a man with a canker sore

What Is a Canker Sore?

Canker sores, also known as aphthous ulcers, are small lesions on the inside of the mouth or along the tongue. They are usually white or yellow in color, with a red area in the middle. Unlike cold sores, canker sores are not contagious, which means they cannot be spread through kissing or the sharing of food.

Canker Sore Symptoms

Most canker sores will form on or under your tongue, inside your cheeks or lips, at the base of your gums, or on your soft palate in the roof of your mouth. Before the canker sore actually appears, you might notice a burning or tingling sensation. There are different types of canker sores. The most common include:

  • Minor canker sores - These are the most common form of canker sores. They are usually very small and oval shaped, and they will typically heal without scarring within one to two weeks.
  • Major canker sores - This type of canker sore is less common. Major canker sores are larger in size and form deeper in the skin. They can also be extremely painful and take up to six weeks to heal, with the possibility of leaving extensive scarring.
  • Herpetiform canker sores - This kind of canker sore is the least common form and typically occurs later in life. Herpetiform canker sores generally form in clusters of 10 to 100 sores and may merge into one large ulcer. However, they will still heal without any scarring within one to two weeks.

If you are experiencing fever along with your canker sores, difficulty eating or drinking, new sores developing before the old ones are able to heal, or unbearable pain, consult with your doctor.

Canker Sore Causes

The exact reason why canker sores occur has not established, though there are many factors that may act as triggers. These include:

  • Food sensitivities – Sometimes specific foods can cause a canker sore flare-up, such as coffee, chocolate, eggs, strawberries, cheese, nuts, and acidic or spicy foods.
  • Inadequate diet – If your diet is lacking in zinc, folic acid, vitamin B-12, and/or iron, you are more susceptible to developing canker sores.
  • Bacteria – Sometimes your mouth will have an allergic reaction to certain bacteria in the mouth. One specific bacteria that commonly causes canker sores is helicobacter pylori, which is the same bacteria that causes peptic ulcers.
  • Injuries – Minor injuries in your mouth that result from dental work, brushing too hard, cheek bites, or impact-related sports injuries can lead to canker sores.
  • Toothpastes – Certain toothpastes and mouth rinses that contain sodium lauryl sulfate have the potential to cause canker sores.
  • Hormones – For women, menstruation cycles can cause hormone shifts which can lead to the development of canker sores.
  • Stress – Similarly, stress causes some hormones to spike which can also cause canker sores.

Canker sores have also been linked to other conditions and diseases, such as celiac disease, inflammatory bowel disease, Behcet’s disease, HIV/AIDs, and immune system conditions.

Canker Sore Treatments

While minor canker sores will go away on their own and therefore don’t require treatment, other larger and more painful sores will usually improve with some medical care. There are many different options when treating a canker sore, and the decision for treatment will depend on the severity and location of the sore.

There are several different mouth rinses that are available for your doctor to prescribe. These usually contain steroids and lidocaine in order to reduce the pain as well as the swelling. Your doctor might also prescribe an oral medication for more severe canker sores.

There are also other over-the-counter options that don’t require a doctor visit. These include pastes, creams, gels, or liquids that can help with the pain and speed up the healing process if they are applied soon enough. 

Last Updated: April 24, 2015