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25 November 2022

Blister in Mouth: Causes and Treatment

Blisters in the mouth are sores which may appear on soft tissues such as the gums, lips, tongue and the inside of the cheeks. They are quite common and usually disappear within a week or two.

However, these sores can make it uncomfortable when eating and drinking, and sometimes when swallowing.

While most mouth sores do not carry any long-term harm to your health, more severe or recurring types of sores may need medical attention. Sores are usually different in color to the surrounding tissues. Depending on the type of sore and its cause, this color could be white, red, yellow or purple.

Blister in Mouth: What Are the Main Causes?

Mouth blisters can be caused by a variety of reasons. Some of these are down to lifestyles and bad habits, while others could be down to underlying health issues and exposure to certain viruses. The following are some of the more common causes of a mouth blister.

  • Stress
  • Aggressive brushing using a hard-bristled toothbrush
  • Biting the inside of your mouth
  • Tobacco
  • Burning the mouth when eating
  • Hormones
  • Orthodontic devices such as braces that irritate the soft tissues in the mouth

The health issues and viruses which increase your risk from sores include:

  • Crohn’s disease
  • Anemia
  • HIV and Aids
  • Human Papilloma Virus
  • Herpes Simplex Virus
  • Mononucleosis
  • Irritable bowel syndrome

These are some of the contributing risk factors for developing blisters in the mouth. Different types of sores can have different causes and therefore it is useful to consider the main types of mouth blisters.

Common Types of Mouth Blisters

Canker Sores

This common form of blistering can affect up to 20% of people. Although they can be painful, they are harmless and should disappear within a week or two. Canker sores tend to be red and can have white, gray or yellow areas within them.

This form of sore is not contagious and may result from biting the inside of your mouth or gums. A weakened immune system can also increase your risk from canker sores, as can stress, Crohn’s disease and irritable bowel syndrome.

Cold Sores

This is another common type of mouth blister that can affect up to 40% of people. Often red in color, they are normally located near the mouth and on the lips. Unlike canker sores, cold sores are contagious and can be transmitted through kissing and sharing food and utensils.

Cold sores are caused by the herpes simplex virus. Stress and a weakened immune system can contribute to cold sores, as can overexposure to the sun. A tingling or burning sensation may forewarn you of cold sores. These blisters can last for up to six weeks.

Oral Thrush

Symptoms of oral thrush include creamy white blisters on the tongue or soft tissues in the mouth which could be scraped off. Oral thrush is caused by excess candida, a naturally occurring yeast within the body. It does not look too pretty when sticking your tongue out but can usually be cleared within a week or two using anti-fungal medication.

Oral thrush does not tend to be contagious, although it is best to be careful if you have such blistering. Someone with thrush can experience pain when eating, and they may also struggle to taste their food.


This form of sore is most likely to be seen in children. It can seem similar to canker sores, and forms on the gums or on the inside of the cheeks. The sores can be caused by a bacterial or viral infection, and can often be the result of poor oral hygiene. They can last up to three weeks.


This form of mouth blister involves white patches develop on the soft tissues. It is mostly associated with smoking and those who use tobacco products.

Generally, this type of sore is harmless and will clear up of its own accord. However, in some instances it can increase the risk of developing oral cancer.

Oral Cancer

Ulcers or red and white sores in the mouth or on the lips which do not heal or go away can be a sign of oral cancer. Your dentist can check for oral cancer and perform a biopsy to check for cancerous cells. Early detection of cancer helps with treatment and increases the chance of a more successful outcome.

Treating Mouth Sores

Mouth sores usually clear within a couple of weeks. To relieve any pain when you have mouth sores you should avoid hot and spicy foods, as well as tobacco and alcohol. Cold foods such as ice pops may help soothe the area around the blistering.

Additionally, you can gargle with warm saltwater a few times throughout the day. Over-the-counter pain relief can also be useful in combating any discomfort caused by a mouth blister. One thing you should avoid is the temptation to squeeze or pick at a sore.

While most mouth sores will not require a medical diagnosis, if they persist or are severe then you should consult a doctor. You might be prescribed medication to treat any blistering caused by an infection. A doctor may also prescribe pain relief, anti-inflammatory medication or a steroid gel.


While prevention is better than cure, mouth sores are hard to prevent completely. However, some tips to help avoid them include:

  • Good oral hygiene, including regular dental appointments
  • Use a soft-bristled toothbrush
  • A balanced, nutritious diet
  • Stay hydrated
  • Avoid hot, spicy foods
  • Avoid tobacco and limit alcohol
  • Practice ways to reduce stress, such as meditation
  • Protect the lips with lip balm from exposure to the sun
  • Chew slowly
  • Do not bite or chew the inside of the mouth

Mouth blisters or sores are pretty common. While they can be uncomfortable, most clear up within a week or two. However, if they persist, recur or present more severe symptoms you should consult with your doctor, as it could be a sign of a more serious condition.


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