Mouth Sores

Mouth Sores

Also called: Oral Mucositis


Mouth sores can appear as blisters, open lesions (ulcers), inflammation or areas of skin discoloration. They may occur in a variety of locations in and around the mouth, including the lips, tongue, inner cheeks, gums, roof of the mouth (palate) or mouth floor.  

Mouth sores can occur due to a variety of causes. They may be the result of bacterial, viral or fungal infections. They may also stem from tissue injury (e.g., biting the lip or inner cheek) or chronic irritation (e.g., due to ill-fitting dentures, braces, tobacco or alcohol). Less commonly, mouth sores can occur as a result of immune system deficiencies, allergies, underlying medical conditions (e.g., cancer, autoimmune disorders), or as a side effect of certain medications.

Cold sores are one of the most common types of mouth sores. They usually appear outside of the mouth (e.g., on the lips) as blisters that ooze fluid and crust over. Cold sores can easily be passed from person to person. Canker sores are also very common, although they are not contagious and generally appear inside a person’s mouth. They are white or pale ulcers surrounded by a ring of reddened skin. Mouth sores can also appear as patches of white or gray skin inside the mouth, due to thrush or leukoplakia. 

Most mouth sores go away on their own within one or two weeks. However, patients should consult with a dentist or physician if they experience mouth sores that are severe, persist beyond two weeks or change in appearance.  

A dentist or other health care provider can usually identify the type of mouth sore by its location and appearance. Additional tests to detect or confirm the cause of mouth sores include x-rays, biopsies and blood tests.

Treatment generally focuses on alleviating the pain, discomfort or unpleasant appearance of mouth sores, and may include topical, oral or injectable medications. Other remedies include the use of mouth rinses and avoiding food and/or beverages that can irritate existing mouth sores.

There is no guaranteed method of preventing mouth sores. Because numerous factors can cause mouth sores, preventive techniques may depend on the specific condition causing the mouth sores. For example, antiviral medications may help prevent outbreaks of cold sores, but not canker sores.

In general, methods that may reduce the likelihood of developing mouth sores include practicing good dental hygiene, having regular dental examinations and exercising healthy eating habits, as well as avoiding potential irritants and people with contagious illnesses that can cause mouth sores.

About mouth sores

Sores that occur in the mouth can take many forms. They may be open lesions (ulcers), raised bumps or blisters, inflamed areas or patches of discolored skin. They can appear in many different areas of the mouth, including the lips, tongue, inner cheeks, gums, roof of the mouth (palate), under the tongue or on the mouth floor.

Mouth sores may develop after the mucous membranes lining the mouth come into physical contact with an irritant. They may also appear as a result of infection, allergies or disease.

Normally, there are a number of bacteria, viruses and fungi that exist in the mouth. Many in saliva help to break down food particles while chewing. Many different factors (including conditions inside the mouth or irritating substances) can cause an overgrowth of these microorganisms. The bacteria, viruses or fungi then destroy tissue within the mouth – creating the ulcers, blisters, inflammation or discoloration that appear as mouth sores. Although it is not common, mouth sores may occasionally leave scars.

Most often, mouth sores last for one to two weeks then go away on their own without treatment. Occasionally, they may last for months.  

In people with immune system deficiencies, however, mouth sores can be severe and even life-threatening. Failure to properly treat mouth sores may result in the spread of infection, dental problems (e.g., abscessed teeth and gums) and, rarely, oral cancer.

Patients with mouth sores should consult with a dentist or physician in any of the following circumstances:

  • Mouth sores have not healed after two weeks
  • Sores are extremely painful or bleed
  • Difficulty talking, chewing or swallowing occurs
  • Other symptoms (e.g., fever, rash, drooling) appear
  • There is a change in the appearance or nature of the sores

Other symptoms related to mouth sores

Mouth sores may be accompanied by other symptoms, depending on the cause of the sores. Additional symptoms that can occur in or around the mouth in patients with mouth sores include:

  • Pain or discomfort
  • Reddened skin
  • Itching
  • Burning sensation
  • Bleeding
  • Flaking skin
  • Bad breath
  • Foul taste in the mouth
  • Dry mouth
  • Reduction or loss of sense of taste

In addition, a person with mouth sores may also experience difficulty chewing, swallowing, talking or breathing as a result of the sores. Additional symptoms that may occur outside the mouth area include fever, fatigue, sore throat and swollen lymph nodes.

Types and differences of mouth sores

Mouth sores come in a variety of forms. The most common are:

  • Cold sores, also known as fever blisters. These are fluid-filled blisters that burst and develop an outer crust. They usually appear on or around the lips, but sometimes may appear inside the mouth. The blisters themselves can be painful, and are usually preceded by a tingling or burning sensation (called the prodrome stage). Cold sores are contagious and can be transmitted through direct contact with infected areas or secretions, including saliva. They may reappear during periods of illness (e.g., colds, fever), stress or after sun exposure in people who have previously had cold sores. Cold sores can also be transmitted during mouth to genital contact during a cold sore eruption.

