Canker sore: MedlinePlus Medical Encyclopedia

P A canker sore is a painful, open sore in the mouth. Canker sores are white or yellow and surrounded by a bright red area. They are not cancerous.
P A canker sore is not the same as a fever blister (cold sore).

T Causes
P Canker sores are a common form of mouth ulcer. They may occur with viral infections. In some cases, the cause is unknown.
P Canker sores may also be linked to problems with the body's immune system. The sores may also be brought on by:
- Mouth injury from dental work
- Cleaning the teeth too roughly
- Biting the tongue or cheek
P Other things that can trigger canker sores include:
- Emotional stress
- Lack of certain vitamins and minerals in the diet (especially iron, folic acid, or vitamin B-12)
- Hormonal changes
- Food allergies
P Anyone can develop a canker sore. Women are more likely to get them than men. Canker sores may run in families.

T Symptoms
P Canker sores most often appear on the inner surface of the cheeks and lips, tongue, upper surface of the mouth, and the base of the gums.
P Symptoms include:
- One or more painful, red spots or bumps that develops into an open ulcer
- White or yellow center
- Small size (most often under one third inch or 1 centimeter across)
- Gray color as healing starts
P Less common symptoms include:
- Fever
- General discomfort or uneasiness (malaise)
- Swollen lymph nodes
P Pain often goes away in 7 to 10 days. It can take 1 to 3 weeks for a canker sore to completely heal. Large ulcers can take longer to heal.

T Exams and Tests
P Your health care provider can often make the diagnosis by looking at the sore.
P If canker sores persist or continue to return, tests should be done to look for other causes, such as erythema multiforme, drug allergies, herpes infection, and bullous lichen planus.
P You may need further testing or a biopsy to look for other causes of mouth ulcers. Canker sores are not cancer and do not cause cancer. There are types of cancer, however, that may first appear as a mouth ulcer that does not heal.

T Treatment
P In most cases, the canker sores go away without treatment.
P Try not to eat hot or spicy foods, which can cause pain.
P Use over-the-counter medicines that ease pain in the area.
- Rinse your mouth with salt water or mild, over-the-counter mouthwashes. (DO NOT use mouthwashes that contain alcohol which can irritate the area more.)
- Apply a mixture of half hydrogen peroxide and half water directly to the sore using a cotton swab. Follow by dabbing a small amount of Milk of Magnesia on the canker sore afterward. Repeat these steps 3 to 4 times a day.
- Rinse your mouth with a mixture of half Milk of Magnesia and half Benadryl liquid allergy medicine. Swish mixture in the mouth for about 1 minute and then spit out.
P Medicines prescribed by your provider may be needed for severe cases. These may include:
- Chlorhexidine mouthwash
- Stronger medicines called corticosteroids that are placed on the sore or are taken in pill form
P Brush your teeth twice a day and floss your teeth every day. Also, get routine dental check-ups.
P In some cases, gastric acid-reducing medicines can decrease the discomfort. 

T Outlook (Prognosis)
P Canker sores almost always heal on their own. The pain should decrease in a few days. Other symptoms disappear in 10 to 14 days.

T When to Contact a Medical Professional
P Call your provider if:
- A canker sore or mouth ulcer does not go away after 2 weeks of home care or gets worse.
- You get canker sores more than 2 or 3 times a year.
- You have symptoms with the canker sore such as fever, diarrhea, headache, or skin rash.

T Alternative Names
P Aphthous ulcer; Ulcer - aphthous

T Images
- Canker sore
- Mouth anatomy
- Canker sore (aphthous ulcer)
- Fever blister

T References
P Bope ET, Kellerman RD. Diseases of the skin. In: Bope ET, Kellerman RD, eds. Conn's Current Therapy 2017. Philadelphia, PA: Elsevier; 2017:chap 14.
P Chattopadhyay A, Shetty, KV. Recurrent aphthous stomatitis. Otolaryngol Clin North Am. 2011;44(1):79-88. PMID: 21093624 www.ncbi.nlm.nih.gov/pubmed/21093624.
P Daniels TE, Jordan RC. Diseases of the mouth and salivary glands. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 425.
P Lingen MW. Head and neck. In: Kumar V, Abbas AK, Aster JC, eds. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 16. 

T Review Date 4/3/2017
P Updated by: Josef Shargorodsky, MD, MPH, Johns Hopkins University School of Medicine, Baltimore, MD. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

