Canker sores (apthous ulcers) are often confused with fever blisters (cold sores). They are quite different, however. Canker sores are only found inside the mouth on the gums, cheeks, tongue or floor of the mouth. They cannot be transmitted from one individual to another.
Canker sores begin as small red circular swellings that usually ulcerate (rupture) within a day, after which they become white, surrounded by reddish inflammation. They last 8-10 days. As open sores, they can be very painful to the touch. Canker sores afflict about 20 percent of the population. Their cause has yet to be discovered, although they appear to break out more in stressful situations, from getting a small "nick" in the skin (mucous membrane) inside the mouth or from foods such as citrus fruits and tomatoes. While they can occur in very young children, they are usually first seen between the ages of 10 and 20. It's not uncommon for them to erupt three to four times a year, but they occur less frequently or stop altogether in adults.
When experiencing canker sores, avoid rough textured or spicy foods that will irritate them. Try not to touch them with eating utensils or your toothbrush. Apply ointment that contains a topical anesthetic or some other active ingredient that will relieve the irritation or call your dentist for some recommendations.
Cold sores are found outside the mouth, usually on the lips but may appear on the chin, outside of the cheek or the nostrils. They begin as a red blister, burst and crust over. The cycle takes 7-14 days to heal. Cold sores, caused by the herpes simplex virus, are contagious and are transmitted by skin-to-skin contact. The virus is dormant most of the time and is carried by almost everyone. Fever blisters occur most often in young adults and adolescents and decline in people over 35 years of age. Certain factors activate their outbreak, particularly stress, colds, fevers and/or sunburn.
To reduce occurrences, avoid kissing when the blisters are visible; don't squeeze or scrape the blister; wash your hands thoroughly before touching someone else; and use UV sunscreen on your lips before spending time in the sun.
Treatment of cold sores include avoiding spicy and hot foods, applying prescription based or over-the-counter ointments containing phenol and administering some anti-viral antibiotics that will shorten their duration.