  • Canker sores. These painful open lesions (ulcers) usually appear in the soft tissue inside the mouth – on the cheeks, tongue or at the base of the gums. Unlike cold sores, canker sores are not contagious, although they may recur in people who have had them. They are usually preceded by a tingling or burning sensation, and typically appear as pale or yellow sores with a red ring around each sore. Canker sores are also referred to aphthous stomatitis or recurrent mouth ulcers.

  • Discolored patches of skin. These may occur due to thrush or leukoplakia. Thrush is a yeast infection that occurs in the mouth, signaled by white patches in the corners of the mouth, on the inside cheeks, tongue, roof of the mouth (palate) and throat. Attempts to remove the white patches may reveal red, inflamed skin that is likely to bleed. The condition is not usually painful.

    Leukoplakia, on the other hand, involves white or gray areas that usually appear on the tongue, although it may also develop on the gums, inside of the cheeks or palate. Affected areas are not usually painful, although they may become sensitive to spicy foods, temperature or touch.

Mouth sores are different from tissue irritation or inflammation commonly seen in cases of gingivitis or periodontitis, both of which are due to the buildup of plaque on the teeth (resulting from poor dental hygiene) and may cause the gums to bleed.

Potential causes of mouth sores

Many mouth sores are caused by bacterial, viral or fungal infections. These may result from a disease, disorder or chronic irritation. In other cases, the exact cause of the sores is not known. The most common causes of mouth sores include:

  • Herpes simplex viruses. These viruses – primarily herpes simplex virus type 1, also known as HSV1 – cause cold sores and can remain in the body for a lifetime, reappearing during periods of illness, stress, trauma (including dental treatment) or sun exposure. Most people have been exposed to HSV1 at some point by the time of adulthood. Cold sores may occasionally be caused by HSV type 2, the form of herpes simplex that most commonly causes genital blisters, during oral to genital sexual contact.
  • Unknown. For example, the cause of canker sores is unclear, although various factors may play a role in producing these types of mouth sores. These factors include tissue injury or trauma, immune system weakness (e.g., during a cold or the flu), genetics, allergies, bacteria or viruses, stress, hormones (e.g., during menstrual periods) and vitamin deficiency. People with ulcerative colitis or Crohn’s disease also appear to have an increased risk of developing canker sores.
  • Fungi. A yeast infection known as thrush can cause mouth sores. It occurs due to an overgrowth of the Candida albicans fungus inside the mouth. The infection is also sometimes referred to as Candidiasis and is common in babies and people with compromised immune systems (e.g., people with diabetes, HIV/AIDS).
  • Leukoplakia. A condition that is usually caused by chronic irritation of the mucous membranes lining the mouth (e.g., due to tobacco and/or alcohol use, ill-fitting dentures). It may also be caused by a fungal infection. Sometimes the cause of the condition is unknown. Leukoplakia causes skin discoloration inside the mouth.

The mouth can become irritated by a number of factors, which can lead to mouth sores. Common causes of mouth irritation include:

  • Biting the cheek, tongue or lip
  • Tobacco (e.g., cigarettes, cigars, chewing tobacco)
  • Braces
  • Dentures that are new or do not fit properly
  • Sharp or broken teeth
  • Burns from hot foods or liquids

Less common possible causes of mouth sores include allergies, cancer, autoimmune diseases (in which the body’s immune system attacks its own tissues and organs – such as rheumatoid arthritis or lupus) and comprised immune systems (e.g., human immunodeficiency virus [HIV] or acquired immunodeficiency syndrome [AIDS]).

Mouth sores can also appear as a side-effect of various medications. These include:

  • Chemotherapy drugs
  • Steroids
  • Antibiotics (e.g., penicillin, streptomycin)
  • Aspirin
  • Barbiturates (used to treat insomnia)
  • Anticonvulsants (e.g., phenytoin)

Diagnosing causes of mouth sores

A dentist or other health care provider can usually identify mouth sores through visual examination of the affected area (e.g., lips, inner cheeks and gums). Most mouth sores (e.g., cold sores, canker sores, or those due to thrush or leukoplakia) can be diagnosed based on the unique appearance and location of the damaged tissue.

A medical history may be taken, including questions regarding current medications, dental hygiene practices and any additional symptoms experienced along with the mouth sores.

Although not usually necessary in otherwise healthy patients, additional tests may be performed. These tests may include:

  • X-rays. Radiographic images of the mouth that can reveal the internal structure of the area. X-rays may help identify the extent of infection or tissue damage in patients with mouth sores.
  • Oral brush biopsy. A quick and painless procedure in which a small brush is used to remove some tissue from inside the mouth, which is then analyzed in a laboratory. No anesthesia is required during this type of biopsy. This test helps to identify abnormal cells inside the mouth that may be responsible for a patient’s mouth sores.
  • Biopsy. Removal of a small tissue sample for laboratory analysis. This may sometimes be done in cases of discolored patches of skin (e.g., due to thrush, leukoplakia).
  • Blood tests. Blood is drawn, usually from a vein, and then analyzed in a lab. Blood tests can identify viral infections in patients with mouth sores.

