There are many potential causes of mouth sores. When these sores appear, they are often painful and can make everyday activities, such as brushing the teeth or eating hot food, more difficult.

In most cases, mild irritation causes a sore to appear. Avoiding the irritant can help a person prevent mouth sores in the future.

In other cases, sores form due to underlying health conditions. As some mouth sores can be contagious and may require treatment, anyone who is concerned about chronic or long-lasting sores should speak to a doctor.

In this article, learn about the possible causes of mouth sores as well as the treatment options.


Most mouth sores occur as a result of irritation. Many things can irritate the mouth and lead to sores, including:

  • poorly fitting dentures
  • a sharp or broken tooth
  • braces or other devices, such as retainers
  • burning the mouth on hot food or beverages
  • tobacco products

In other cases, mouth sores may develop due to:

Medical conditions and diseases that cause mouth sores include:

  • Candidiasis, or oral thrush, which is a fungal infection that causes white and red patches to appear in the mouth.
  • Herpes simplex, which causes cold sores on the mouth and can also produce genital sores.
  • Lichen planus, a chronic condition that causes an itchy, inflammatory rash in the mouth or on the skin.
  • Chronic canker sores, which have a red, flat edge and white or greyish patches surrounding them.
  • Gingivostomatitis, a common infection that is particularly prevalent in children. The sores are similar to canker sores, but they occur alongside symptoms of a cold or the flu.
  • Hand, foot, and mouth disease, which causes small, painful red patches to appear on these parts of the body. It is most common in children.
  • Leukoplakia, which causes white-grey patches to appear nearly anywhere in the mouth.
  • Autoimmune diseases, which may cause mouth sores to form.
  • Erythroplakia, a red patch that appears on the floor of the mouth and can be cancerous or precancerous.
  • Oral cancer, which can cause sores and lesions in the mouth.



In most cases, a person can determine the cause of their mouth sore themselves. For example, a person who has had a canker sore before will recognize another one if it appears.

A person who bites their cheek will know that the sore came from this incident. People with diagnosed conditions, such as herpes of the mouth, may recognize their symptoms and have a plan of action to address the flare.

If a person has recurrent or unexplained mouth sores, a doctor may be able to identify the cause of the sores by carrying out a visual check. They may also perform some tests, such as swabs and blood tests.

If a doctor suspects that a sore is the result of serious illness, they are likely to perform a biopsy of the area to test for the presence of cancer or other health issues.


In many cases, mouth sores will heal without treatment. Sores from minor injuries will typically clear within 1–2 weeks.

While their sores are healing, people can try:

  • gargling with salt water
  • excluding hot or spicy foods from their diet
  • abstaining from using tobacco products
  • avoiding alcohol
  • avoiding eating citrus fruits or salty foods, as they may cause sores to sting
  • using mouthwash
  • taking oral pain relievers
  • applying baking soda and water to the sore

If home remedies are not enough or the sore does not heal on its own, a person may wish to talk with their doctor about further treatment options.

A doctor can prescribe stronger anti-inflammatory or pain-relieving medications and ointments. If an underlying condition is causing the mouth sores, a doctor will develop a treatment plan for this too.


man holding mouth in pain due to mouth sores
People can avoid getting mouth sores by chewing carefully, practicing good dental hygiene, and avoiding smoking.

Some steps that a person can take to help prevent mouth sores include:

  • avoiding hot foods and beverages
  • chewing carefully and slowly
  • practicing good dental hygiene
  • decreasing stress
  • avoiding smoking and other tobacco use
  • limiting or avoiding alcohol consumption
  • drinking plenty of water
  • speaking to a dentist if a dental device is causing irritation
  • using barrier protection during sex
  • using lip balms with SPF to avoid sun damage

When to see a doctor

A person should speak to a healthcare professional if they experience:

  • sores that get worse or do not get better over time
  • signs of an infection
  • white patches on the sores
  • sores that develop after starting medication or cancer treatment


Mouth sores can be bothersome and painful. There are many causes of mouth sores, the most common of which is irritation.

In many cases, mouth sores will heal on their own with little need for treatment. In other cases, a person may need to take medication to treat the underlying cause of the sores.

If a person has frequent or long-lasting mouth sores or the pain is severe, it is best to speak to a doctor.