What Causes Canker Sores?

A canker sore is a small aphthous ulcer that can appear inside the oral cavity, including the inner surface of the lips and cheeks, base of the gums, tongue, or soft palate. Normally, only one will appear at a time, although they can occur in a small group. The ulcers start off as a bump with a yellow or white center, which ends up bursting, leaving a small open lesion. While these sores can cause discomfort and pain, they are not contagious. Most people who suffer from these sores find that they generally last for a week or two and heal on their own.

Types of Canker Sores

Minor: These are the most common and are very small in size (less than half an inch in diameter). They generally heal within one to two weeks and cause no scarring.

Major: These sores are far less common and are typically larger than a half an inch in diameter. The average healing time is about six weeks and they can result in noticeable scarring.

Herpetiform: These are smaller than minor sores (about an eighth of an inch), however, they tend to form in clusters of as few as 10 or as many as 100. Much like minor canker sores, herpetiform sores heal without scarring within one to two weeks. Despite the name, this type of sore is unrelated to the herpes simplex virus and cold sores.


what causes canker sores?The primary symptoms are a visible lesion and pain associated with it. However, some individuals may experience fever, fatigue or listlessness, and swollen lymph nodes. If you develop an unusually high fever that accompanies the sore, you should seek medical attention immediately. You should consult a doctor as soon as possible if:

  • The sores are unusually large and last for more than three weeks
  • The pain does not diminish with any self-care remedies
  • The sores recur before the previous ones have completely healed

Your doctor may perform specific tests to rule out other issues. Although canker sores are not cancerous, they can resemble a type of mouth ulcer called squamous cell carcinoma, which can be distinguished from ordinary mouth lesions through a biopsy. Recurrent canker sores may be related to drug allergies, a skin disorder called erythema multiforme that occurs due to allergic infections, or bullous lichen planus, a somewhat rare disease affecting the tongue, skin, and mouth.

Underlying Causes and Risks

If you have ever experienced a painful canker sore, you have likely wondered what causes them and if there are ways to prevent them. Doctors and researchers have not reached a clear consensus on the causes. However, it has been determined that several factors can contribute to outbreaks. These factors include:

  • Injury to the mouth that results from a sports injury, accidentally biting the tongue, lip, or cheek, or dental work
  • Food sensitivities or allergies to coffee; eggs; highly acidic, fried or spicy foods; dairy products; chocolate; etc.
  • Eating hard foods like pretzels and potato chips
  • Chronic stress and fatigue from overwork or other life issues
  • Extreme or sudden weight loss
  • Viral infections
  • Crohn's disease, an inflammatory bowel disease associated with inflammation of the lining of the digestive tract
  • Brushing teeth hard enough to produce scrapes on the gums and other oral tissues
  • A deficiency in specific vitamins such as iron, folic acid, zinc, or vitamin B-12
  • HIV/AIDS and other diseases that cause the immune system to shut down or not properly function
  • Celiac disease, an intestinal disorder that is characterized by sensitivity to gluten
  • Behcet's disease, a very rare disorder that causes inflammation in the mouth and throughout the body
  • Toothpastes and mouth rinses that contain the cleaning agent sodium lauryl sulfate (SLS)

No conclusive evidence points to canker sores being inherited, although some research has shown that about one-third of individuals with recurring sores have a shared family history. While there may be a genetic connection, this could be attributed to other shared factors including allergens and other disorders. In addition, women appear to be more susceptible, especially to the herpetiform classification.

TheraBreath toothpastes do not contain SLS, so they are an optimal choice to prevent abraded tissue loss associated with canker sore development.

For more information on prevention and treatment, click here.

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