouth. The blisters may be painful and are often preceded by a burning or tingling sensation as they grow. Cold sores can be transmitted through physical contact with infected areas or body fluids. They often recur during periods of illness, periods of elevated stress or after sunburn.

Canker sores (aphthous stomatitis or recurrent mouth ulcers) are painful ulcers (open lesions) that mostly develop in the soft tissue inside the mouth, forming on the cheeks, tongue or at the base of the gums. They typically occur as pale or yellow sores with a red ring around each sore. This type of mouth sores is not contagious. However, just like cold sores, canker sores may reappear in patients who have previously had them. As they develop, canker sores are often preceded by a burning or tingling sensation.

Discolored patches of skin may develop as a result of thrush or leukoplakia. Thrush is a yeast infection of the mouth, characterized by white patches in the corners of the mouth, tongue, on the inside cheeks, palate (roof of the mouth) and throat. Attempts to remove the white patches may reveal red, inflamed skin that is prone to bleed. This type of mouth sores is usually not painful. Leukoplakia, the other possible cause of discoloured patches of skin, involves white or grey areas that typically appear on the tongue, although it may also affect inside of the cheeks, palate or the gums. Affected areas do not tend to be painful but they may become sensitive to temperature, spicy foods or touch.

Mouth sores should not be confused with tissue irritation or inflammation commonly associated with periodontitis or gingivitis, both of which are due to the plaque build-up on the teeth and may eventually cause the gums to bleed.

Causes of Mouth Sores

Bacterial, viral or fungal infections are the leading cause of many mouth sores. These infections can be a result of a disease or chronic irritation. However, the exact cause of the mouth sores is not always known. The best known causes include:

Herpes simplex viruses, mainly herpes simplex virus type 1 (HSV1), trigger cold sores. They typically remain in the body for a lifetime, recurring during periods of stress, trauma, illness, or after sunburn. Cold sores that cause genital blisters may be caused by HSV type 2, which is transmitted during oral to genital sexual contact.

Fungi. The aforementioned yeast infection called thrush is a common cause of mouth sores. It is a result of an overgrowth of the Candida albicans fungus inside the mouth. This infection is sometimes referred to as Candidiasis. It is common in people with immune system deficiencies and in babies.

Leukoplakia is a condition that is mostly due to chronic irritation of the mucous membranes lining the mouth. It is one of the leading causes of skin discoloration inside the mouth. Leukoplakia may be also caused by a fungal infection. Sometimes the cause of this condition is unclear.

Unknown. The exact cause of certain types of mouth sores, such as canker sores, is unknown. Various factors may come into play, including compromised immune system, allergies, tissue injury or trauma, bacteria or viruses, genetic predisposition, stress, hormonal changes and vitamin deficiency. Patients with Crohn’s disease and ulcerative colitis also seem to be prone to developing canker sores.

Common causes of mouth irritation, which can lead to mouth sores include:

  • Biting the lip, cheek or tongue
  • Burns from hot liquids or food
  • Tobacco
  • Dentures that are new or do not fit properly
  • Dental braces
  • Sharp or broken teeth

Less common causes of mouth sores are allergies, autoimmune diseases, weak immune system, cancer and side-effects of various medications.

Diagnosing Mouth Sores

A dentist or a physician can in most cases diagnose mouth sores through visual examination of the affected area based on the appearance and location of the damaged tissue. Although rarely needed in otherwise healthy patients, additional tests may be ordered, including:

  • X-rays help reveal the internal structure of the area and may be used to identify the extent of infection or tissue damage in patients with mouth sores.
  • Biopsy is a removal of some tissue for laboratory analysis which may sometimes be done in cases of discolored patches of skin.
  • Oral brush biopsy is a simple procedure in which a tissue sample from inside the mouth is taken with a small brush and analyzed in a laboratory. It helps to identify abnormal cells inside the mouth that may be causing mouth sores.
  • Blood tests are used to identify viral infections in patients with mouth sores.

Treatment of Mouth Sores

Since no permanent cure for many of the common types of mouth sores exists, the focus of the treatment is on relieving the pain, discomfort or unsightly appearance of these sores. The best-proven home-care remedies for mouth sores are:

  • Rinsing the mouth regularly in order to keep the area clean. Antimicrobial mouth rinses may be used but rinses that contain alcohol should be avoided. Saltwater can help soothe sores resulting from thrush.
  • Avoiding unnecessary irritation of the gums during dental hygiene.
  • Avoiding spicy, acidic, very hot and crunchy foods or beverages that may exacerbate the mouth sores. Caffeine and alcohol may also irritate the inner lining of the mouth.
  • Drinking through a straw may prevent irritating beverages from coming into contact with sensitive or affected areas of the mouth.
  • Applying ice chips to mouth sores may help relieve pain.

Prescription or over-the-counter medications may be used to alleviate the discomfort and shorten the duration of mouth sores. For maximum effectiveness, medications should be used at the first indication mouth sores are developing. The type of medication depends on the cause and severity of mouth sores and they may include:

  • Systemic drugs which include pills, topical ointments or injections of medications for treating infection or inflammation. These may involve antibiotics, antivirals, antifungals and steroids. Over-the-counter pain killers such as aspirin, paracetamol (acetaminophen) or ibuprofen may also be used to relieve pain and inflammation. However, aspirin should not be given to children and teens.
  • Topical anesthetics including numbing agents and medications that provide a protective coating.

Mouth sores containing cancerous cells usually need to be surgically removed.

Prevention of Mouth Sores

At the moment there is no guaranteed way of preventing mouth sores. Preventive measures depend upon the specific condition or infection causing the mouth sores. For instance, certain antiviral medications may be used successfully to suppress an outbreak of cold sores during periods of increased susceptibility but they may have no effect on canker sores because these sores may not be caused by viruses.

However, there are certain actions people can take to avoid developing the most common mouth sores. These include having regular dental examinations and practicing good dental as well as overall hygiene, using sunscreens, exercising healthy lifestyles in order to maintain strong immune system, avoiding potential irritants and people with contagious illnesses that can cause mouth sores.