Canker sore and cold sore are often mistaken to be same. Cold sore are caused by herpes virus and canker sore occur inside the mouth and cold sore occur outside the mouth. Factors that cause canker sore are stress, allergies, trauma, vitamin deficiency or iron and some may also have it because it is heredity too. Cold sores are every contagious. Canker sores heal in 8-10 days and cold sores take a weeks time to heal. Non-prescription topical ointments and pain relievers can provide temporary relief to canker sores, whereas for cold sores prescription is required for antiviral drugs. Rinsing with antimicrobial mouth rinses may help reduce the irritation for canker sores. There is no as such cure for cold sores so it reoccurs whenever there is an emotional imbalance or allergies, exposure to sunlight or fever.