I find patients are frequently confused by these lesions and often use these terms interchangeably. Canker Sores (recurrent aphthous ulcers) and Cold Sores (recurrent herpes labialis) are two different ailments and require different treatments. While these conditions are usually not serious, they are very common and painful.
A Canker Sore is an intraoral sore usually located on the cheeks, tongue or floor of the mouth. Typically it is a small, round ulcerated lesion surrounded by a red halo. It is not contagious and its cause is usually multifactorial. Stress, trauma such as cheek biting, some food allergies, smoking and sodium lauryl sulfate (a foaming agent in many toothpastes) all have been implicated as causative factors.
Cold Sores are extraoral lesions usually located under the nose and around the lips. They start as tiny fluid-filled blisters which break open, coalesce and then crust over. These lesions are contagious, especially when the blisters break open. The cause is the herpes virus (HPV) that was contracted in early childhood. This virus lies dormant until triggered by stress, fatigue, hormonal changes or exposure to sun or wind. 90% of the population tests positive for HPV but only approximately 20% of the population will experience a cold sore outbreak. Cold sores have a tendency to recur in more or less the same place each time. Such recurrences may happen often (once a month) or occasionally, (once or twice a year).
Treatment and Prevention to follow.