Treatment options for mouth sores

There is no permanent cure for many of the most common types of mouth sores (e.g., cold sores, canker sores). Thus, treatment may focus on alleviating the pain, discomfort or unsightly appearance of these sores.

Home care remedies for mouth sores include:

  • Avoiding foods or beverages that may aggravate the mouth sores. This includes foods that are spicy, acidic (e.g., citrus fruits or fruit juice), sharp/crunchy (e.g., pretzels, potato chips) or too hot. Consuming alcohol or caffeine may also irritate the lining of the mouth.
  • Using straws. Drinking through a straw may prevent liquids from coming into contact with sensitive areas of the mouth.
  • Avoiding irritating the gums during dental hygiene. For example, teeth may be more comfortably cleaned using foam swabs or a soft-bristled toothbrush.
  • Rinse the mouth regularly. Swishing water in the mouth before spitting it out can help keep the area clean. Mouth rinses that contain alcohol should be avoided because they may cause a stinging sensation in the mouth. Antimicrobial mouth rinses may be used. Rinsing with saltwater can soothe canker sores or mouth sores as a result of thrush.
  • Applying ice. Applying ice chips to mouth sores may help alleviate pain.

Medications may be used to relieve the discomfort and shorten the duration of mouth sores. They are available by prescription or over-the-counter. The type of medication used will depend on the severity of a patient’s sores and their cause. For maximum effectiveness, medications should be used at the first indication mouth sores are developing. Medications include:

  • Topical anesthetic. May include numbing agents (painkillers) as well as those medications that provide a protective coating.
  • Systemic drugs. May include pills, injections or topical ointments of medications used to treat infection or inflammation (e.g., antivirals, antifungals, antibiotics, steroids). There are over-the-counter preparations that may help relieve canker sores. Over-the-counter pain relievers (e.g., aspirin, acetaminophen, ibuprofen) may also be used for pain and inflammation – although aspirin should not be given to children or teens due to an increased risk of developing Reye syndrome, a life-threatening condition.

If mouth sores include cancerous cells, they are usually surgically removed.

Prevention methods for mouth sores

There is no sure-fire way to prevent mouth sores. Preventive measures may depend upon the specific condition or infection that a person is attempting to avoid. For example, certain antiviral medications may be able to suppress an outbreak of cold sores during periods of increased susceptibility (e.g., prior to dental treatment, intense sun exposure). This type of medication may have no effect on canker sores because they may not be caused by viruses. Some studies have shown that ice chips and certain medicated mouth rinses may help to prevent mouth sores caused by chemotherapy.

Antifungal medications have been prescribed to prevent cases of thrush (which results in skin discoloration of the mouth). However, use is controversial since the Candida fungus that causes thrush appears to develop a resistance to this type of medication, making it ineffective after an extended period of use.   

In general, there are actions people can take to avoid the most common mouth sores, including:

  • Getting regular dental examinations. Periodic visits to a dentist can help identify any causes for concern in a patient’s mouth. A dentist may be able to smooth rough edges on sharp, pointed teeth that can irritate the lining of the mouth and cause mouth sores. Fixing ill-fitting dentures can also help alleviate tissue irritation in the mouth.
  • Practicing good dental hygiene. Proper daily brushing and flossing can help keep the gums and teeth healthy, and help to avoid infections that may cause mouth sores.
  • Avoiding potential irritants. By avoiding the products that can irritate the sensitive lining of the mouth, a person can prevent some types of mouth sores. Products to avoid include tobacco, very hot foods or beverages, alcohol, caffeine and foods that are acidic, spicy or hard and crunchy.
  • Using sunscreen. Applying sunscreen to the lips may help prevent an outbreak of cold sores during periods of sun exposure.
  • Maintaining good immune system health. Eating a balanced diet, drinking plenty of water, getting plenty of sleep, exercising moderately and keeping stress levels to a minimum can all help a person’s body fight infections that can lead to mouth sores. Vitamins and other nutritional supplements can also help.
  • Avoiding people with contagious illnesses. Staying away from people with infectious illnesses can help prevent infections that can cause mouth sores. This includes refraining from kissing or skin contact with people who are sick – especially anyone with noticeable cold sores.
  • Practicing good overall hygiene. This includes frequent hand-washing and not sharing foods, beverages, or personal belongings (e.g., lip balm, lipstick, toothbrush, razor) with others, which can spread infection that may cause mouth sores.

Questions for your doctor about mouth sores

Preparing questions in advance can help patients have more meaningful discussions with their dentists regarding their conditions. Patients may wish to ask their doctor the following questions related to mouth sores:

  1. What type of mouth sores do I have?
  2. What is causing my mouth sores?
  3. Will additional testing be necessary to determine the cause of my mouth sores? How do I prepare for these tests?
  4. Do my mouth sores indicate a more serious underlying condition?
  5. Are my mouth sores contagious? If so, for how long will I be contagious?
  6. Do I need treatment for these sores? What do you recommend?
  7. Are there over-the-counter medications or home remedies you recommend for me?
  8. Are there certain foods or beverages I should avoid while I have these sores?
  9. What changes should I report to you?
  10. How can I prevent these mouth sores in the future?
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