Canker Sores:  an ulceration, especially of the lip or oral mucosa.  This mouth ulcer (canker sore) can be very painful.  Canker sore should heal within two weeks, if the sores last a long time, or you are unable to eat, sleep, or speak properly, you should see your doctor or dentist promptly.

Cause:  The cause is unknown.  Professionals believe that  they usually result from trauma, such as biting the cheek, rather than from infection, along with bad habits, heredity, food, overenthustiastic tooth brushing, and emotional stress are also associated with canker sores.  Some gets it more often than others, there's no good explanation why some some people get them so frequently.

Symptoms: 

Ulceration to lips or oral mucosa  (usually lasting10 to 15 days)

Pain

'Burning' feeling to affected area

Treatment:

Over-the counter medication such as Orabase or Zilactin

Cabamide peroside cankercide:  a combination of  glycerin and peroside which is over the counter - brand names:  Gly-oxide, Amosan, and Cankaid

Other OTC canker sore medications that contain benzocaine, menthol, camphor, eucalyptol, and or alcohol in a liquid or gel.

For those whose sores are extreme and last longer then 2 weeks, see your doctor or dentist - He may prescribed Temovate - a very potent steroid ointment, which usually clears up canker sores quickly.

Vitamin C is known to help with canker sores

Avoid irritation:  Spices, citrus fruit, nuts high in the amino acid arginine (such as walnuts), chocolate, strawberries, and coffee can irritate canker sores and  cause them in some patients.

Home remedies:  Tea bag-  apply a wet black tea bag to the ulcer.  Black tea contains tannin, an astringent (tanac is an OTC medication that contains tannin)

Try 1 tablespoon of hydrogen peroxide in a glass of water and swish it around in your mouth to disinfect the sore and speed up healing.  (don't swallow)

Mylanta:  try to swish mylanta or milk of magnesia around your mouth and allow it to protectively coat the sore (may also contain some antibacterial effect)

Yogurt:  is believe to be helpful in fighting bacteria and help prevent canker sores (yogurt that contains active cultures of Lactobacillus acidophilus) -eat your yogurts