Canker Sores/Mouth Ulcer: Symptoms, Causes, Risks, Complications, Diagnosis, Treatment and Prevention

Woman with Canker sores


Canker sores, also known as mouth ulcers or aphthous ulcers are painful lesions inside the mouth. They appear as shallow ulcers that appear on the gums, and these can make talking or eating uncomfortable. Though these lesions are small and may cause discomfort, they go away on their own and are not life-threatening.

There are two types of canker sores or mouth ulcers – simple (minor), complex (major) and herpetiform. Simple canker sores appear inside the mouth for about three to four times a year. They can last for up to one week and appear in people who are between the ages of 10 and 20 years old. On the other hand, complex canker sores are less common. However, they appear on individuals who have had them in the past. Herpetiform canker sores are not common and develop later in life. However, despite its name, this condition is not caused by the herpes virus.

Where do these canker sores usually appear? The painful and round mouth sores can show up on the inside of the lips, on the tongue, base of the gums, inside the cheeks and the palate. Canker sores are not life-threatening. However, these could signal an underlying health condition.


Canker sores or mouth ulcers are painful and open lesion inside the mouth. The lesions are usually yellow or white and are surrounded by inflamed and red soft tissue. The signs and symptoms of canker sores depend on which type the lesion belongs to:

Simple or Minor

The canker is most common and described as oval-shaped with a red edge, small, and can heal without scarring within two weeks.

Complex or Major

Major or complex canker sores are bigger, less common and deeper. They usually have defined borders and can be very painful. These lesions are less common than simple canker sores. These take longer to heal at about six weeks, and they could leave large scars.


These lesions are also uncommon and usually develop when a person reaches older adulthood. Despite its name, this condition is not a type of herpes virus infection. Unlike major canker sores, the herpetiform sores are pinpoint in size. These also emerge in group or clusters of 10 to 100 sores with irregular edges. Though there are abundant lesions, they do not leave scars and usually clear up in one to two weeks.

There are also other signs and symptoms that may be present when there is a canker sore:

  • Swollen lymph nodes
  • Fever
  • Fatigue

Generally, canker sores are not contagious, and they heal in one to three weeks even without any treatment. On the other hand, major canker sores or those which are larger and more serious may take up to six weeks to heal.


Though the exact cause of canker sores is still unclear, many researchers suspect that there are many factors that could contribute to the development of these lesions inside the mouth. Another problem people face is when they have recurrent canker sores, also dubbed as recurrent oral aphthous ulcers. The causes of this problem are also unclear, but there are various studies linking many factors such as allergies, family history, and viral infection.

Here are the various factors linked to the appearance of canker sores:

  • Stress
  • Hormonal changes
  • Food hypersensitivity (tomatoes and citrus fruits)
  • Drugs
  • Physical trauma to the lining of the mouth
  • Sharp tooth surface or the use of dental appliances like ill-fitting dentures and braces
  • Underlying health problems (for major canker sores) such as Crohn’s disease,
    celiac disease, gastrointestinal problems and an impaired immune system.
  • Infection (viral or bacterial)

4Risk Factors

There are many risk factors which will increase the likelihood of a person to develop canker sores. These risk factors include:

  • Family history or genetics of canker sores
  • Nutritional deficiencies of iron, folic acid, and vitamin B12
  • Inflammatory bowel disorders such as Crohn’s disease
  • Weakened immune system like in people with Acquired Immunodeficiency Syndrome (AIDS)
  • Behcet’s disease


Canker sores may disappear on its own without treatment. Usually, some people may feel a tingling or burning sensation for up to 24 hours before a lesion appears. These lesions may cause severe pain and eating foods which are sour or spicy may worsen the pain.

Some of the common complications of canker sores are fever, swollen glands, feeling a run-down and delayed wound healing in the case of people with underlying health problems. The good thing is, canker sores are not linked to further health risks. In worse cases, the canker sore may develop into stomatitis and oral ulceration.


Diagnostic tests are not needed to determine if a lesion is considered a canker sore. The doctor or dentist can identify the lesion just through a visual examination. A complete medical history is also recommended to determine other health problems which can worsen the patient’s current health status.

Some questions might be asked by the dentist or doctor such as:

  • Tobacco or alcohol use
  • Hormonal changes and fluctuations
  • Recent dental procedure
  • Food allergies
  • Impaired immunity
  • History of oral sexual intercourse and herpes virus infections


As with the other conditions affecting the mouth, an accurate diagnosis by a trained and licensed health care professional is necessary before the start of any treatments.

Though minor canker sores do not need any treatment to heal because they usually go away on their own, major canker sores are more serious. These may need treatment options to hasten their healing.

However, canker sores have no cure, but the treatment options may help decrease the symptoms and reduce the risk of their return. Here are treatment options for bigger canker sores:

Topical Agents

  • Silver nitrate– This agent can be applied directly to the lesion. Usually, after this agent is prescribed by a doctor, a health care professional will apply it to the lesion.
  • Benzocaine
  • Fluocinonide
  • Hydrogen peroxide

Before putting any medication on your canker sore, it is important to consult with a doctor, and all these medicines should be with a doctor’s prescription or permission.

Mouth Rinses

After being examined by a doctor, he may prescribe certain mouth rinses that contain the steroid dexamethasone. This will help reduce the pain and inflammation in the lesions area.

Oral Medications

When the canker sore does not respond to the other treatments and does not go away on its own, the doctor might prescribe oral medications. Some of the medicines used are oral steroid medications to reduce the pain and inflammation.

Nutritional Supplements

Some canker sores are caused by the deficiency of various vitamins and minerals. To curb the canker sore and prevent it from ever coming back is to treat the underlying cause. In this case, take nutritional supplements to correct whatever deficiency you have. Ask your doctor about the supplements he can recommend and prescribe for you.


  • Watch what you eat – Some foods may trigger the appearance of canker sores and in some cases, worsen the condition. There are people who are allergic to some foods, and this may cause canker sores.
  • Reduce stress – Since stress is a condition associated with canker sores, it would be a great help to reduce the stress levels by resting once in a while, relaxing and unwinding when given a chance.
  • Take your vitamins –To reduce the risk of developing mouth ulcers, it is important to consume the needed amounts of nutritional supplements, especially for those who are suffering from certain deficiencies. Many have studied shown the relationship of vitamin and mineral deficiencies such as B1, B2, B6, B12, iron and folic acid to the emergence of canker sore in some people.
  • Eliminate mouth trauma –When you have ill-fitting dentures or braces that are rubbing the brackets on your oral lining, you are prone to having mouth ulcers. The best way is to eliminate these or change them into more comfortable dental appliances.
  • Choose healthy foods –Aside from taking nutritional supplements, one way to make sure your vitamin and mineral levels in the body are adequate is through a well-balanced diet and the consumption of healthy foods.
  • Use an SLS-free toothpaste – Do not use toothpaste products with sodium lauryl sulfate or SLS for this leads to the irritation of the oral cavity lining.

9Canker Sores vs. Cold Sores

Are canker sores and cold sores the same? Although these two conditions are often confused with each other, they are not the same.

  • Cold sores are contagious while canker sores are not. Thus, kissing is one way to transfer the virus from one person to another.
  • Cold sores are caused by the herpes simplex type 1 virus, which is related to the one that causes genital herpes, while canker sores are caused by various factors like stress and food allergy.
  • Cold sores appear outside the mouth like under the nose, under the chin and around the lips while canker sores appear inside the mouth.
  • Treatments also vary because canker sores can go away on their own while cold sores need a treatment regimen prescribed by a doctor and to prevent it from coming back.